Articles de revues : « Photosynthetic parameter »

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Huot, Y., M. Babin et F. Bruyant. « Photosynthetic parameters in the Beaufort Sea in relation to the phytoplankton community structure ». Biogeosciences Discussions 10, n^o 1 (30 janvier 2013) : 1551–76. http://dx.doi.org/10.5194/bgd-10-1551-2013.

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Abstract. To model phytoplankton primary production from remotely sensed data a method to estimate photosynthetic parameters describing the photosynthetic rates per unit biomass is required. Variability in these parameters must be related to environmental variables that are measurable remotely. In the Arctic, a limited number of measurements of photosynthetic parameter have been carried out with the concurrent environmental variables needed. Therefore, to improve the accuracy of remote estimates of phytoplankton primary production as well as our ability to predict changes in the future such measurements and relationship to environmental variables are required. During the MALINA cruise, a large dataset of these parameters were obtained. Together with previously published datasets, we use environmental and trophic variables to provide functional relationships for these parameters. In particular, we describe several specific aspects: the maximum rate of photosynthesis (Pmaxchl) normalized to chlorophyll decreases with depth and is higher for communities composed of large cells; the saturation parameter (Ek) decreases with depth but is independent of the community structure; and the initial slope of the photosynthesis versus irradiance curve (αchl) normalized to chlorophyll is independent of depth but is higher for communities composed of larger cells. The photosynthetic parameters were not influenced by temperature over the range encountered during the cruise (−2 to 8 °C).

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Jasper, Stephen, et Max L. Bothwell. « Photosynthetic Characteristics of Lotic Periphyton ». Canadian Journal of Fisheries and Aquatic Sciences 43, n^o 10 (1 octobre 1986) : 1960–69. http://dx.doi.org/10.1139/f86-241.

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Periphyton communities, grown in continuous-flow troughs, were suspended in filtered river water and placed in a photosynthesis–light incubator similar to those used for phytoplankton. A three-parameter equation was fitted to the incubator data. Seasonally the initial slope, α, ranged from 12.1 to 53.6 μg C∙(mg Chl a)−1∙h−1∙(μEinst.∙m−2∙s−1)−1; the maximum photosynthetic rate, PBmax, varied from 1.16 to 5.49 mgC∙(mg Chl a)−1∙h−1; and the inhibition parameter, Ib, ranged from 1500 to 6900 μEinst.∙m−2∙s−1. These values are similar to those reported for other periphyton and phytoplankton. PBmax strongly correlated with light history, whereas inhibition was inversely related to water temperature, α did not correlate with either irradiance or temperature but with changes in average cell size. Seasonal variations in the light level optimal for photosynthesis, Im, suggested a period in late winter and early spring for potentially serious inhibition of photosynthesis. These Chl a normalized photosynthetic parameters were unaffected by changes in concentration of the growth-limiting nutrient, phosphorus.

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Huot, Y., M. Babin et F. Bruyant. « Photosynthetic parameters in the Beaufort Sea in relation to the phytoplankton community structure ». Biogeosciences 10, n^o 5 (29 mai 2013) : 3445–54. http://dx.doi.org/10.5194/bg-10-3445-2013.

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Abstract. To model phytoplankton primary production from remotely sensed data, a method to estimate photosynthetic parameters describing the photosynthetic rates per unit biomass is required. Variability in these parameters must be related to environmental variables that are measurable remotely. In the Arctic, a limited number of measurements of photosynthetic parameters have been carried out with the concurrent environmental variables needed. Such measurements and their relationship to environmental variables will be required to improve the accuracy of remotely sensed estimates of phytoplankton primary production and our ability to predict future changes. During the MALINA cruise, a large dataset of these parameters was obtained. Together with previously published datasets, we use environmental and trophic variables to provide functional relationships for these parameters. In particular, we describe several specific aspects: the maximum rate of photosynthesis (Pmaxchl) normalized to chlorophyll decreases with depth and is higher for communities composed of large cells; the saturation parameter (Ek) decreases with depth but is independent of the community structure; and the initial slope of the photosynthesis versus irradiance curve (αchl) normalized to chlorophyll is independent of depth but is higher for communities composed of larger cells. The photosynthetic parameters were not influenced by temperature over the range encountered during the cruise (−2 to 8 °C).

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Vieira Jr., Jair, et Orlando Necchi Jr. « Photosynthetic characteristics of a tropical population of Nitella cernua (Characeae, Chlorophyta) ». Brazilian Journal of Plant Physiology 18, n^o 3 (septembre 2006) : 379–88. http://dx.doi.org/10.1590/s1677-04202006000300004.

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Photosynthetic characteristics (assessed by chlorophyll fluorescence and O2 evolution) were analysed monthly during one year in a tropical population of Nitella cernua from southeastern Brazil (20º50'32" S, 49º26'15" W). Parameters derived from photosynthesis-irradiance (PI) curves by fluorescence (high values of the photosynthetic parameter, Ik, and lack or low values of photoinhibition, beta) suggested adaptation to high irradiance, whereas those by O2 evolution showed a different pattern (low values of Ik and compensation irradiance, Ic, high values of photosynthetic efficiency, alpha, and photoinhibition). Parameters from PI curves by O2 evolution suggested light acclimation: Ik and maximum photosynthetic rate, Pmax (as rETR, relative electron transfer rate) increased, whereas a became significantly lower under higher irradiance (winter). This pattern is an adjustment of both number and size of photosynthetic units. Photosynthetic performance assessed by fluorescence revealed two seasonal periods: higher values of Pmax (rETR), Ik and non-photochemical quenching from October to March (rainy season), and lower values from April to October (dry season). Temperature responses were observed only in summer, but temperature optima were different between methods: peaks of net photosynthesis occurred at 20ºC, whereas rETR increased towards higher temperatures (up to 30ºC). Dark respiration increased with higher temperatures. Current velocity had a stimulatory effect on photosynthetic rates, as suggested by positive correlations with Pmax (rETR) and alpha. pH experiments revealed highest net photosynthetic rates under pH 4.0, suggesting higher affinity for CO2 than HCO3-. This broad range of responses of photosynthetic characteristics of this N. cernua population to irradiance, temperature, and pH/inorganic carbon reflects a wide tolerance to variations in these environmental variables, which probably contribute to the wide distribution of this species.

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Ma, Xuemei, Qiang Liu, Zhidong Zhang, Zewen Zhang, Zeyu Zhou, Yu Jiang et Xuanrui Huang. « Effects of photosynthetic models on the calculation results of photosynthetic response parameters in young Larix principis-rupprechtii Mayr. plantation ». PLOS ONE 16, n^o 12 (31 décembre 2021) : e0261683. http://dx.doi.org/10.1371/journal.pone.0261683.

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Accurately predicting the crown photosynthesis of trees is necessary for better understanding the C circle in terrestrial ecosystem. However, modeling crown for individual tree is still challenging with the complex crown structure and changeable environmental conditions. This study was conducted to explore model in modeling the photosynthesis light response curve of the tree crown of young Larix principis-rupprechtii Mayr. Plantation. The rectangular hyperbolic model (RHM), non-rectangular hyperbolic model (NRHM), exponential model (EM) and modified rectangular hyperbolic model (MRHM) were used to model the photosynthetic light response curves. The fitting accuracy of these models was tested by comparing determinants coefficients (R2), mean square errors (MSE) and Akaike information criterion (AIC). The results showed that the mean value of R2 of MRHM (R2 = 0.9687) was the highest, whereas MSE value (MSE = 0.0748) and AIC value (AIC = -39.21) were the lowest. The order of fitting accuracy of the four models for Pn-PAR response curve was as follows: MRHM > EM > NRHM > RHM. In addition, the light saturation point (LSP) obtained by MRHM was slightly lower than the observed values, whereas the maximum net photosynthetic rates (Pmax) modeled by the four models were close to the measured values. Therefore, MRHM was superior to other three models in describing the photosynthetic response curve, the accurate values were that the quantum efficiency (α), maximum net photosynthetic rate (Pmax), light saturation point (LSP), light compensation point (LCP) and respiration rate (Rd) were 0.06, 6.06 μmol·m-2s-1, 802.68 μmol·m-2s-1, 10.76 μmol·m-2s-1 and 0.60 μmol·m-2s-1. Moreover, the photosynthetic response parameters values among different layers were also significant. Our findings have critical implications for parameter calibration of photosynthetic models and thus robust prediction of photosynthetic response in forests.

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Yin, Xiaohong, Xing Li, Jiaxin Xie, Zhengwu Xiao, Chunrong Zhao, Yuling Kang, Chuanming Zhou, Fangbo Cao, Jiana Chen et Min Huang. « Do You Get What You Pay for ? Evaluating the Reliability of an Inexpensive Portable Photosynthesis System in Measuring Gas Exchange in Rice (Oryza sativa L.) Leaves ». Agronomy 12, n^o 11 (7 novembre 2022) : 2775. http://dx.doi.org/10.3390/agronomy12112775.

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The availability of commercially available portable photosynthesis systems has facilitated widespread photosynthetic research. Our study aimed to evaluate the reliability of a recently developed inexpensive portable photosynthesis system, Yaxin-1105, in measuring gas exchange in rice (Oryza sativa L.) leaves. Gas exchange parameters, including net photosynthetic rate (Anet), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (E), were measured on 88 rice leaves across seven rice cultivars and three growth stages (panicle initiation, heading, and early ripening), using both Yaxin-1105 and LI-6400XT. There were significant difference between each gas exchange parameter at each growth stage measured by Yaxin-1105 and LI-6400XT, except Ci at the heading stage. Mean Anet, gs, and E measured by Yaxin-1105 were 26–66% lower than those measured by LI-6400XT at panicle initiation, heading, and early ripening stages. Mean Ci measured by Yaxin-1105 was 13–22% higher than that measured by LI-6400XT at panicle initiation and early ripening stages. The coefficients of determination between each gas exchange parameter measured by Yaxin-1105 and by LI-6400XT at panicle initiation, heading, and early ripening stages ranged from only 0.0007 to 0.1889. These results indicate that the Yaxin-1105 is not a reliable tool for measuring gas exchange in rice leaves.

