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1
Bai, Yuyu, e John F. Kelly. "A Study of Photosynthetic Activities of Eight Asparagus Genotypes under Field Conditions". Journal of the American Society for Horticultural Science 124, n. 1 (gennaio 1999): 61–66. http://dx.doi.org/10.21273/jashs.124.1.61.
Testo completoAbstract (sommario):
Net photosynthesis from whole plants of eight asparagus (Asparagus officinalis L.) genotypes was measured at two locations in an open infrared gas analysis system. Measurements started at about the completion of full fern growth, which occurred at the end of July and lasted through the season until fern senescence in late September. Net photosynthesis of the eight genotypes ranged from 15.67 to 27.79 μmol·m-2·s-1. Significant differences (P < 0.1) in net photosynthesis were found among the eight genotypes. Both yield and specific leaf mass (SLM) were correlated significantly with net photosynthesis. We suggest that specific leaf mass can be used as a criterion for selecting genotype of high photosynthetic ability. Daily photosynthetic rate patterns were studied and appear to be related to daily changes of stomatal conductance. Seasonal changes of asparagus' photosynthetic activity were studied. High photosynthetic activity was observed from July through August. Photosynthetic activity decreased greatly in September along with the fern maturation and unfavorable changes in environmental conditions.
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Capó-Bauçà, Sebastià, Marcel Font-Carrascosa, Miquel Ribas-Carbó, Andrej Pavlovič e Jeroni Galmés. "Biochemical and mesophyll diffusional limits to photosynthesis are determined by prey and root nutrient uptake in the carnivorous pitcher plant Nepenthes × ventrata". Annals of Botany 126, n. 1 (16 marzo 2020): 25–37. http://dx.doi.org/10.1093/aob/mcaa041.
Testo completoAbstract (sommario):
Abstract Background and Aims Carnivorous plants can enhance photosynthetic efficiency in response to prey nutrient uptake, but the underlying mechanisms of increased photosynthesis are largely unknown. Here we investigated photosynthesis in the pitcher plant Nepenthes × ventrata in response to different prey-derived and root mineral nutrition to reveal photosynthetic constrains. Methods Nutrient-stressed plants were irrigated with full inorganic solution or fed with four different insects: wasps, ants, beetles or flies. Full dissection of photosynthetic traits was achieved by means of gas exchange, chlorophyll fluorescence and immunodetection of photosynthesis-related proteins. Leaf biochemical and anatomical parameters together with mineral composition, nitrogen and carbon isotopic discrimination of leaves and insects were also analysed. Key Results Mesophyll diffusion was the major photosynthetic limitation for nutrient-stressed Nepenthes × ventrata, while biochemistry was the major photosynthetic limitation after nutrient application. The better nutrient status of insect-fed and root-fertilized treatments increased chlorophyll, pigment–protein complexes and Rubisco content. As a result, both photochemical and carboxylation potential were enhanced, increasing carbon assimilation. Different nutrient application affected growth, and root-fertilized treatment led to the investment of more biomass in leaves instead of pitchers. Conclusions The study resolved a 35-year-old hypothesis that carnivorous plants increase photosynthetic assimilation via the investment of prey-derived nitrogen in the photosynthetic apparatus. The equilibrium between biochemical and mesophyll limitations of photosynthesis is strongly affected by the nutrient treatment.
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Zhu, Xin-Guang, Donald R. Ort, Martin A. J. Parry e Susanne von Caemmerer. "A wish list for synthetic biology in photosynthesis research". Journal of Experimental Botany 71, n. 7 (15 febbraio 2020): 2219–25. http://dx.doi.org/10.1093/jxb/eraa075.
Testo completoAbstract (sommario):
Abstract This perspective summarizes the presentations and discussions at the ‘ International Symposium on Synthetic Biology in Photosynthesis Research’, which was held in Shanghai in 2018. Leveraging the current advanced understanding of photosynthetic systems, the symposium brain-stormed about the redesign and engineering of photosynthetic systems for translational goals and evaluated available new technologies/tools for synthetic biology as well as technological obstacles and new tools that would be needed to overcome them. Four major research areas for redesigning photosynthesis were identified: (i) mining natural variations of photosynthesis; (ii) coordinating photosynthesis with pathways utilizing photosynthate; (iii) reconstruction of highly efficient photosynthetic systems in non-host species; and (iv) development of new photosynthetic systems that do not exist in nature. To expedite photosynthesis synthetic biology research, an array of new technologies and community resources need to be developed, which include expanded modelling capacities, molecular engineering toolboxes, model species, and phenotyping tools.
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Gautam, Harsha, Zebus Sehar, Md Tabish Rehman, Afzal Hussain, Mohamed F. AlAjmi e Nafees A. Khan. "Nitric Oxide Enhances Photosynthetic Nitrogen and Sulfur-Use Efficiency and Activity of Ascorbate-Glutathione Cycle to Reduce High Temperature Stress-Induced Oxidative Stress in Rice (Oryza sativa L.) Plants". Biomolecules 11, n. 2 (18 febbraio 2021): 305. http://dx.doi.org/10.3390/biom11020305.
Testo completoAbstract (sommario):
The effects of nitric oxide (NO) as 100 µM sodium nitroprusside (SNP, NO donor) on photosynthetic-nitrogen use efficiency (NUE), photosynthetic-sulfur use efficiency (SUE), photosynthesis, growth and agronomic traits of rice (Oryza sativa L.) cultivars, Taipie-309 (high photosynthetic-N and SUE) and Rasi (low photosynthetic-N and SUE) were investigated under high temperature stress (40 °C for 6 h). Plants exposed to high temperature stress caused significant reduction in photosynthetic activity, use efficiency of N and S, and increment in H2O2 and thiobarbituric acid reactive substance (TBARS) content. The drastic effects of high temperature stress were more pronounced in cultivar Rasi than Taipie-309. However, foliar spray of SNP decreased the high temperature induced H2O2 and TBARS content and increased accumulation of proline and activity of ascorbate–glutathione cycle that collectively improved tolerance to high temperature stress more effectively in Taipie-309. Exogenously applied SNP alleviated the high temperature induced decrease in photosynthesis through maintaining higher photosynthetic-NUE and photosynthetic-SUE, activity of ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco), and synthesis of reduced glutathione (GSH). The use of 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (cPTIO, NO scavenger) substantiated the study that in the absence of NO oxidative stress increased, while NO increased photosynthetic-NUE and photosynthetic-SUE, net photosynthesis and plant dry mass. Taken together, the present investigation reveals that NO increased heat stress tolerance and minimized high temperature stress adversaries more effectively in cultivar Taipie-309 than Rasi by enhancing photosynthetic-NUE and SUE and strengthening the antioxidant defense system.
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Man, Rongzhou, e Victor J. Lieffers. "Seasonal variations of photosynthetic capacities of white spruce (Picea glauca) and jack pine (Pinus banksiana) saplings". Canadian Journal of Botany 75, n. 10 (1 ottobre 1997): 1766–71. http://dx.doi.org/10.1139/b97-890.
Testo completoAbstract (sommario):
Seasonal photosynthetic capacity (maximum rate of net photosynthesis at saturating light) was assessed in 30-year-old open-grown Pinus banksiana Lamb, and 20-year-old open-grown and understory Picea glauca (Moench) Voss in central Alberta. Photosynthesis commenced in early April despite cold soils (0 °C) and night frosts. It fluctuated greatly in the summertime during the periods of summer droughts and stopped abruptly in late October when night air temperature dropped below −10 °C. In comparing seasonal maximums, there was proportionally lower photosynthetic capacity in Pinus banksiana than in Picea glauca in the spring and autumn; however, in the summer, photosynthetic capacity in Pinus banksiana was less variable than in Picea glauca. The fluctuation of photosynthetic capacity in understory Picea glauca saplings was greatly reduced in the summertime compared with open-grown saplings. The data suggest that Picea glauca is able to use the periods of high light in the understory when the aspen is leafless by quickly regaining photosynthetic capacity in the spring and maintaining photosynthesis well into the late autumn. Key words: Picea glauca, Pinus banksiana, photosynthesis, season.
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Nagahatenna, Dilrukshi S. K., Jingwen Tiong, Everard J. Edwards, Peter Langridge e Ryan Whitford. "Altering Tetrapyrrole Biosynthesis by Overexpressing Ferrochelatases (Fc1 and Fc2) Improves Photosynthetic Efficiency in Transgenic Barley". Agronomy 10, n. 9 (11 settembre 2020): 1370. http://dx.doi.org/10.3390/agronomy10091370.
Testo completoAbstract (sommario):
Ferrochelatase (FC) is the terminal enzyme of heme biosynthesis. In photosynthetic organisms studied so far, there is evidence for two FC isoforms, which are encoded by two genes (FC1 and FC2). Previous studies suggest that these two genes are required for the production of two physiologically distinct heme pools with only FC2-derived heme involved in photosynthesis. We characterised two FCs in barley (Hordeum vulgare L.). The two HvFC isoforms share a common catalytic domain, but HvFC2 additionally contains a C-terminal chlorophyll a/b binding (CAB) domain. Both HvFCs are highly expressed in photosynthetic tissues, with HvFC1 transcripts also being abundant in non-photosynthetic tissues. To determine whether these isoforms differentially affect photosynthesis, transgenic barley ectopically overexpressing HvFC1 and HvFC2 were generated and evaluated for photosynthetic performance. In each case, transgenics exhibited improved photosynthetic rate (Asat), stomatal conductance (gs) and carboxylation efficiency (CE), showing that both FC1 and FC2 play important roles in photosynthesis. Our finding that modified FC expression can improve photosynthesis up to ~13% under controlled growth conditions now requires further research to determine if this can be translated to improved yield performance under field conditions.
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Gealy, David R., Sheila A. Squier e Alex G. Ogg. "Photosynthetic Productivity of Mayweed Chamomile (Anthemis cotula)". Weed Science 39, n. 1 (marzo 1991): 18–26. http://dx.doi.org/10.1017/s0043174500057805.
Testo completoAbstract (sommario):
Photosynthetic productivity parameters were determined for mayweed chamomile, a troublesome annual weed of the cropping systems in the Pacific Northwest. At a photosynthetic photon flux density of 1800 μE m−2s–1, maximum net photosynthetic rate of greenhouse-grown plants was 35 mg CO2dm−2h–1and maximum transpiration rate was 6.7 μg H2O cm−2s–1. Dark respiration rate was 1.4 mg CO2dm−2h–1and the light compensation point was 17.5 μE m−2s–1. Carbon dioxide compensation point increased from 25 ppm at 15 C to 43 ppm at 30 C. At saturating photosynthetic photon flux densities, optimum leaf temperature for net photosynthesis was about 25 C. Maximum net photosynthesis of leaves of field-grown plants averaged 15.8 mg CO2dm−2h–1. After a 24-h exposure to 0.075 kg ha–1metribuzin, maximum net photosynthesis and transpiration were reduced 85 and 40%, respectively. Soil water deficits reduced maximum net photosynthesis about 50%.