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RACZ, Ionuț, Rozalia KADAR, Diana HIRISCǍU, Marius BǍRDAŞ, Florin Dumitru BORA, Camelia URDǍ et Adina TǍRǍU. « Evaluation of Photosynthesis Capacity of Some Winter Wheat Genotypes in Transylvanian Plain Conditions ». Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Agriculture 75, n^o 1 (18 mai 2018) : 56. http://dx.doi.org/10.15835/buasvmcn-agr:004617.

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Leaf photosynthetic capacity is a key parameter determining crop yield; it is enhanced by moderate soil moisture and reduced in both severe water deficit and excessive water conditions. The aim of this work was to evaluate the wheat variety photosynthetic capacity in two main phenological stages. The evaluation of photosynthesis capacity of studied winter wheat varieties in Transylvanian Plain conditions offer relevant information on Romanian genetic material type and paving the way of new research directed to a new wheat breeding program criteria and for improvement of those.

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Sun, Zhongqiu, Songxi Yang, Shuo Shi et Jian Yang. « The Effect of Principal Component Analysis Parameters on Solar-Induced Chlorophyll Fluorescence Signal Extraction ». Applied Sciences 11, n^o 11 (26 mai 2021) : 4883. http://dx.doi.org/10.3390/app11114883.

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Solar-induced chlorophyll fluorescence (SIF), one of the three main releasing pathways of vegetation-absorbed photosynthetic active radiation, has been proven as an effective monitoring implementation of leaf photosynthesis, canopy growth, and ecological diversity. There exist three categories of SIF retrieval methods, and the principal component analysis (PCA) retrieval method is obtrusively eye-catching due to its brief, data-driven characteristics. However, we still lack a lucid understanding of PCA’s parameter settings. In this study, we examined if principal component numbers and retrieval band regions could have effects on the accuracy of SIF inversion under two controlled experiments. The results revealed that the near-infrared region could remarkably boost SIF’s retrieval accuracy, whereas red and near-infrared bands caused anomalous values, which subverted a traditional view that more retrieval regions might provide more photosynthetic information. Furthermore, the results demonstrated that three principal components would benefit more in PCA-based SIF retrieval. These arguments further help elucidate the more in-depth influence of the parameters on the PCA retrieval method, which unveil the potential effects of different parameters and give a parameter-setting foundation for the PCA retrieval method, in addition to assisting retrieval achievements.

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Osei-Kwarteng, Mildred, Emmanuel Ayipio, Dany Moualeu-Ngangue, Gerhard Buck-Sorlin et Hartmut Stützel. « Interspecific variation in leaf traits, photosynthetic light response, and whole-plant productivity in amaranths (Amaranthus spp. L.) ». PLOS ONE 17, n^o 6 (30 juin 2022) : e0270674. http://dx.doi.org/10.1371/journal.pone.0270674.

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Photosynthetic light response curve parameters help us understand the interspecific variation in photosynthetic traits, leaf acclimation status, carbon uptake, and plant productivity in specific environments. These parameters are also influenced by leaf traits which rely on species and growth environment. In accessions of four amaranth species (Amaranthus. hybridus, A. dubius, A. hypochondriacus, and A. cruentus), we determined variations in the net photosynthetic light response curves and leaf traits, and analysed the relationships between maximum gross photosynthetic rate, leaf traits, and whole-plant productivity. Non-rectangular hyperbolae were used for the net photosynthesis light response curves. Maximum gross photosynthetic rate (Pgmax) was the only variant parameter among the species, ranging from 22.29 to 34.21 μmol m–2 s–1. Interspecific variation existed for all the leaf traits except leaf mass per area and leaf inclination angle. Stomatal conductance, nitrogen, chlorophyll, and carotenoid contents, as well as leaf area correlated with Pgmax. Stomatal conductance and leaf nitrogen explained much of the variation in Pgmax at the leaf level. At the plant level, the slope between absolute growth rate and leaf area showed a strong linear relationship with Pgmax. Overall, A. hybridus and A. cruentus exhibited higher Pgmax at the leaf level and light use efficiency at the whole-plant level than A. dubius, and A. hypochondriacus. Thus, A. hybridus and A. cruentus tended to be more efficient with respect to carbon assimilation. These findings highlight the correlation between leaf photosynthetic characteristics, other leaf traits, and whole plant productivity in amaranths. Future studies may explore more species and accessions of Amaranthus at different locations or light environments.

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Manojkumar, K., S. Vincent, M. Raveendran, R. Anandham, V. Babu Rajendra Prasad, A. Mothilal et S. Anandakumar. « Effect of drought on gas exchange and chlorophyll fluorescence of groundnut genotypes ». Journal of Applied and Natural Science 13, n^o 4 (16 décembre 2021) : 1478–87. http://dx.doi.org/10.31018/jans.v13i4.3145.

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Drought is one of the major threats to groundnut productivity, causing a greater loss than any other abiotic factor. Water stress conditions alter plant photosynthetic activity, impacting future growth and assimilating mobilization towards sink tissues. The purpose of this study was to investigate how drought impacts the photosynthesis of plants and its links to drought tolerance. The influence of reproductive stage drought on photosynthetic activity and chlorophyll fluorescence of groundnut is well studied. The experiment was conducted in Kharif 2019 (Jul-Sep), where recent series in groundnut genotypes (60 nos) sown under rainfed conditions and water stress was created by withholding irrigation for 20 days between 35-55 days after sowing in the field to simulate drought conditions. Imposition of water deficit stress reduced PS II efficiency, which significantly altered the photosynthetic rate in the leaf. Observation of gas exchange parameters viz., photosynthetic rate, stomatal conductance and transpiration rate after 20 days of stress imposition revealed that of all 60 genotypes, 20 genotypes (VG 17008, VG 17046VG 18005, VG 18102, VG 18077, VG 19572, VG 19709, VG 18111, VG19561, VG19576, VG 19620, VG 19681, VG 19688, etc.,) had better Photosynthetic rate, Stomatal conductance. Similarly, PS II efficiency analyzed through fluorescence meter revealed that among the 60 and all the genotypes given above recorded higher value in Fv/Fm. Results obtained from Cluster analysis and PCA confirmed that photosynthetic rate and Fv/Fm is useful parameter in screening adapted cultivars under drought stress. These findings lay the groundwork for a future study to decipher the molecular pathways underpinning groundnut drought resistance.

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Liang, Le, Qiaoman Ao, Ying Zhu, Yan Zhao, Ran Zhang et Yi Tang. « The influence of application hyperaccumulator plant straw on photosynthetic pigment content and photosynthetic parameter of lettuce under cadmium stress ». E3S Web of Conferences 136 (2019) : 07007. http://dx.doi.org/10.1051/e3sconf/201913607007.

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Pot experiments were conducted to study the effects of straw application of three hyperaccumulator plants (Solanum nigrum, Bidens pilosa and Galinsoga parviflora) influence photosynthetic pigments content and photosynthetic parameters of lettuce (Lactuca sativa) under Cd stress. The results showed that: compared with no straw application, the photosynthetic pigment content of lettuce was increased by applying three kinds of hyperaccumulator plants straw (S. nigrum, B. pilosa and G. parviflora), but there was no significant difference among the three kinds of hyperaccumulator plant straws; also improved the net photosynthetic rate (Pn), Stomatal conductance (Gs), transpiration rate (Tr), intercellular CO2 concentration (Ci) of lettuce, among them, the effect of G. parviflora straw was the most obvious. Application of three kinds of hyperaccumulator plant straw promoted the growth of lettuce by increasing the photosynthetic pigment content and photosynthetic parameter of lettuce under Cd stress.

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Chen, Xinyan, Zhaohui Jiang, Qile Tai, Chunshan Shen, Yuan Rao et Wu Zhang. « Construction of a photosynthetic rate prediction model for greenhouse strawberries with distributed regulation of light environment ». Mathematical Biosciences and Engineering 19, n^o 12 (2022) : 12774–91. http://dx.doi.org/10.3934/mbe.2022596.

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<abstract> In winter and spring, for greenhouses with larger areas and stereoscopic cultivation, distributed light environment regulation based on photosynthetic rate prediction model can better ensure good crop growth. In this paper, strawberries at flowering-fruit stage were used as the test crop, and the LI-6800 portable photosynthesis system was used to control the leaf chamber environment and obtain sample data by nested photosynthetic rate combination experiments under temperature, light and CO2 concentration conditions to study the photosynthetic rate prediction model construction method. For a small-sample, nonlinear real experimental data set validated by grey relational analysis, a photosynthetic rate prediction model was developed based on Support vector regression (SVR), and the particle swarm algorithm (PSO) was used to search the influence of the empirical values of parameters, such as the penalty parameter <italic>C</italic>, accuracy <italic>ε</italic> and kernel constant <italic>g</italic>, on the model prediction performance. The modeling and prediction results show that the PSO-SVR method outperforms the commonly used algorithms such as MLR, BP, SVR and RF in terms of prediction performance and generalization on a small sample data set. The research in this paper achieves accurate prediction of photosynthetic rate of strawberry and lays the foundation for subsequent distributed regulation of greenhouse strawberry light environment. </abstract>

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Tanneru, Hemanth Kumar, Resmi Suresh, Aravind Vyas Ramanan, Shahparnia Mehdi, Muthukumaran Packirisamy, Pragasen Pillay, Sheldon Williamson, Philippe Juneau et Raghunathan Rengaswamy. « Micro photosynthetic cell for power generation from algae : Bio-electrochemical modeling and verification ». TECHNOLOGY 04, n^o 04 (décembre 2016) : 249–58. http://dx.doi.org/10.1142/s2339547816500114.