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Yu-He, Ji, Zhou Guang-Sheng, Ma Xue-Yan, Wang Qiu-Ling e Liu Tao. "Variable photosynthetic sensitivity of maize (Zea mays L.) to sunlight and temperature during drought development process". Plant, Soil and Environment 63, No. 11 (20 novembre 2017): 505–11. http://dx.doi.org/10.17221/664/2017-pse.
Testo completoAbstract (sommario):
The complex interaction process of the abiotic factors (sunlight, air temperature and soil water) in regulating maize (Zea mays L.) photosynthesis has not been fully understood. Our field experiment explored the changed sensitivity (or role) of the abiotic factors in regulating maize photosynthesis under a drought development process. The experiment established a scenario with a long-term drought and an instantaneous cloud cover. The results revealed that long-term drought stress causes the sensitivity (or role) of sunlight and temperature exchanged in regulating maize photosynthesis. The maize photosynthesis was more sensitive to instantaneous sunlight rather than temperature in the absence of drought. However, a diminishing photosynthetic sensitivity to sunlight but an increasing photosynthetic sensitivity to temperature was observed with drought development process. The variable photosynthetic sensitivity indicated that the roles of temperature and sunlight in regulating maize photosynthesis were exchanged, so it is expected that higher photosynthetic rate could be achieved by adjusting temperature rather than sunlight after severe drought. Nevertheless, further studies are needed to provide more evidence and mechanism explanations.
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Hu, Xiche, Thorsten Ritz, Ana Damjanović, Felix Autenrieth e Klaus Schulten. "Photosynthetic apparatus of purple bacteria". Quarterly Reviews of Biophysics 35, n. 1 (febbraio 2002): 1–62. http://dx.doi.org/10.1017/s0033583501003754.
Testo completoAbstract (sommario):
1. Introduction 22. Structure of the bacterial PSU 52.1 Organization of the bacterial PSU 52.2 The crystal structure of the RC 92.3 The crystal structures of LH-II 112.4 Bacteriochlorophyll pairs in LH-II and the RC 132.5 Models of LH-I and the LH-I-RC complex 152.6 Model for the PSU 173. Excitation transfer in the PSU 183.1 Electronic excitations of BChls 22 3.1.1 Individual BChls 22 3.1.2 Rings of BChls 22 3.1.2.1 Exciton states 22 3.1.3 Effective Hamiltonian 24 3.1.4 Optical properties 25 3.1.5 The effect of disorder 263.2 Theory of excitation transfer 29 3.2.1 General theory 29 3.2.2 Mechanisms of excitation transfer 32 3.2.3 Approximation for long-range transfer 34 3.2.4 Transfer to exciton states 353.3 Rates for transfer processes in the PSU 37 3.3.1 Car→BChl transfer 37 3.3.1.1 Mechanism of Car→BChl transfer 39 3.3.1.2 Pathways of Car→BChl transfer 40 3.3.2 Efficiency of Car→BChl transfer 40 3.3.3 B800-B850 transfer 44 3.3.4 LH-II→LH-II transfer 44 3.3.5 LH-II→LH-I transfer 45 3.3.6 LH-I→RC transfer 45 3.3.7 Excitation migration in the PSU 46 3.3.8 Genetic basis of PSU assembly 494. Concluding remarks 535. Acknowledgments 556. References 55Life as we know it today exists largely because of photosynthesis, the process through which light energy is converted into chemical energy by plants, algae, and photosynthetic bacteria (Priestley, 1772; Barnes, 1893; Wurmser, 1925; Van Niel, 1941; Clayton & Sistrom, 1978; Blankenship et al. 1995; Ort & Yocum, 1996). Historically, photosynthetic organisms are grouped into two classes. When photosynthesis is carried out in the presence of air it is called oxygenic photosynthesis (Ort & Yocum, 1996). Otherwise, it is anoxygenic (Blankenship et al. 1995). Higher plants, algae and cyanobacteria perform oxygenic photosynthesis, which involves reduction of carbon dioxide to carbohydrate and oxidation of water to produce molecular oxygen. Some photosynthetic bacteria, such as purple bacteria, carry out anoxygenic photosynthesis that involves oxidation of molecules other than water. In spite of these differences, the general principles of energy transduction are the same in anoxygenic and oxygenic photosynthesis (Van Niel, 1931, 1941; Stanier, 1961; Wraight, 1982; Gest, 1993). The primary processes of photosynthesis involve absorption of photons by light-harvesting complexes (LHs), transfer of excitation energy from LHs to the photosynthetic reaction centers (RCs), and the primary charge separation across the photosynthetic membrane (Sauer, 1975; Knox, 1977; Fleming & van Grondelle, 1994; van Grondelle et al. 1994). In this article, we will focus on the anoxygenic photosynthetic process in purple bacteria, since its photosynthetic system is the most studied and best characterized during the past 50 years.
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Guo, Ying, Tongli Wang, Fang-Fang Fu, Yousry A. El-Kassaby e Guibin Wang. "Metabolome and Transcriptome Analyses Reveal the Regulatory Mechanisms of Photosynthesis in Developing Ginkgo biloba Leaves". International Journal of Molecular Sciences 22, n. 5 (5 marzo 2021): 2601. http://dx.doi.org/10.3390/ijms22052601.