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A simple first-principles mathematical model is developed to predict the performance of a micro photosynthetic power cell ([Formula: see text]PSC), an electrochemical device which generates electricity by harnessing electrons from photosynthesis in the presence of light. A lumped parameter approach is used to develop a model in which the electrochemical kinetic rate constants and diffusion effects are lumped into a single characteristic rate constant [Formula: see text]. A non-parametric estimation of [Formula: see text] for the [Formula: see text]PSC is performed by minimizing the sum square errors (SSE) between the experimental and model predicted current and voltages. The developed model is validated by comparing the model predicted [Formula: see text] characteristics with experimental data not used in the parameter estimation. Sensitivity analysis of the design parameters and the operational parameters reveal interesting insights for performance enhancement. Analysis of the model also suggests that there are two different operating regimes that are observed in this [Formula: see text]PSC. This modeling approach can be used in other designs of [Formula: see text]PSCs for performance enhancement studies.

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Baker, Jeffrey T., Marvin L. Baker, D. Ron Earhart, Leonard M. Pike, Kil S. Yoo et Roger Horns. « Photosynthetic Light Response of Six Clonal Selections of the Sweet Potato Cultivar `Beauregard' ». HortScience 33, n^o 4 (juillet 1998) : 605f—606. http://dx.doi.org/10.21273/hortsci.33.4.605f.

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Eight individual potatoes, exhibiting a wide range of quality characteristics, were cloned at the Texas A&M Vegetable Improvement Center, College Station, Tex., in order to produce a large number of slips for field trials. Leaf photosynthetic light response for six of these clonal selections was determined during a greenhouse experiment conducted at the Texas A&M Univ. Agricultural Research and Extension Center at Overton, Tex. Photosynthesis data were fit to a rectangular hyperbola in order to estimate light saturated leaf photosynthetic rate (Amax), quantum efficiency (QE), and dark respiration rate (Rd). Significant differences (P ≥ 0.05) were detected in all three of these parameter estimates among the six clonal selections. Parameter estimates ranged from 23.4 to 28.8 μmol (CO2) m-2·s-1, 0.056 to 0.071 mol (CO2)/mol (photons), and –0.9 to –2.0 μmol (CO2) m-2·s-1 for Amax, QE, and Rd, respectively. However, these differences were not clearly related to quality characteristics determined for these clones in field trials.

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Ball, MC, JA Butterworth, JS Roden, R. Christian, JJG Egerton, TJ Wydrzynski, WS Chow et MR Badger. « Applications of Chlorophyll Fluorescence to Forest Ecology ». Functional Plant Biology 22, n^o 2 (1995) : 311. http://dx.doi.org/10.1071/pp9950311.

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Functioning of photosystem II (PSII) is the most sensitive indicator of environmental stress in plants. Changes in PSII activity can be assayed rapidly and non-destructively by measurement of chlorophyll fluorescence. While there have been many laboratory studies of chlorophyll fluorescence, fluorescence techniques have seldom been applied to questions in forest ecology. Most studies have emphasised the fluorescence parameter, Fv/Fm, which is well correlated with the quantum efficiency of photosynthetic carbon dioxide assimilation or oxygen evolution. This parameter reveals information which can be related to diurnal and seasonal variation in photosynthesis, plant growth and community dynamics. Thus, fluorescence techniques provide a powerful means of linking photosynthesis with higher levels of plant functioning and have great potential for research in forest ecology.

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Kozyreva, M. Iu, et L. Zh Basieva. « PHOTOSYNTHETIC PARAMETERS OF ALFALFA CROPS IN RELATION TO THE TYPE OF NITROGEN NUTRITION ». Bulletin of NSAU (Novosibirsk State Agrarian University), n^o 2 (15 juillet 2020) : 27–33. http://dx.doi.org/10.31677/2072-6724-2020-55-2-27-33.

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The paper shows the results of field experiments conducted in 2017-2019. The experiments were devoted to photosynthetic indices of alfalfa in relation to the type of nitrogen nutrition and symbiotic activity of crops. The experiments with alfalfa blue-hybrid were carried out in environmental conditions of the piedmont zone of RNO-Alania on chernozem leached soil with close occurrence of gravel. The researchers compared mineral and symbiotrophic types of nitrogen nutrition of alfalfa plants; they applied mineral nitrogen fertilizers and biospecimens on the basis of rizobium. In natural conditions (control group) the crops formed photosynthetic potential from 1701.3 thousand m²-days/ha per year of sowing to 3624.3 thousand m²-days/ha in the second year of sowing. Crop rates in the third year had intermediate values between the first and second years of crop use. The effect of starting doses of nitrogen fertilizers was observed during the sowing year in its early stages, when the symbiotic system is still underdeveloped and inactive. When estimating the annual average photosynthetic potential, starting nitrogen doses gave an advantage of only 1.6%. Presowing inoculation of seeds by active strains of strawberry bacteria provided the maximum positive effect, while high mountain strains of rizobium were more effective. Average annual parameter of photosynthetic potential varied from 2699.1to3189.4 thousand m² days/ha, increasing with the improvement of nitrogen nutrition. Inoculation of seeds by high-altitude strains of tuber bacteria increased photosynthetic potential to its maximum values or by 18.2%. In the same variant, as well as in the variant with the starting dose of nitrogen, the maximum values of net productivity of photosynthesis were achieved, which exceeded the values of the control variant by 0.09-0.11 g/m²- day.

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Bautista, AIN, et O. Necchi-Júnior. « Photoacclimation in a tropical population of Cladophora glomerata (L.) Kützing 1843 (Chlorophyta) from southeastern Brazil ». Brazilian Journal of Biology 68, n^o 1 (février 2008) : 129–36. http://dx.doi.org/10.1590/s1519-69842008000100018.

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Photoacclimation of photosynthesis was investigated in a tropical population of C. glomerata (São Paulo State, southeastern Brazil, 20º 48’ 24" S and 49º 22’ 24" W) by chlorophyll fluorescence parameters and chlorophyll a content. Plants were acclimated to two levels of irradiance: low (65 ± 5 µmol.m-2.s-1) and high (300 ± 10 µmol.m-2.s-1) and exposed short-term (4 days) and long-term (28 days) under a light-dark cycle of 12:12 hours. Photosynthesis-irradiance (PI) curves revealed distinct strategies of photoacclimation. In long-term exposure, plants acclimated by altering the photosynthetic units (PSU) number and keeping fixed the PSU size, revealed by increased rates of maximum photosynthesis (Pmax), lower photosynthetic efficiency (alpha) and higher values of the saturation parameter (Ik) under high irradiance. The short-term acclimation strategy consisted of changing the PSU size, with a fixed number of PSUs, as revealed by similar Pmax but higher alpha and lower Ik under low irradiance. Chlorophyll a contents followed the general pattern reported in green algae of higher concentrations under lower irradiance. Dark/light induction curves revealed consistently higher values of potential quantum yield under low irradiance. Initial and final values showed a higher recovery capacity in the short (84.4-90.6%) term exposure than in the long-term case (81.4-81.5%). ETR (electron transport rate) and NPQ (non-photochemical quenching) values were consistently higher under low irradiance. ETR showed a continuous and steady increase along the light exposure period in the short and long-term experiments, whereas NPQ values revealed a rapid increase after 15 seconds of light exposure, kept a slightly increasing trend and stabilized in most treatments. Lower photosynthetic performance (ETR) and recovery capacity of potential quantum yield were observed, particularly in long-term exposure, suggesting that this population is constrained by the typical high light environment of tropical regions.

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Sun, Jingsong, Jindong Sun et Zhaozhong Feng. « Modelling photosynthesis in flag leaves of winter wheat (Triticum aestivum) considering the variation in photosynthesis parameters during development ». Functional Plant Biology 42, n^o 11 (2015) : 1036. http://dx.doi.org/10.1071/fp15140.

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The Farquhar–von Caemmerer–Berry (FvCB) model of photosynthesis has been widely used to estimate the photosynthetic C flux of plants under different growth conditions. However, the seasonal fluctuation of some photosynthesis parameters (e.g. the maximum carboxylation rate of Rubisco (Vcmax), the maximum electron transport rate (Jmax) and internal mesophyll conductance to CO2 transport (gm)) is not considered in the FvCB model. In this study, we investigated the patterns of the FvCB parameters during flag leaf development based on measured photosynthesis–intercellular CO2 curves in two cultivars of winter wheat (Triticum aestivum L.). Parameterised seasonal patterns of photosynthesis parameters in the FvCB model have subsequently been applied in order to predict the photosynthesis of flag leaves. The results indicate that the Gaussian curve characterises the dynamic patterns of Vcmax, Jmax and gm well. Compared with the model with fixed photosynthesis parameter values, updating the FvCB model by considering seasonal changes in Vcmax and Jmax during flag leaf development slightly improved predictions of photosynthesis. However, if the updated FvCB model incorporated the seasonal patterns of Vcmax and Jmax, and also of gm, predictions of photosynthesis was improved a lot, matching well with the measurements (R2 = 0.87, P < 0.0001). This suggests that the dynamics of photosynthesis parameters, particularly gm, play an important role in estimating the photosynthesis rate of winter wheat.

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Guzzon, Antonella, Francesca Di Pippo et Roberta Congestri. « Wastewater Biofilm Photosynthesis in Photobioreactors ». Microorganisms 7, n^o 8 (10 août 2019) : 252. http://dx.doi.org/10.3390/microorganisms7080252.

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Photosynthetic performance of algal-bacterial biofilms from an Italian wastewater treatment plant was studied in a flow-lane photobioreactor at different irradiances, temperatures, and flow regime to evaluate the effects of these environmental parameters on biofilms’ functioning, in view of application of these communities in wastewater biological treatment. Pulse amplitude modulated fluorescence was used to estimate the effective quantum yield of PSII (ΔF/Fm’) of the light-acclimated biofilms and to perform rapid light curves (RLCs) for the determination of the photosynthetic parameters (rel.ETRmax, α, Ik). Chl a, ash free dry weight (AFDW), and dry weight (DW) were measured to assess phototrophic and whole biofilm biomass development over time. From the analysis of photosynthetic parameter variation with light intensity, temperature and flow rate, it was possible to identify the set of experimental values favoring biofilm photosynthetic activity. Biomass increased over time, especially at the highest irradiances, where substrata were fastly colonized and mature biofilms developed at all temperatures and flow conditions tested.