Testo completoAbstract (sommario):
Ginkgo (Ginkgo biloba L.) is a deciduous tree species with high timber, medicinal, ecological, ornamental, and scientific values, and is widely cultivated worldwide. However, for such an important tree species, the regulatory mechanisms involved in the photosynthesis of developing leaves remain largely unknown. Here, we observed variations in light response curves (LRCs) and photosynthetic parameters (photosynthetic capacity (Pnmax) and dark respiration rate (Rd)) of leaves across different developmental stages. We found the divergence in the abundance of compounds (such as 3-phospho-d-glyceroyl phosphate, sedoheptulose-1,7-bisphosphate, and malate) involved in photosynthetic carbon metabolism. Additionally, a co-expression network was constructed to reveal 242 correlations between transcription factors (TFs) and photosynthesis-related genes (p < 0.05, |r| > 0.8). We found that the genes involved in the photosynthetic light reaction pathway were regulated by multiple TFs, such as bHLH, WRKY, ARF, IDD, and TFIIIA. Our analysis allowed the identification of candidate genes that most likely regulate photosynthesis, primary carbon metabolism, and plant development and as such, provide a theoretical basis for improving the photosynthetic capacity and yield of ginkgo trees.
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Sales, Cristina R. G., Yu Wang, Jochem B. Evers e Johannes Kromdijk. "Improving C4 photosynthesis to increase productivity under optimal and suboptimal conditions". Journal of Experimental Botany 72, n. 17 (16 luglio 2021): 5942–60. http://dx.doi.org/10.1093/jxb/erab327.
Testo completoAbstract (sommario):
Abstract Although improving photosynthetic efficiency is widely recognized as an underutilized strategy to increase crop yields, research in this area is strongly biased towards species with C3 photosynthesis relative to C4 species. Here, we outline potential strategies for improving C4 photosynthesis to increase yields in crops by reviewing the major bottlenecks limiting the C4 NADP-malic enzyme pathway under optimal and suboptimal conditions. Recent experimental results demonstrate that steady-state C4 photosynthesis under non-stressed conditions can be enhanced by increasing Rubisco content or electron transport capacity, both of which may also stimulate CO2 assimilation at supraoptimal temperatures. Several additional putative bottlenecks for photosynthetic performance under drought, heat, or chilling stress or during photosynthetic induction await further experimental verification. Based on source–sink interactions in maize, sugarcane, and sorghum, alleviating these photosynthetic bottlenecks during establishment and growth of the harvestable parts are likely to improve yield. The expected benefits are also shown to be augmented by the increasing trend in planting density, which increases the impact of photosynthetic source limitation on crop yields.
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Liao, Ling, Yi Ronga, Xia Qiua, Tiantian Donga e Zhihui Wang. "Photosynthetic model for citrus cultivar Huangguogan". Semina: Ciências Agrárias 41, n. 1 (10 gennaio 2020): 61. http://dx.doi.org/10.5433/1679-0359.2020v41n1p61.
Testo completoAbstract (sommario):
Grafting is an effective measure to improve the photosynthetic rate of citrus. The light responses of photosynthesis in leaves of two-year old grafted Huangguogan (citrus cultivar Huangguogan), Huanggougan / Trifoliate (HG/PT), Huanggougan / Tangerine (HG/CR), and Huanggougan / Ziyang Xiangcheng (HG/CJ) were studied using the LI-COR 6400 portable photosynthesis system. Light-response curves and photosynthetic parameters were analyzed and fitted using the rectangular hyperbola model (RHM), the exponential model (EM), the non rectangular hyperbola model (NRHM), and the modified rectangular hyperbola model (MRHM). The results showed that: (1) Grafting can change the photosynthetic characteristics of Huangguogan, and the value of photosynthesis rate of HG/CJ is the greatest; (2) The light-response curves of net photosynthetic rate (PN), the light compensation point (LCP), and the dark respiration rate (RD) were well fitted using the above four models. The modified rectangular hyperbola was the best model in fitting the data; the nonrectangular hyperbola model was the second, and the rectangular hyperbola model was the poorest one.
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Zagorchev, Lyuben, Alexandra Atanasova, Ivanela Albanova, Anelia Traianova, Petko Mladenov, Margarita Kouzmanova, Vasilij Goltsev, Hazem M. Kalaji e Denitsa Teofanova. "Functional Characterization of the Photosynthetic Machinery in Smicronix Galls on the Parasitic Plant Cuscuta campestris by JIP-Test". Cells 10, n. 6 (5 giugno 2021): 1399. http://dx.doi.org/10.3390/cells10061399.
Testo completoAbstract (sommario):
Members of the genus Cuscuta are generally considered to be non-photosynthetic, stem-holoparasitic flowering plants. Under certain circumstances, at least some members of the genus are capable of limited photosynthesis. The galls of the Smicronyx weevils formed on Cuscuta campestris are particularly rich in chlorophylls compared to the stem of the parasitic plant. In the present study, we aimed to characterize the photosynthetic activity in the inner and outer gall cortices in comparison to the non-photosynthetic stems and a reference plant (Arabidopsis thaliana). The recorded prompt chlorophyll fluorescence transients were analyzed using JIP test. Detailed analysis of the chlorophyll fluorescence confirmed the presence of actively functioning photosynthetic machinery, especially in the inner cortex of the galls. This photosynthesis, induced by the insect larvae, did not reach the levels of the photosynthetic activity in Arabidopsis thaliana plants. Thylakoid protein complexes were identified by separation with two-dimensional Blue Native/SDS PAGE. It appeared that some of the complexes presented in A. thaliana are missing in C. campestris. We hypothesize that the insect-triggered transition from non-photosynthetic to photosynthetic tissue in the gall is driven by the increased requirements for nutrients related to the larval nutrition.
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Lie, Gan Wen, Guang Hua Lie, Hou Zhu Mao e Dong Yu Li. "Study on the Photosynthetic Efficiency of the Bischofia javanica Leaves by Using Photo-Acoustic Tomography Technology". Advanced Materials Research 807-809 (settembre 2013): 596–600. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.596.
Testo completoAbstract (sommario):
By using a new kind of single-beam normalized photo-acoustic tomography spectroscopy (PAS-CT) technology with non-damage detection, the photo-acoustic tomography spectroscopy, optical absorption properties and photosynthetic pigment content of green and red leaves ofBischofia javanicawere studied. The results show that: the photo-acoustic tomography spectroscopy ofBischofia javanicaleaves could be obtained from different chopping frequency and different sample positions, and photosynthetic pigment content of their leaves is closely related to their photosynthetic intensity. The more photosynthetic pigment content the leaves ofBischofia javanicacontain, the bigger optical absorption coefficient and the higher photosynthetic efficiency they have. The photosynthetic pigment content of the green leaves ofBischofia javanicais higher than that of the red ones. As a result, the photosynthesis of green leaves is better than that of the red ones. According to the results of our research, the photosynthetic efficiency ofBischofia javanicacould be improved and its growth time could be effectively controlled to enhance the growth ofBischofia javanica. Furthermore, it could play an important role on the development of forestry, and meet the need of forest for 6 billion people. The research showed high science value to study and applications of the photosynthesis of plants.
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Lukáčová, Alexandra, e Matej Vesteg. "Multiple Independent Losses of Photosynthetic Ability in Eukaryotic Evolution and the Metabolism of Non-Photosynthetic Plastids". Chemické listy 116, n. 5 (15 maggio 2022): 316–23. http://dx.doi.org/10.54779/chl20220316.
Testo completoAbstract (sommario):
Multiple independent losses of photosynthesis have occurred among several unrelated eukaryotic lineages including red and green algae, land plants, alveolates, stramenopiles, cryptophytes and euglenophytes. Most plastid genomes of non-photosynthetic eukaryotes do not contain genes associated with photosynthesis, but they usually encode at least one gene product involved in an essential non-photosynthetic metabolic pathway. Complete loss of plastid genome and simultaneous retention of plastid compartment is rare, and complete plastid loss is documented only for few alveolate species. Non-photosynthetic plastids are often involved in essential fatty acid, isoprenoid, Fe-S cluster, and heme synthesis.
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Bunce, James A. "Species-specific responses to water stress of gas exchange parameters mimicked by applied abscisic acid". Canadian Journal of Botany 65, n. 1 (1 gennaio 1987): 103–6. http://dx.doi.org/10.1139/b87-014.
Testo completoAbstract (sommario):
Net photosynthetic rates and leaf conductances to water vapor were measured in Abutilon theophrasti, Amaranthus hypochondriacus, and Glycine max after injecting abscisic acid into petioles of attached leaves. Changes in substomatal carbon dioxide partial pressure were measured in air in each species for various degrees of inhibition of the photosynthetic rate. Changes in the initial slope of photosynthesis versus substomatal carbon dioxide partial pressure were also characterised in two of the species. Responses to abscisic acid were compared with responses to water stress. Abscisic acid reduced photosynthetic rate and conductance in air in proportion to the amount applied. In no case was the relative decrease in substomatal carbon dioxide partial pressure as large as the relative decrease in photosynthesis. This indicated that nonstomatal inhibition of photosynthesis occurred. The changes in substomatal carbon dioxide partial pressure as photosynthesis was progressively inhibited and the changes in initial slope of photosynthesis versus substomatal carbon dioxide partial pressure were distinct for each species and were the same for abscisic acid and for water stress. The data strongly suggest that the reductions of both photosynthetic capacity and conductance by water stress are mediated by abscisic acid in these species.
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Kumudini, S. "Effect of Radiation and Temperature on Cranberry Photosynthesis and Characterization of Diurnal Change in Photosynthesis". Journal of the American Society for Horticultural Science 129, n. 1 (gennaio 2004): 106–11. http://dx.doi.org/10.21273/jashs.129.1.0106.
Testo completoAbstract (sommario):
Cranberry [Vaccinium macrocarpon (Ait.)] yield has been associated with photosynthate supply. However, the impact of temperature and radiation on photosynthesis of the cranberry plant is not well understood. The objective of this experiment was to characterize the photosynthetic response to radiation and temperature in order to develop a model for estimation of cranberry photosynthetic rates. Two cranberry cultivars, `Stevens' and `Ben Lear', were tested for photosynthetic response at air temperatures ranging from 15 to 35 °C and radiation intensities from 200 to 1200 μmol·m-2·s-1. Depending on temperature, maximum photosynthesis (Pmax) was ≈10 or 12 μmol CO2/m2/s (net photosynthesis) and the saturating radiation level was estimated to be 600 to 800 μmol·m-2·s-1. Cranberry quantum yield was estimated as 0.03 mol CO2/mol photon. Both models; Blackman and the nonrectangular hyperbola with a Θ (angle of curvature) of 0.99 were a good fit for measured photosynthetic rates under controlled environment conditions. The disparity between modeled predicted values, and observed values in the field around midday, indicates a reduction in potential photosynthetic rates in a diurnal cycle that is consistent with the phenomenon of midday depression.
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N'soukpoé-Kossi, C. N., R. Bélanger, S. Keilani, H. Proteau, P. Boivin e R. M. Leblanc. "Short-term acid damage to photosynthesis in corn and sugar maple leaves assessed by photoacoustic spectroscopy". Canadian Journal of Botany 68, n. 10 (1 ottobre 1990): 2292–300. http://dx.doi.org/10.1139/b90-292.