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Suzuki, Kensaku, et Hidenori Onodera. « Adaptation of a Chlamydomonas mutant with reduced rate of photorespiration to different concentrations of CO2 ». Canadian Journal of Botany 83, n^o 7 (1 juillet 2005) : 834–41. http://dx.doi.org/10.1139/b05-068.

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It has been widely accepted that Chlamydomonas reinhardtii cells utilize inorganic carbon very efficiently for photosynthesis by operating a CO2-concentrating mechanism (CCM) under conditions of limited CO2. To help define the mechanism, 7FR2N, one of the suppressor double mutants of phosphoglycolate phosphatase-deficient (pgp1) mutants that have a reduced photorespiration rate (RPR) was crossed with wild-type strains to generate the strain N21 as a single RPR mutant. The comparison of photosynthetic characteristics with wild-type strains after the cells adapted to different concentrations of CO2 revealed that photosynthetic affinity for inorganic carbon was higher than that in wild-type strains after adaptation to concentrations between 50 µL·L1 CO2 and 5% CO2. Chlorophyll fluorescence parameters were also compared, and the biggest difference between N21 and the wild-type strains was observed in the photochemical quenching and effective quantum yield of photosystem II (ΔF/Fm′) at the CO2 compensation point. These values in N21 increased in a similar manner to the photosynthetic affinity for CO2, and increased significantly when the cells adapted to low-CO2 levels, whereas the values in the wild-type strains were apparently lower without any significant changes, regardless of the CO2 concentrations to which they were adapted. Although it was not clear if a nonphotochemical quenching parameter (NPQ) in N21 was higher than that in wild-type strains, NPQ increased coincidentally with the increase in photosynthetic affinity for inorganic carbon when the CO2 concentrations to which the strains were adapted decreased, in both the mutant and wild-type strain, suggesting that this form of NPQ reflects the operation of CCM in certain conditions. Possible candidates for the RPR mutation and the relationship between CCM and photosynthetic electron flow are discussed.Key words: Chlamydomonas reinhardtii, chlorophyll fluorescence, CO2-concentrating mechanism, low-CO2 responsive gene, phosphoglycolate phosphatase, photorespiration.

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Suriyagoda, Lalith D. B., Hans Lambers, Megan H. Ryan et Michael Renton. « Effects of leaf development and phosphorus supply on the photosynthetic characteristics of perennial legume species with pasture potential : modelling photosynthesis with leaf development ». Functional Plant Biology 37, n^o 8 (2010) : 713. http://dx.doi.org/10.1071/fp09284.

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Age-dependent changes in leaf photosynthetic characteristics (i.e. parameters of the light response curve (maximum photosynthetic rate (Pmax), quantum yield (Φ) and the convexity parameter (θ)), stomatal conductance (gs) and dark respiration rate (Rd)) of an exotic perennial legume, Medicago sativa L. (lucerne), and two potential pasture legumes native to Australia, Cullen australasicum (Schltdl.) J.W. Grime and Cullen pallidum A. Lee, grown in a glasshouse for 5 months at two phosphorus (P) levels (3 (P3) and 30 (P30) mg P kg–1 dry soil) were tested. Leaf appearance rate and leaf area were lower at P3 than at P30 in all species, with M. sativa being the most sensitive to P3. At any leaf age, photosynthetic characteristics did not differ between P treatments. However, Pmax and gs for all the species and Φ for Cullen species increased until full leaf expansion and then decreased. The convexity parameter, θ, did not change with leaf age, whereas Rd decreased. The estimates of leaf net photosynthetic rate (Pleaf) obtained through simulations at variable Pmax and Φ were lower during early and late leaf developmental stages and at lower light intensities than those obtained when Φ was assumed to be constant (e.g. for a horizontally placed leaf, during the 1500°C days developmental period, 3 and 19% reduction of Pleaf at light intensities of 1500 and 500 µmol m–2 s–1, respectively). Therefore, developmental changes in leaf photosynthetic characteristics should be considered when estimating and simulating Pleaf of these pasture species.

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Ferrar, PJ, RO Slatyer et JA Vranjic. « Photosynthetic Temperature Acclimation in Eucalyptus Species From Diverse Habitats, and a Comparison With Nerium oleander ». Functional Plant Biology 16, n^o 2 (1989) : 199. http://dx.doi.org/10.1071/pp9890199.

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The response of net photosynthesis per unit leaf area to growth and measurement temperature was measured for Eucalyptus species from diverse natural habitats in Australia and the results compared to Nerium oleander, a species known to exhibit a large degree of temperature acclimation. Eucalyptus species did not show the same degree of temperature acclimation observed for N. oleander in this and previous studies. Photosynthetic acclimation to temperature varied with species of Eucalyptus, apparently in relation to their subgeneric groupings. The estimated parameter, the preferred temperature for photosynthesis, correlated broadly with temperature conditions in the natural habitat. Estimates of two biochemical parameters, Rubisco (estimated from the initial slope of the A/pI curve) and RuP2 regeneration capacity (calculated from the A/pI curve at high CO2) were found to parallel changes in assimilation rate. High temperature acclimation in the Eucalyptus species differed from that of N. oleander. Low temperature grown species, except E. miniata, had a higher temperature threshold for reversible inactivation of Rubisco. In E. miniata, Rubisco, but not regeneration capacity, was sensitive to high temperatures in low temperature grown plants. High growth temperatures appeared to affect the thermolability of the photosynthetic components of the two E. pauciflora provenances. Low temperature acclimation was similar for N. oleander and most of the Eucalyptus species and was accompanied by an increase in both biochemical parameters. Regeneration capacity was sensitive to low temperatures in high temperature grown E. miniata.

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Nikolic, B., D. Dodig, V. Jovanovic, V. Janjic et Sanja Djurovic. « Effects of temperature and light induction of CHL a fluorescence in situ : An ecophysiological view ». Archives of Biological Sciences 60, n^o 4 (2008) : 567–72. http://dx.doi.org/10.2298/abs0804567n.

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The effects of PAR and temperature on induction of Chl a fluorescence were observed on leaves of 20 plant species in their natural environments. Light affects the acceptor side of PS2. Temperature regulation of PS2 activity proceeds by affecting the RC and acceptor side of PS2. The impact of higher temperature can be attributed to greater fluidity of the thylakoid membranes. Photosynthetically active radiation and temperature under the given conditions are in highly significant positive correlation, so it is not clear whether this impact is due to individual or complementary mechanisms of PAR and/or temperature affecting photosynthetic processes in the thylakoid membranes. Also, it is not clear whether species specificity has any significance in the plant photosynthetic response to changes of PAR and temperature. Changes of PAR and temperature during induction of Chl a fluorescence do not affect Pindex, as a parameter of total photosynthesis.

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Mercado, L. M., J. Lloyd, A. J. Dolman, S. Sitch et S. Patiño. « Modelling basin-wide variations in Amazon forest productivity – Part 1 : Model calibration, evaluation and upscaling functions for canopy photosynthesis ». Biogeosciences Discussions 6, n^o 2 (11 mars 2009) : 2965–3030. http://dx.doi.org/10.5194/bgd-6-2965-2009.

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Abstract. Given the importance of Amazon rainforest in the global carbon and hydrological cycles, there is a need to parameterize and validate ecosystem gas exchange and vegetation models for this region in order to adequately simulate present and future carbon and water balances. In this study, a sun and shade canopy gas exchange model is calibrated and evaluated at five rainforest sites using eddy correlation measurements of carbon and energy fluxes. Results from the model-data evaluation suggest that with adequate parameterisation, photosynthesis models taking into account the separation of diffuse and direct irradiance and the dynamics of sunlit and shaded leaves can accurately represent photosynthesis in these forests. Also, stomatal conductance formulations that only take into account atmospheric demand fail to correctly simulate moisture and CO2 fluxes in forests with a pronounced dry season, particularly during afternoon conditions. Nevertheless, it is also the case that large uncertainties are associated not only with the eddy correlation data, but also with the estimates of ecosystem respiration required for model validation. To accurately simulate Gross Primary Productivity (GPP) and energy partitioning the most critical parameters and model processes are the quantum yield of photosynthetic uptake, the maximum carboxylation capacity of Rubisco, and simulation of stomatal conductance. Using this model-data synergy, we developed scaling functions to provide estimates of canopy photosynthetic parameters for a~range of diverse forests across the Amazon region, utilising the best fitted parameter for maximum carboxylation capacity of Rubisco, and foliar nutrients (N and P) for all sites.

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Mercado, L. M., J. Lloyd, A. J. Dolman, S. Sitch et S. Patiño. « Modelling basin-wide variations in Amazon forest productivity – Part 1 : Model calibration, evaluation and upscaling functions for canopy photosynthesis ». Biogeosciences 6, n^o 7 (28 juillet 2009) : 1247–72. http://dx.doi.org/10.5194/bg-6-1247-2009.

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Abstract. Given the importance of Amazon rainforest in the global carbon and hydrological cycles, there is a need to parameterize and validate ecosystem gas exchange and vegetation models for this region in order to adequately simulate present and future carbon and water balances. In this study, a sun and shade canopy gas exchange model is calibrated and evaluated at five rainforest sites using eddy correlation measurements of carbon and energy fluxes. Results from the model-data evaluation suggest that with adequate parameterisation, photosynthesis models taking into account the separation of diffuse and direct irradiance and the dynamics of sunlit and shaded leaves can accurately represent photosynthesis in these forests. Also, stomatal conductance formulations that only take into account atmospheric demand fail to correctly simulate moisture and CO2 fluxes in forests with a pronounced dry season, particularly during afternoon conditions. Nevertheless, it is also the case that large uncertainties are associated not only with the eddy correlation data, but also with the estimates of ecosystem respiration required for model validation. To accurately simulate Gross Primary Productivity (GPP) and energy partitioning the most critical parameters and model processes are the quantum yield of photosynthetic uptake, the maximum carboxylation capacity of Rubisco, and simulation of stomatal conductance. Using this model-data synergy, we developed scaling functions to provide estimates of canopy photosynthetic parameters for a range of diverse forests across the Amazon region, utilising the best fitted parameter for maximum carboxylation capacity of Rubisco, and foliar nutrients (N and P) for all sites.