Testo completoAbstract (sommario):
Photoacoustic spectroscopy was used to monitor acid damage to photosynthesis by measuring photosynthetic O2 evolution in leaves from com and sugar maple plantlets. For 2 months the seedlings were treated with simulated acid rain either by spraying the leaves or by watering the soil at different pH levels. The results indicated a decline of photosynthetic oxygen evolution as the pH of the foliar application of simulated acid rain decreased. The reduced photosynthetic activity was sometimes followed by depigmentation (below pH 3.5). For plantlets treated by watering the soil with an acid mixture, the results showed an increase in the growth rate at higher acidity levels without effect on the photosynthetic activity. All corn seedlings from seeds that germinated in media of different pH levels showed the same photosynthetic activity regardless of the pH, as measured by photoacoustic spectroscopy, but the growth rate was higher at lower pH values than at higher pH values. These results clearly indicate the importance of acid damage to photosynthesis at the foliar level, and the ability of photoacoustic spectroscopy to assess forest decline in its early stages. Key words: photoacoustic spectroscopy, photosynthesis, corn, maple, acid rain, oxygen evolution.
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Zhu, Jun-Tao, Xiang-Yi Li, Xi-Ming Zhang, Qiang Yu e Li-Sha Lin. "Leaf nitrogen allocation and partitioning in three groundwater-dependent herbaceous species in a hyper-arid desert region of north-western China". Australian Journal of Botany 60, n. 1 (2012): 61. http://dx.doi.org/10.1071/bt11181.
Testo completoAbstract (sommario):
Groundwater-dependent vegetation (GDV) is useful as an indicator of watertable depth and water availability in north-western China. Nitrogen (N) is an essential limiting resource for growth of GDV. To elucidate how leaf N allocation and partitioning influence photosynthesis and photosynthetic N-use efficiency (PNUE), three typical GDV species were selected, and their photosynthesis, leaf N allocation and partitioning were investigated in the Taklamakan Desert. The results showed that Karelinia caspica (Pall.) Less. and Peganum harmala L. had lower leaf N content, and allocated a lower fraction of leaf N to photosynthesis. However, they were more efficient in photosynthetic N partitioning among photosynthetic components. They partitioned a higher fraction of the photosynthetic N to carboxylation and showed higher PNUE, whereas Alhagi sparsifolia Shap. partitioned a higher fraction of the photosynthetic N to light-harvesting components. For K. caspica and P. harmala, the higher fraction of leaf N was allocated to carboxylation and bioenergetics, which led to a higher maximum net photosynthetic rate, and therefore to a higher PNUE, water-use efficiency (WUE), respiration efficiency (RE) and so on. In the desert, N and water are limiting resources; K. caspica and P. harmala can benefit from the increased PNUE and WUE. These physiological advantages and their higher leaf-area ratio (LAR) may contribute to their higher resource-capture ability.
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Tasnim, Rafa, e Yong-Jiang Zhang. "Are Wild Blueberries a Crop with Low Photosynthetic Capacity? Chamber-Size Effects in Measuring Photosynthesis". Agronomy 11, n. 8 (6 agosto 2021): 1572. http://dx.doi.org/10.3390/agronomy11081572.
Testo completoAbstract (sommario):
Wild lowbush blueberries, an important fruit crop native to North America, contribute significantly to the economy of Maine, USA, Atlantic Canada, and Quebec. However, its photosynthetic capacity has not been well-quantified, with only a few studies showing its low photosynthetic rates. Its small leaves make accurate leaf-level photosynthetic measurements difficult and introduce potential uncertainties in using large leaf chambers. Here, we determined the photosynthetic rate for five different wild blueberry genotypes using a big leaf chamber enclosing multiple leaves and a small leaf chamber with a single leaf to test whether using big leaf chambers (branch-level measurements) underestimates the photosynthetic capacity. Photosynthetic rates of wild blueberries were significantly (35–47%) lower when using the big leaf chamber, and they are not a crop with low photosynthetic capacity, which can be as high as 16 μmol m−2 s−1. Additionally, wild blueberry leaves enclosed in the big chamber at different positions of a branch did not differ in chlorophyll content and photosynthetic rate, suggesting that the difference was not caused by variation among leaves but probably due to leaf orientations and self-shading in the big chamber. A significant linear relationship between the photosynthetic rate measured by the small and big leaf chambers suggests that the underestimation in leaf photosynthetic capacity could be corrected. Therefore, chamber-size effects need to be considered in quantifying photosynthetic capacity for small-leaf crops, and our study provided important guidelines for future photosynthesis research. We also established the relationship between the Electron Transport Rate (ETR) and photosynthetic CO2 assimilation for wild blueberries. ETR provides an alternative to quantify photosynthesis, but the correlation coefficient of the relationship (R2 = 0.65) suggests that caution is needed in this case.
21
Evans, JR. "Photosynthetic Acclimation and Nitrogen Partitioning Within a Lucerne Canopy. II. Stability Through Time and Comparison With a Theoretical Optimum". Functional Plant Biology 20, n. 1 (1993): 69. http://dx.doi.org/10.1071/pp9930069.