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Huang, Meng-Yuan, Shau-Lian Wong et Jen-Hsien Weng. « Rapid Light-Response Curve of Chlorophyll Fluorescence in Terrestrial Plants : Relationship to CO2 Exchange among Five Woody and Four Fern Species Adapted to Different Light and Water Regimes ». Plants 10, n^o 3 (26 février 2021) : 445. http://dx.doi.org/10.3390/plants10030445.

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The rapid light response of electron transport rate (ETRR), obtained from chlorophyll fluorescence parameters by short illumination periods (10–30 s) at each light level, can provide a rapid and easy measurement of photosynthetic light response in plants. However, the relationship between ETRR and the steady-state light response of CO2 exchange rate (AS) of terrestrial plants has not been studied in detail. In this study, we compared the ETRR and AS for five woody and four fern species with different light and/or water adaptations. Under well-watered conditions, a constant temperature (25 °C) and with stomatal conductance (gs) not being a main limiting factor for photosynthesis, ETRR and AS were closely related, even when merging data for regression analysis for a species grown under different light conditions and measured under different light intensity and air humidity. However, when Alnus formosana was treated with low soil water and air humidity, because of the decrease in AS mainly due to stomatal closure, the ETRR–AS relation was not so close. In addition, at both 100 and 2000 μmol m−2 s−1 photosynthetic photon flux density (PPFD), ETRR and AS were significantly correlated within a plant group (i.e., woody plants and ferns) regardless of the broad difference in AS due to different species or environmental factors. The results indicate that the relationship between the ETRR and AS is varied by species. We concluded that 1) ETRR could reflect the variation in AS at each irradiance level within a species under well-watered conditions and 2) ETRR at 100 μmol m−2 s−1 PPFD (as the efficiency of light capture) or 2000 μmol m−2 s−1 PPFD (as a maximum photosynthetic parameter) could be used to compare the photosynthetic capacity within a plant group, such as woody plants and ferns.

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Wang, Xin, Wei Liu, Changpeng Xin, Yi Zheng, Yanbing Cheng, Su Sun, Runze Li et al. « Enhanced limonene production in cyanobacteria reveals photosynthesis limitations ». Proceedings of the National Academy of Sciences 113, n^o 50 (23 novembre 2016) : 14225–30. http://dx.doi.org/10.1073/pnas.1613340113.

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Terpenes are the major secondary metabolites produced by plants, and have diverse industrial applications as pharmaceuticals, fragrance, solvents, and biofuels. Cyanobacteria are equipped with efficient carbon fixation mechanism, and are ideal cell factories to produce various fuel and chemical products. Past efforts to produce terpenes in photosynthetic organisms have gained only limited success. Here we engineered the cyanobacterium Synechococcus elongatus PCC 7942 to efficiently produce limonene through modeling guided study. Computational modeling of limonene flux in response to photosynthetic output has revealed the downstream terpene synthase as a key metabolic flux-controlling node in the MEP (2-C-methyl-d-erythritol 4-phosphate) pathway-derived terpene biosynthesis. By enhancing the downstream limonene carbon sink, we achieved over 100-fold increase in limonene productivity, in contrast to the marginal increase achieved through stepwise metabolic engineering. The establishment of a strong limonene flux revealed potential synergy between photosynthate output and terpene biosynthesis, leading to enhanced carbon flux into the MEP pathway. Moreover, we show that enhanced limonene flux would lead to NADPH accumulation, and slow down photosynthesis electron flow. Fine-tuning ATP/NADPH toward terpene biosynthesis could be a key parameter to adapt photosynthesis to support biofuel/bioproduct production in cyanobacteria.

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Yang, Liu Qing, Fei Yong Liao et Kun Zhao. « Effect of Herbicides on the Photosynthetic Rate and Chlorophyll Fluorescence of Solidago canadensis L. » Advanced Materials Research 356-360 (octobre 2011) : 2785–90. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.2785.

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Solidago canadensis L. was treated with metsulfuron-methyl, fluroxypyr and iso-propyl glyphosate. The photosynthetic rate and chlorophyll fluorescence parameters were measured. The results showed that after treated 13 days later, the intrinsic conversion efficiency of light energy decreased, treatment A1B3 had the largest decline, which was 81.6 % of the control, the changes of treatments treated with iso-propyl glyphosate were not obvious; the photochemical quenching parameter of all treatments decreased, treatment A2B2 had the largest decline, which was 42.6 % of control; the photosynthetic electron transport rate decreased obviously, treatment A1B2，A1B3 and A2B2 had the largest decline, which was 20.0 % of control; the net photosynthetic rate decreased greatly, treatment A2B2 and A2B3 drooped more than others, which were 11.3% and 17.8% of control respectively. After treated 50 days later, the plants treated with metsulfuron-methyl and fluroxypyr were dead, whose net photosynthetic rates were zero. The net photosynthetic rates of the plants treated with iso-propyl glyphosate decreased to varying degrees, but plants were alive. Result shows that metsulfuron-methyl and fluroxypyr could be used to kill the Solidago canadensis L., the plants would be dead after treated 50 days later.

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Shevchenko, V. V., et O. Yu Bondarenko. « Spectral method of evaluation of photosynthetic apparatus thermal resistance ». Visnik ukrains'kogo tovaristva genetikiv i selekcioneriv 14, n^o 2 (31 décembre 2016) : 239–44. http://dx.doi.org/10.7124/visnyk.utgis.14.2.694.

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Aim. The aim of this work is to evaluate the possibilities of application of the spectral parameter - the relationship of the absorption values at wavelengths of 680 and 850 nm (k = A680 / A850) for testing heat resistance of plants to change the size of chloroplasts at short-term heating. Methods. The short-term (5 minutes) heating in the range 25-45oC was carried out for chloroplasts isolated from two-week-old pea, corn and 4 winter wheat varieties differing in heat resistance. From the absorption spectra of chloroplasts was calculated changes of parameter k. Results. All heated chloroplasts showed changes in the spectral parameter k. Particularly strong and stable changes observed during heating at 40-45 ° C. In terms of changes in the spectral parameter plants are ranged in the following order - corn, pea, wheat. Conclusions. The intensity of the k changes coincided with the preliminary estimation of thermal stability for corn and different varieties of winter wheat. It is recommended to use the spectral parameter k for the rapid screening of varieties on the thermal stability of the photosynthetic apparatus within the same species.Key words: chloroplasts of different species of plants, the photosynthetic apparatus, short-term heating, evaluation of the thermal stability.

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Živčák, M., K. Olšovská, P. Slamka, J. Galambošová, V. Rataj, Shao HB et M. Brestič. « Application of chlorophyll fluorescence performance indices to assess the wheat photosynthetic functions influenced by nitrogen deficiency ». Plant, Soil and Environment 60, No. 5 (7 mai 2014) : 210–15. http://dx.doi.org/10.17221/73/2014-pse.

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Nitrogen deficiency influences importantly the plant photosynthetic capacity and crop productivity. Here, we employed the rapid, non-invasive measurements of chlorophyll a fluorescence kinetics for calculation of the integrative fluorescence parameters related to the leaf photosynthetic performance. In pot experiments with winter wheat (Triticum aestivum L.) we cultivated plants during the whole growing period in the soil substrate supplied with four different doses of nitrogen. The leaf nitrogen and chlorophyll content as well as the plant dry mass were analyzed after chlorophyll fluorescence records in three growth stages. Our results indicate that the commonly used parameter Fv/Fm (the maximum quantum yield of photochemistry) was almost insensitive to nitrogen treatment. In contrary, the performance index (PIabs) and total performance index (PItot) were much more responsive and significant differences among plants of different nitrogen treatments as well as between the youngest and third leaf from the top were observed. Parameter PItot was shown to express only small diurnal changes, thus being more reliable and more useful for comparison of different samples in field conditions than more frequently used parameter PIabs.

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Silva-Pérez, Viridiana, Joanne De Faveri, Gemma Molero, David M. Deery, Anthony G. Condon, Matthew P. Reynolds, John R. Evans et Robert T. Furbank. « Genetic variation for photosynthetic capacity and efficiency in spring wheat ». Journal of Experimental Botany 71, n^o 7 (30 septembre 2019) : 2299–311. http://dx.doi.org/10.1093/jxb/erz439.

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Abstract One way to increase yield potential in wheat is screening for natural variation in photosynthesis. This study uses measured and modelled physiological parameters to explore genotypic diversity in photosynthetic capacity (Pc, Rubisco carboxylation capacity per unit leaf area at 25 °C) and efficiency (Peff, Pc per unit of leaf nitrogen) in wheat in relation to fertilizer, plant stage, and environment. Four experiments (Aus1, Aus2, Aus3, and Mex1) were carried out with diverse wheat collections to investigate genetic variation for Rubisco capacity (Vcmax25), electron transport rate (J), CO2 assimilation rate, stomatal conductance, and complementary plant functional traits: leaf nitrogen, leaf dry mass per unit area, and SPAD. Genotypes for Aus1 and Aus2 were grown in the glasshouse with two fertilizer levels. Genotypes for Aus3 and Mex1 experiments were grown in the field in Australia and Mexico, respectively. Results showed that Vcmax25 derived from gas exchange measurements is a robust parameter that does not depend on stomatal conductance and was positively correlated with Rubisco content measured in vitro. There was significant genotypic variation in most of the experiments for Pc and Peff. Heritability of Pc reached 0.7 and 0.9 for SPAD. Genotypic variation and heritability of traits show that there is scope for these traits to be used in pre-breeding programmes to improve photosynthesis with the ultimate objective of raising yield potential.