Testo completoAbstract (sommario):
Nitrogen redistribution between and within leaves was examined in a plot of lucerne (Medicago sativa L. cv. Aurora) in relation to potential canopy photosynthesis. The canopy was sampled during regrowth after cutting and just prior to flowering. As leaves were progressively shaded by the newly produced leaves, nitrogen content fell and photosynthetic acclimation occurred. The rate of acclimation in the canopy was the same as occurred following a step change to 23 or 6% sunlight. The profile of leaf nitrogen content was stable with respect to leaf area index and independent of time of sampling. Optimal profiles of nitrogen distribution between leaves, photosynthetic rate per unit chlorophyll and nitrogen partitioning within leaves were calculated from the relationships between photosynthesis and nitrogen in conjunction with the light environment of the preceding 3 days. The optimal nitrogen content of the leaves should vary in proportion to the relative daily irradiance at each leaf. The observed distribution achieved 88% of the potential daily photosynthesis, while a uniform nitrogen distribution yielded only 80%. Photosynthetic acclimation and nitrogen partitioning within each leaf both responded to daily irradiance similarly to the calculated optimum except at the two extremes. At the top of the canopy, photosynthetic rate per unit of chlorophyll did not increase as much as the calculated optimum, while at the base of the canopy, nitrogen partitioning failed to fall as much as the calculated optimum. This may reflect the constraints on the flexibility of the photosynthetic system. Nitrogen redistribution between leaves made a dramatic contribution to increasing the potential photosynthesis by the canopy. Although acclimation to low irradiance reduced the photosynthetic capacity per unit nitrogen by 12%, the considerable reorganisation of proteins within the thylakoids increased potential daily photosynthesis by 20% over that which would have been gained by a 'sun' leaf. However, in terms of canopy photosynthesis, which is dominated by leaves intercepting most of the light, acclimation contributed only a few per cent to the potential daily canopy photosynthesis.
22
Nie, Xin, Andreas Jäger, Janek Börner e Gabriele Klug. "Interplay between formation of photosynthetic complexes and expression of genes for iron–sulfur cluster assembly in Rhodobacter sphaeroides?" Photosynthesis Research 147, n. 1 (16 ottobre 2020): 39–48. http://dx.doi.org/10.1007/s11120-020-00789-w.
Testo completoAbstract (sommario):
AbstractFormation of photosynthetic complexes leads to a higher demand for Fe–S clusters. We hypothesized that in the facultative phototrophic alpha-proteobacterium Rhodobacter sphaeroides expression of the isc-suf operon for Fe–S cluster formation may be increased under conditions that promote formation of photosynthetic complexes and that, vice versa, lack of the IscR regulator may also affect photosynthesis gene expression. To test this hypothesis, we monitored the activities of the isc-suf sense and anti-sense promoters under different growth conditions and in mutants which are impaired in formation of photosynthetic complexes. We also tested expression of photosynthesis genes in a mutant lacking the IscR regulator. Our results are not in agreement with a co-regulation of the Isc-Suf system and the photosynthetic apparatus at level of transcription. We provide evidence that, coordination of the systems occurs at post-transcriptional levels. Increased levels of isc-suf mRNAs under conditions promoting formation of photosynthetic complexes are due to higher RNA stability.
23
Warnock, Daniel, William Randle e Mark Rieger. "PHOTOSYNTHESIS AND TRANSPIRATION DURING GROWTH AND DEVELOPMENT OF ALLIUM CEPA L." HortScience 28, n. 4 (aprile 1993): 263B—263. http://dx.doi.org/10.21273/hortsci.28.4.263b.
Testo completoAbstract (sommario):
Photosynthesis is the very essence of agriculture. Previous photosynthetic and transpirational studies of onion (Allium cepa) have been limited to specific developmental stages. Our study measured photosynthesis and transpiration in sixteen plants of a single short-day cultivar over an eleven week period containing both non- and bulb inductive photoperiods. Differences in weekly means for photosynthesis, leaf conductance, water use efficiency, and intercellular CO, were highly significant. Weekly photosynthetic means increased under a non-inductive photoperiod and peaked one week after initiating a bulb inducing photoperiod. A decrease and leveling period occurred as bulbs developed followed by a decrease as foliage lodged. Weekly photosynthetic and leaf conductance means were correlated and highly significant. Water use efficiency and intercellular CO, means remained fairly constant throughout the study suggesting that photosynthesis in unstressed onions was controlled by internal mechanisms instead of stomata.
24
Urban, Aleksandra, Paweł Rogowski, Wioleta Wasilewska-Dębowska e Elżbieta Romanowska. "Understanding Maize Response to Nitrogen Limitation in Different Light Conditions for the Improvement of Photosynthesis". Plants 10, n. 9 (16 settembre 2021): 1932. http://dx.doi.org/10.3390/plants10091932.
Testo completoAbstract (sommario):
The photosynthetic capacity of leaves is determined by their content of nitrogen (N). Nitrogen involved in photosynthesis is divided between soluble proteins and thylakoid membrane proteins. In C4 plants, the photosynthetic apparatus is partitioned between two cell types: mesophyll cells and bundle sheath. The enzymes involved in the C4 carbon cycle and assimilation of nitrogen are localized in a cell-specific manner. Although intracellular distribution of enzymes of N and carbon assimilation is variable, little is known about the physiological consequences of this distribution caused by light changes. Light intensity and nitrogen concentration influence content of nitrates in leaves and can induce activity of the main enzymes involved in N metabolism, and changes that reduce the photosynthesis rate also reduce photosynthetic N use efficiency. In this review, we wish to highlight and discuss how/whether light intensity can improve photosynthesis in maize during nitrogen limitation. We described the general regulation of changes in the main photosynthetic and nitrogen metabolism enzymes, their quantity and localization, thylakoid protein abundance, intracellular transport of organic acids as well as specific features connected with C4 photosynthesis, and addressed the major open questions related to N metabolism and effects of light on photosynthesis in C4 plants.
25
Chang, Tian-Gen, Zai Shi, Honglong Zhao, Qingfeng Song, Zhonghu He, Jeroen Van Rie, Bart Den Boer, Alexander Galle e Xin-Guang Zhu. "3dCAP-Wheat: An Open-Source Comprehensive Computational Framework Precisely Quantifies Wheat Foliar, Nonfoliar, and Canopy Photosynthesis". Plant Phenomics 2022 (21 luglio 2022): 1–19. http://dx.doi.org/10.34133/2022/9758148.