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Šajbidorová, Viera, Helena Lichtnerová et Viera Paganová. « The Impact of Different Water Regime on Chlorophyll Fluorescence of Pyrus pyraster L. and Sorbus domestica L ». Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 63, n^o 5 (2015) : 1575–79. http://dx.doi.org/10.11118/actaun201563051575.

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The water deficit is considered to be significant cause of photosynthesis defects. Measuring of chlorophyll fluorescence is one of the methods revealing defects in the photosynthetic apparatus. The experiment was established with two woody plant (Pyrus pyraster L. and Sorbus domestica L.) cultivated in two different regimes of the substrate saturation. The measurement of the modulated fluorescence of chlorophyll a was done by FMS1 fluorometer during three-week period between June and September (2012 and 2013). There were analysed selected parameters of chlorophyll fluorescence: Fv/Fm – maximum quantum efficiency of PSII, ΦPSII – effective quantum yield of PSII and RFD – chlorophyll fluorescence decrease ratio. According to the obtained results, Pyrus pyraster has probably higher potential for adaptation to water deficiency. There were recorded the significant decreases mainly in the values of parameter RFD and ΦPSII for Sorbus domestica within duration of experiment with different water regime in both growing seasons 2012 and 2013. The results document a weak sensitivity of the parameter Fv/Fm on changes in the amount of available water in the substrate in both taxa.

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Walker, Anthony P., Ming Ye, Dan Lu, Martin G. De Kauwe, Lianhong Gu, Belinda E. Medlyn, Alistair Rogers et Shawn P. Serbin. « The multi-assumption architecture and testbed (MAAT v1.0) : R code for generating ensembles with dynamic model structure and analysis of epistemic uncertainty from multiple sources ». Geoscientific Model Development 11, n^o 8 (10 août 2018) : 3159–85. http://dx.doi.org/10.5194/gmd-11-3159-2018.

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Abstract. Computer models are ubiquitous tools used to represent systems across many scientific and engineering domains. For any given system, many computer models exist, each built on different assumptions and demonstrating variability in the ways in which these systems can be represented. This variability is known as epistemic uncertainty, i.e. uncertainty in our knowledge of how these systems operate. Two primary sources of epistemic uncertainty are (1) uncertain parameter values and (2) uncertain mathematical representations of the processes that comprise the system. Many formal methods exist to analyse parameter-based epistemic uncertainty, while process-representation-based epistemic uncertainty is often analysed post hoc, incompletely, informally, or is ignored. In this model description paper we present the multi-assumption architecture and testbed (MAAT v1.0) designed to formally and completely analyse process-representation-based epistemic uncertainty. MAAT is a modular modelling code that can simply and efficiently vary model structure (process representation), allowing for the generation and running of large model ensembles that vary in process representation, parameters, parameter values, and environmental conditions during a single execution of the code. MAAT v1.0 approaches epistemic uncertainty through sensitivity analysis, assigning variability in model output to processes (process representation and parameters) or to individual parameters. In this model description paper we describe MAAT and, by using a simple groundwater model example, verify that the sensitivity analysis algorithms have been correctly implemented. The main system model currently coded in MAAT is a unified, leaf-scale enzyme kinetic model of C3 photosynthesis. In the Appendix we describe the photosynthesis model and the unification of multiple representations of photosynthetic processes. The numerical solution to leaf-scale photosynthesis is verified and examples of process variability in temperature response functions are provided. For rapid application to new systems, the MAAT algorithms for efficient variation of model structure and sensitivity analysis are agnostic of the specific system model employed. Therefore MAAT provides a tool for the development of novel or toy models in many domains, i.e. not only photosynthesis, facilitating rapid informal and formal comparison of alternative modelling approaches.

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Wang, H. B., M. G. Ma, Y. M. Xie, X. F. Wang et J. Wang. « Parameter inversion estimation in photosynthetic models : Impact of different simulation methods ». Photosynthetica 52, n^o 2 (1 juin 2014) : 233–46. http://dx.doi.org/10.1007/s11099-014-0027-8.

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Széles, Eszter, Krisztina Nagy, Ágnes Ábrahám, Sándor Kovács, Anna Podmaniczki, Valéria Nagy, László Kovács, Péter Galajda et Szilvia Z. Tóth. « Microfluidic Platforms Designed for Morphological and Photosynthetic Investigations of Chlamydomonas reinhardtii on a Single-Cell Level ». Cells 11, n^o 2 (14 janvier 2022) : 285. http://dx.doi.org/10.3390/cells11020285.

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Chlamydomonas reinhardtii is a model organism of increasing biotechnological importance, yet, the evaluation of its life cycle processes and photosynthesis on a single-cell level is largely unresolved. To facilitate the study of the relationship between morphology and photochemistry, we established microfluidics in combination with chlorophyll a fluorescence induction measurements. We developed two types of microfluidic platforms for single-cell investigations: (i) The traps of the “Tulip” device are suitable for capturing and immobilizing single cells, enabling the assessment of their photosynthesis for several hours without binding to a solid support surface. Using this “Tulip” platform, we performed high-quality non-photochemical quenching measurements and confirmed our earlier results on bulk cultures that non-photochemical quenching is higher in ascorbate-deficient mutants (Crvtc2-1) than in the wild-type. (ii) The traps of the “Pot” device were designed for capturing single cells and allowing the growth of the daughter cells within the traps. Using our most performant “Pot” device, we could demonstrate that the FV/FM parameter, an indicator of photosynthetic efficiency, varies considerably during the cell cycle. Our microfluidic devices, therefore, represent versatile platforms for the simultaneous morphological and photosynthetic investigations of C. reinhardtii on a single-cell level.

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Schroeter, B., L. Kappen et C. Moldaenke. « Continuous in Situ Recording of the Photosynthetic Activity of Antarctic Lichens—established Methods and a New Approach ». Lichenologist 23, n^o 3 (juillet 1991) : 253–65. http://dx.doi.org/10.1017/s0024282991000415.

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AbstractA new method is described that records the periods of photosynthetic and respiratory activity in lichen thalli in situ by measuring the actinic chlorophyll fluorescence response of the photobiont. The technique is based on a pulse amplitude modulation fluorometer that was specially developed for continuous and unattended measurements in the Antarctic. In Livingston Island, South Shetland Islands, the periods of metabolic activity of Usnea antarctica were recorded simultaneously with the microclimatic parameter in its natural environment. In one series of diurnal measurements the fluorescence response signal was treated as a qualitative on/off signal for photosynthetic activity. In a parallel series the diurnal courses of net photosynthesis and dark respiration of rain-moistened thalli of U. antarctica were measured by means of a CO2/H2O porometer together with gravimetric water content determination. Both methods showed marked coincidence from low water content to water saturation of the thalli. In the laboratory both the actinic fluorescence response and the photosynthetic rate as a function of thallus water content were investigated in Caloplaca regalis. In the laboratory experiments the CO2 exchange cuvette contained a balance for gravimetric water content control as well as the glass-fibre optics of the fluorescence analysis equipment. The experiments revealed a quantitative relationship between actinic fluorescence and photosynthetic rate within the range of optimum to limiting low thallus water content. The method described is suitable for measurements of lichen activity in field microclimate studies and should allow continuous unattended year-round measurements of lichen activity, which are needed in remote regions such as Antarctica.

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Schutze, Inana X., Pedro T. Yamamoto, José B. Malaquias, Matthew Herritt, Alison Thompson, Paul Merten et Steve E. Naranjo. « Correlation-Based Network Analysis of the Influence of Bemisia tabaci Feeding on Photosynthesis and Foliar Sugar and Starch Composition in Soybean ». Insects 13, n^o 1 (5 janvier 2022) : 56. http://dx.doi.org/10.3390/insects13010056.

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Bemisia tabaci (MEAM1) represents a species of economic importance in soybean. One of the obstacles to the management of B. tabaci is the quantification of damage by the pest because damage is indirectly inferred through losses in productivity. The objective of this study was to characterize the influence of B. tabaci feeding on soybean by assessing effects on photosynthetic parameters and the sugar and starch content of soybean leaves. The goal was to identify the optimal parameter to directly quantify pest damage on crop yield. Correlation networks were created among data on sugar content (fructose, glucose, and sucrose), starch and photosynthetic parameters (initial fluorescence, performance index on absorption basis, and turn-over number), and the number of nymphs at each of three infestations level (low, medium, and high) during both the vegetative and reproductive stage of the crop. In general, nymphs were more abundant during the vegetative stage. Starch content was strongly correlated with nymph density. A strong positive correlation was observed between fructose and nymph density during the vegetative stage. Among the photosynthetic parameters, the turn-over number N was positively correlated with nymph density at a low-infestation level and negatively correlated with nymphs when they occurred at a high-infestation level. B. tabaci feeding affected the plant’s physiology and its interaction is reflected in part by the relationships among photosynthetic parameters as well as the levels of sugars and starch. This understanding might be useful in developing better monitoring tools for pest management.

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Dutta, Debsunder, David S. Schimel, Ying Sun, Christiaan van der Tol et Christian Frankenberg. « Optimal inverse estimation of ecosystem parameters from observations of carbon and energy fluxes ». Biogeosciences 16, n^o 1 (11 janvier 2019) : 77–103. http://dx.doi.org/10.5194/bg-16-77-2019.

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Abstract. Canopy structural and leaf photosynthesis parameterizations such as maximum carboxylation capacity (Vcmax), slope of the Ball–Berry stomatal conductance model (BBslope) and leaf area index (LAI) are crucial for modeling plant physiological processes and canopy radiative transfer. These parameters are large sources of uncertainty in predictions of carbon and water fluxes. In this study, we develop an optimal moving window nonlinear Bayesian inversion framework to use the Soil Canopy Observation Photochemistry and Energy fluxes (SCOPE) model for constraining Vcmax, BBslope and LAI with observations of coupled carbon and energy fluxes and spectral reflectance from satellites. We adapted SCOPE to follow the biochemical implementation of the Community Land Model and applied the inversion framework for parameter retrievals of plant species that have both the C3 and C4 photosynthetic pathways across three ecosystems. We present comparative analysis of parameter retrievals using observations of (i) gross primary productivity (GPP) and latent energy (LE) fluxes and (ii) improvement in results when using flux observations along with reflectance. Our results demonstrate the applicability of the approach in terms of capturing the seasonal variability and posterior error reduction (40 %–90 %) of key ecosystem parameters. The optimized parameters capture the diurnal and seasonal variability in the GPP and LE fluxes well when compared to flux tower observations (0.95>R2>0.79). This study thus demonstrates the feasibility of parameter inversions using SCOPE, which can be easily adapted to incorporate additional data sources such as spectrally resolved reflectance and fluorescence and thermal emissions.

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Giossi, Chiara, Paulo Cartaxana et Sónia Cruz. « Photoprotective Role of Neoxanthin in Plants and Algae ». Molecules 25, n^o 20 (11 octobre 2020) : 4617. http://dx.doi.org/10.3390/molecules25204617.

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Light is a paramount parameter driving photosynthesis. However, excessive irradiance leads to the formation of reactive oxygen species that cause cell damage and hamper the growth of photosynthetic organisms. Xanthophylls are key pigments involved in the photoprotective response of plants and algae to excessive light. Of particular relevance is the operation of xanthophyll cycles (XC) leading to the formation of de-epoxidized molecules with energy dissipating capacities. Neoxanthin, found in plants and algae in two different isomeric forms, is involved in the light stress response at different levels. This xanthophyll is not directly involved in XCs and the molecular mechanisms behind its photoprotective activity are yet to be fully resolved. This review comprehensively addresses the photoprotective role of 9′-cis-neoxanthin, the most abundant neoxanthin isomer, and one of the major xanthophyll components in plants’ photosystems. The light-dependent accumulation of all-trans-neoxanthin in photosynthetic cells was identified exclusively in algae of the order Bryopsidales (Chlorophyta), that lack a functional XC. A putative photoprotective model involving all-trans-neoxanthin is discussed.

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Bauerle, William L., G. Geoff Wang, Nilakantan S. Rajaraman et Shruthi Anantharamu. « The Implications of Temperature and Mesophyll Response Functions in a Biochemically-based Model of Photosynthesis : Effects on Whole Crown Carbon Exchange Estimates ». HortScience 40, n^o 4 (juillet 2005) : 1145C—1145. http://dx.doi.org/10.21273/hortsci.40.4.1145c.

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The estimate of the photosynthetic response to temperature is important for accurate growth predictions in process-based models designed to respond to broad variation in environmental conditions. Several studies have attempted to decipher the temperature and mesophyll response functions for use in the widely used Farquhar et al. (1980) biochemically based photosynthesis model. Unfortunately, published values of Rubisco kinetic properties (Kc and Ko) differ among species. To compound the problem, the methodology used to estimate Kc and Ko has not been consistent. We compared the variation in carbon gain estimates of a whole tree by incorporating the different temperature parameter estimates of Bernacchi et al. (2001, 2003) and Medlyn et al. (2002) into a three-dimensional biological process-based model. In addition, we also investigated the contribution of mesophyll conductance by incorporating Rubisco enzyme kinetics parameters reported by Bernacchi et al. (2002). Temperature parameters substantially influenced our whole tree carbon gain estimates. The variation among model estimates of aboveground net carbon gain was ≈11% for 3-year-old red maple saplings. Variation was even greater when mesophyll conductance was incorporated. The different parameter estimates, if not validated at the whole plant scale, can introduce inaccuracies and exacerbate carbon gain estimates of single plants, stands of plants, and entire ecosystems.

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HU, S., et X. MO. « Prediction of crop productivity and evapotranspiration with two photosynthetic parameter regionalization methods ». Journal of Agricultural Science 152, n^o 1 (27 novembre 2012) : 119–33. http://dx.doi.org/10.1017/s0021859612000901.

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SUMMARYParameter regionalization is the foundation for the spatial application of an ecosystem model at the canopy level and has been improved greatly by remote sensing (RS). Photosynthetic rate is restricted by the carboxylation rate, which is limited by the activity of the enzyme Rubisco. By including RS normalized difference vegetation index (NDVI) and census data of grain yield at the county level in an ecosystem model (vegetation interface processes (VIP) model), the pattern of photosynthetic parameter Vcmax (maximum catalytic activity of Rubisco) of winter wheat was obtained and then used to simulate the wheat yield and evapotranspiration (ET) in the North China Plain (referred to as the Vcmax method). To evaluate its performance, the simulated yield and ET were compared with those derived by the leaf area index (LAI) method using the retrieved LAI from NDVI to drive the VIP model. The results showed that the Vcmax method performed better than the LAI method in highly productive fields, while the LAI method described the inter-annual variations of yield more favourably in fields with low productivity. Over the study area, average yield (4520 kg/ha) and seasonal ET (360 mm) simulated by the LAI method was slightly lower than those simulated using the Vcmax method (4730 kg/ha for yield and 372 mm for ET). Compared with the census data of yield, the relative root mean square error (RMSE) of grain yield with Vcmax method (0·17) was lower than that of the LAI method (0·20). In conclusion, the physical model with spatial Vcmax pattern from remote sensing is reliable for regional crop productivity prediction.

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Michel-Rodriguez, Monica, Sebastien Lefebvre, Muriel Crouvoisier, Xavier Mériaux et Fabrice Lizon. « Underwater light climate and wavelength dependence of microalgae photosynthetic parameters in a temperate sea ». PeerJ 9 (4 octobre 2021) : e12101. http://dx.doi.org/10.7717/peerj.12101.

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Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and quality of underwater light (i.e. light climate) is essential to understand primary production. A wavelength-dependent photoacclimation strategy was assessed using a multi-color pulse-amplitude-modulation chlorophyll fluorometer for phytoplankton samples collected in the spring at 19 locations across the English Channel. The functional absorption cross section of photosystem II, photosynthetic electron transport (PETλ) parameters and non-photochemical quenching were analyzed using an original approach with a sequence of three statistical analyses. Linear mixed-effects models using wavelength as a longitudinal variable were first applied to distinguish the fixed effect of the population from the random effect of individuals. Population and individual trends of wavelength-dependent PETλ parameters were consistent with photosynthesis and photoacclimation theories. The natural phytoplankton communities studied were in a photoprotective state for blue wavelengths (440 and 480 nm), but not for other wavelengths (green (540 nm), amber (590 nm) and light red (625 nm)). Population-detrended PETλ values were then used in multivariate analyses (partial triadic analysis and redundancy analysis) to study ecological implications of PETλ dynamics among water masses. Two wavelength ratios based on the microalgae saturation parameter Ek (in relative and absolute units), related to the hydrodynamic regime and underwater light climate, clearly confirmed the physiological state of microalgae. They also illustrate more accurately that natural phytoplankton communities can implement photoacclimation processes that are influenced by in situ light quality during the daylight cycle in temporarily and weakly stratified water. Ecological implications and consequences of PETλ are discussed in the context of turbulent coastal ecosystems.

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Filaček, Andrej, Marek Živčák, Lorenzo Ferroni, Mária Barboričová, Kristína Gašparovič, Xinghong Yang, Marco Landi et Marián Brestič. « Pre-Acclimation to Elevated Temperature Stabilizes the Activity of Photosystem I in Wheat Plants Exposed to an Episode of Severe Heat Stress ». Plants 11, n^o 5 (24 février 2022) : 616. http://dx.doi.org/10.3390/plants11050616.

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The importance of high temperature as an environmental factor is growing in proportion to deepening global climate change. The study aims to evaluate the effects of long-term acclimation of plants to elevated temperature on the tolerance of their photosynthetic apparatus to heat stress. Three wheat (Triticum sp. L.) genotypes differing in leaf and photosynthetic traits were analyzed: Thesee, Roter Samtiger Kolbenweizen, and ANK 32A. The pot experiment was established in natural conditions outdoors (non-acclimated variant), from which a part of the plants was placed in foil tunnel with elevated temperature for 14 days (high temperature-acclimated variant). A severe heat stress screening experiment was induced by an exposition of the plans in a growth chamber with artificial light and air temperature up to 45 °C for ~12 h before the measurements. The measurements of leaf photosynthetic CO2 assimilation, stomatal conductance, and rapid kinetics of chlorophyll a fluorescence was performed. The results confirmed that a high temperature drastically reduced the photosynthetic assimilation rate caused by the non-stomatal (biochemical) limitation of photosynthetic processes. On the other hand, the chlorophyll fluorescence indicated only a moderate level of decrease of quantum efficiency of photosystem (PS) II (Fv/Fm parameter), indicating mostly reversible heat stress effects. The heat stress led to a decrease in the number of active PS II reaction centers (RC/ABS) and overall activity o PSII (PIabs) in all genotypes, whereas the PS I (parameter ψREo) was negatively influenced by heat stress in the non-acclimated variant only. Our results showed that the genotypes differ in acclimation capacity to heat stress, and rapid noninvasive techniques may help screen the stress effects and identify more tolerant crop genotypes. The acclimation was demonstrated more at the PS I level, which may be associated with the upregulation of alternative photosynthetic electron transport pathways with clearly protective functions.

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Kovalyova, I. V. « Quantitative relationship between solar radiation intensity and average daily value of photosynthesis light saturation for phytoplankton in the deep-water area of the Black Sea ». Marine Biological Journal 5, n^o 1 (31 mars 2020) : 43–49. http://dx.doi.org/10.21072/mbj.2020.05.1.05.

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According to data obtained during expeditions in the Black Sea (1987–1993), linear relationship between the light flux density incident on the sea surface (E0) and the starting point of photosynthesis light saturation (En opt) is revealed. For calculations, measurements of phytoplankton photosynthesis rate obtained by the radiocarbon method were used. The equation of the relationship between the values reported is presented for the first time for the Black Sea. En opt is the average daily, optimal value of photosynthesis light saturation. The parameters of photosynthesis – light curve, determined in short-period exposures under constant illumination, differ from the parameters obtained in long-term experiments under conditions of variable illumination. This is due to different effects of the intensity and dose on the phytoplankton photosynthesis rate. The values of photosynthetic parameters for a certain time are integrated into a single value which is the optimum for the entire period observed. The approximation of daily data integrated is carried out both separately for seasons and in general for the period of 1987–1993. Using statistical processing of data of average daily values of the intensity of solar radiation incident on the sea surface, slope of the photosynthesis – light curve, and maximum photosynthesis rate, the approximation is determined for the functional dependence of En opt on E0. The equation is applicable in the range of light intensity 3 to 75 mol quanta·m−2·day−1. It describes with high reliability a change of average daily value of photosynthesis light saturation in the Black Sea during different seasons of the year. The equation includes a parameter easily accessible for measurement. It can be used in analysis of physiological characteristics of phytoplankton and calculation of integrated phytoplankton productivity in euphotic layer with using both satellite and expedition data.

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Кулешова, Т. Э., Е. С. Павлова et Н. Р. Галль. « Фракционирование изотопов углерода -=SUP=-13-=/SUP=-С/-=SUP=-12-=/SUP=-С из углекислого газа атмосферы в продукты фотосинтеза в листьях растений в зависимости от спектральных характеристик световой среды ». Письма в журнал технической физики 46, n^o 16 (2020) : 19. http://dx.doi.org/10.21883/pjtf.2020.16.49848.18333.

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We have studied influence of the light with various spectral characteristics, coming to plants during its growth, on the distribution of carbon isotopes between atmospheric carbon dioxide and the primary products of photosynthesis in plant leaves, using the developed set of methods and laboratory setups. The difference between the carbon isotopic composition in the air near the plants and in their leaves varies from 7 to 19 ‰, increase in the red component of the spectrum resulting in leave enrichment with light carbon isotope 12C. This difference reflects the degree of isotope fractionation during the plant life, characterizes the rate of carbon assimilation due to photosynthetic reactions, and can be used as a phytomonitoring parameter.

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Abakumov, A. I., et S. Ya Pak. « Modeling of Photosynthesis Process and Assessing Of Phytoplankton Dynamics Based On Droop Model ». Mathematical Biology and Bioinformatics 16, n^o 2 (27 octobre 2021) : 380–93. http://dx.doi.org/10.17537/2021.16.380.

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Droop's well-known model simulates phytoplankton biomass dynamics based on nutrient limitation. The defining parameter is the nutrient concentration in phytoplankton cells (cell quota). This model is modified to description of the photosynthesis processes. The effects of photosynthetically active radiation must be taken into account. At the same time, the nutritional factor remains the main one. Water temperature is considered as a controlling factor. The influence of light during photosynthesis plays a decisive role. The decisive factor is the presence of photosynthetic substances. We conventionally combine them under the name "chlorophyll". Sufficient variability in the proportion of chlorophyll in phytoplankton (chlorophyll quota) directly affects biomass production. The equation for the dynamics of chlorophyll quota is added to the Droop model. The parameters of the model depend on the concentration of nutrients, illumination and water temperature. The properties of the solutions in the model are investigated, the conditions for the existence and stability of equilibrium solutions are clarified. Complex dynamic regimes are revealed in the case of unstable equilibria. It was found that the most sensitive parameter for biomass dynamics is the minimum value of the cell quota. The dynamics of indicators for the daily cycle and the annual cycle of seasonal changes are calculated. The influence of nutrition, illumination and temperature on biomass production has been clarified. During the day, the chlorophyll quota fluctuates insignificantly due to a short period of time. The changes are noticeable at longer times for example during the season.

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Zielińska, Elżbieta, Krystyna Matusiak-Mikulin, Krzysztof Grabski, Anna Heda, Aleksandra Krzykowska et Zbigniew Tukaj. « Growth Improvement of Nicotiana and Arabidopsis In Vitro by Microalgal Conditioned Media ». Acta Biologica Cracoviensia s. Botanica 56, n^o 2 (1 mars 2015) : 91–97. http://dx.doi.org/10.2478/abcsb-2014-0029.

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Abstract Conditioned medium (CM) is a general term describing media in which cells have already been cultivated for some time. Such media, usually clarified by filtration, have been used by plant biotechnologists as additives sup-porting the growth of cell suspensions, organs and whole plants. This study examined the effect of CM obtained from green alga Desmodesmus subspicatus on the growth and functioning of the photosynthetic apparatus of Nicotiana tabacum and Arabidopsis thaliana in culture in vitro. Plants where cultured on CM diluted 1.25-, 2-and 5-fold with MS medium. The increase in fresh and dry weight was highest in tobacco and Arabidopsis cultured on CM/2 and CM/1.25 media. Those two concentrations also increased the amount of chlorophylls in both plants tested. CM improved parameter PI (reflecting the photosynthetic “vitality” of the organism) and electron transport efficiency, and increased the fraction of active reaction centers. Analysis of chlorophyll fluorescence in vivo suggests that the improvement of these plants grown in the presence of algal CM may result from stimulation of photosynthesis. Algal CM offers a convenient, cheap, universal supplement for stimulating the growth of higher plants in vitro.

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Djukic, Nevena, Stefan Markovic, Jasna Mastilovic et Predrag Simovic. « Differences in proline accumulation between wheat varieties in response to heat stress ». Botanica Serbica 45, n^o 1 (2021) : 61–69. http://dx.doi.org/10.2298/botserb2101061d.

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Proline is one of the organic osmolytes that accumulates in plants in response to stressful environmental conditions. The aim of this study was to determine the concentration of proline in the grain filling phase in ten winter wheat cultivars under conditions of prolonged periods of air temperatures above 30?C and to assess the variability of wheat variety responses. The correlation between proline accumulation and photosynthetic pigments, accumulated starch and yield was also determined. In the experimental field, flag leaves were sampled for each variety in the grain filling phase. Statistical data analysis and parameter correlation were performed using the SPSS program. The results showed that there is a statistically significant difference between proline values in moderate and high air temperature conditions when proline accumulation occurs. The significant correlation of accumulated starch content and yield with proline concentration showed that in addition to higher proline values under heat stress, wheat varieties Apac, Talas and Futura also have higher yield and starch content. A correlation was also found between proline concentration and photosynthetic pigment contents, where the Apac wheat variety showed the best adaptive response to the investigated traits and was characterized by a smaller reduction in photosynthetic pigment content under heat stress. The interrelation of proline with the photosynthetic pigment content and wheat quality parameters may be important in breeding technologies aimed at improving wheat stress tolerance.

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Lina, herlina, widianarko Budi et rya sunoko Henna. « Phytoremediation of Lead Contaminated Soils using Cordyline fruicosa (L) ». E3S Web of Conferences 73 (2018) : 05023. http://dx.doi.org/10.1051/e3sconf/20187305023.

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Phytoremediation is an eco-friendly and low cost potential strategy for cleaning up of heavy metals from contaminated soils. Selection of promising plant is an important approach for successful phytoremediation. In this study the role of Cordyline fruicosa (L ) plants as a potential phytoremediator to soils contaminated with lead (Pb) was investigated. Pot culture experiments using Cordyline fruicosa (L ) with different level of lead 250, 500 and 750 mg Pb kg-1 soil. The growth parameter biomass root and leaf, Pb accumulation in plant and photosynthetic pigment content were measured after 40 days. The results showed that the increase lead concentrations caused a reduction in most growth parameter and photosynthetic pigment content. On the other hand the lead accumulation in root and leaf was increased by increasing lead concentrations.

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Donahue, Raymon A., Tim D. Davis, Charles H. Michler, Don E. Riemenschneider, Doug R. Carter, Paula E. Marquardt, Narendra Sankhla, Daksha Sankhla, Bruce E. Haissig et J. G. Isebrands. « Growth, photosynthesis, and herbicide tolerance of genetically modified hybrid poplar ». Canadian Journal of Forest Research 24, n^o 12 (1 décembre 1994) : 2377–83. http://dx.doi.org/10.1139/x94-306.

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Hybrid poplar clone NC–5339 (Populusalba × Populusgrandidentata cv. Crandon) was genetically modified for glyphosate (N-(phosphonomethyl)glycine) tolerance by Agrobacterium-mediated transformation with genetic constructs (pPMG 85/587 and pCGN 1107) that included the mutant aroA gene for 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase (EC 2.5.1.19) and the neomycin phosphotransferase selectable marker gene. pCGN 1107 also harbored the coding sequence for a chloroplast transit peptide and the CaMV 35S promoter fused to the mutant aroA gene. Transformants were selected for kanamycin tolerance, and integration of the aroA gene was verified by Southern blot analysis. Cuttings of NC-5339 and the derived transformants were rooted and grown in glasshouses at separate locations, with maximum photosynthetic photon flux density of 1600 and 750 μmol•m−2•s−1. Productivity was assessed by growth studies and photosynthesis measurements at both locations. Glyphosate tolerance was tested by (i) measurement of chlorophyll concentration in herbicide-treated leaf discs and (ii) whole-plant spray tests. Plants transformed with construct pCGN 1107 were the most herbicide tolerant. Perhaps high-level expression of the aroA gene by the CaMV 35S promoter, transport of mutant EPSP synthase into the chloroplasts, or both facilitated glyphosate tolerance. Plants grown at higher photosynthetic photon flux densities (1600 vs. 750 μmol•m−2•s−1) had significantly higher maximum net photosynthesis (19.8 vs. 16.2 μmol•m−2•s−1) and more biomass accumulation (47.6 vs. 33.7 g). However, there were no significant differences between NC-5339 and transformants within location for net photosynthesis or any growth parameter. Genetic modification of hybrid poplar NC-5339 for glyphosate tolerance did not adversely affect plant productivity at either location.

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