Testo completoAbstract (sommario):
Canopy photosynthesis is the sum of photosynthesis of all above-ground photosynthetic tissues. Quantitative roles of nonfoliar tissues in canopy photosynthesis remain elusive due to methodology limitations. Here, we develop the first complete canopy photosynthesis model incorporating all above-ground photosynthetic tissues and validate this model on wheat with state-of-the-art gas exchange measurement facilities. The new model precisely predicts wheat canopy gas exchange rates at different growth stages, weather conditions, and canopy architectural perturbations. Using the model, we systematically study (1) the contribution of both foliar and nonfoliar tissues to wheat canopy photosynthesis and (2) the responses of wheat canopy photosynthesis to plant physiological and architectural changes. We found that (1) at tillering, heading, and milking stages, nonfoliar tissues can contribute ~4, ~32, and ~50% of daily gross canopy photosynthesis (Acgross; ~2, ~15, and ~-13% of daily net canopy photosynthesis, Acnet) and absorb ~6, ~42, and ~60% of total light, respectively; (2) under favorable condition, increasing spike photosynthetic activity, rather than enlarging spike size or awn size, can enhance canopy photosynthesis; (3) covariation in tissue respiratory rate and photosynthetic rate may be a major factor responsible for less than expected increase in daily Acnet; and (4) in general, erect leaves, lower spike position, shorter plant height, and proper plant densities can benefit daily Acnet. Overall, the model, together with the facilities for quantifying plant architecture and tissue gas exchange, provides an integrated platform to study canopy photosynthesis and support rational design of photosynthetically efficient wheat crops.
26
Lie, Gan Wen, Guang Hua Lie, Ding Chao Pan, Long Hua Ye e Dong Yu Li. "Study on the Photosynthetic Efficiency of the Bauhinia blakeana Leaves by Using Photo-Acoustic Tomography Technology". Advanced Materials Research 807-809 (settembre 2013): 1010–14. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.1010.
Testo completoAbstract (sommario):
By using a new kind of single-beam normalized photo-acoustic tomography spectroscopy (PAS-CT) technology with non-damage detection, the photo-acoustic tomography spectroscopy and optical absorption properties of green and yellow leaves ofBauhinia blakeanawere studied. The results show that: the photo-acoustic tomography spectroscopy ofBauhinia blakeanaleaves could be obtained from different chopping frequency and different sample positions, and photosynthetic pigment content of their leaves is closely related to their photosynthetic intensity. The more photosynthetic pigment content the leaves ofBauhinia blakeanacontain, the bigger optical absorption coefficient and the higher photosynthetic efficiency they have. The photosynthetic pigment content of the green leaves ofBauhinia blakeanais higher than that of the yellow ones. As a result, the photosynthesis of green leaves is better than that of the yellow ones. According to the results of our research, the photosynthetic efficiency ofBauhinia blakeanacould be improved and its growth time could be effectively controlled to enhance the growth ofBauhinia blakeana. Furthermore, it could play an important role on the development of forestry, and meet the need of forest for 6 billion people. The research showed high science value to the study and applications of the photosynthesis of plants.
27
Claypool, Nicholas B., e J. Heinrich Lieth. "Green Light Improves Photosystem Stoichiometry in Cucumber Seedlings (Cucumis sativus) Compared to Monochromatic Red Light". Plants 10, n. 5 (21 aprile 2021): 824. http://dx.doi.org/10.3390/plants10050824.
Testo completoAbstract (sommario):
It has been shown that monochromatic red and blue light influence photosynthesis and morphology in cucumber. It is less clear how green light impacts photosynthetic performance or morphology, either alone or in concert with other wavelengths. In this study, cucumber (Cucumis sativus) was grown under monochromatic blue, green, and red light, dichromatic blue–green, red–blue, and red–green light, as well as light containing red, green, and blue wavelengths, with or without supplemental far-red light. Photosynthetic data collected under treatment spectra at light-limiting conditions showed that both red and green light enhance photosynthesis. However, photosynthetic data collected with a 90% red, 10% blue, 1000 µmol photons m−2 s−1, saturating light show significantly lower photosynthesis in the green, red, and red–green treatments, indicating a blue light enhancement due to photosystem stoichiometric differences. The red–green and green light treatments show improved photosynthetic capacity relative to red light, indicating partial remediation by green light. Despite a lower quantum efficiency and the lowest ambient photosynthesis levels, the monochromatic blue treatment produced among the tallest, most massive plants with the greatest leaf area and thickest stems.
28
Bhagsari, Ajmer S. "Photosynthetic Evaluation of Sweetpotato Germplasm". Journal of the American Society for Horticultural Science 115, n. 4 (luglio 1990): 634–39. http://dx.doi.org/10.21273/jashs.115.4.634.
Testo completoAbstract (sommario):
Field experiments were conducted from 1980-1983 to evaluate sweetpotato [Ipomoea batatas (L.) Lam.] germplasm for photosynthetic efficiency, harvest index [HI; (storage root dry matter/total plant dry matter) × 100], and yield. Most genotypes maintained leaf area index (LAI) above five until final harvest, 164 days after planting (DAP). The higher LAI (> 8) for PI 318859, PI 344134, and PI 308205 compared to the other genotypes was maintained at the expense of the storage root development. Single leaf net photosynthesis (Pn) of the genotypes ranged from 0.61 to 1.09 mg CO2/m2 per sec during 1980. Canopy photosynthesis on a ground area (CPn-Ga) basis ranged from 0.95 to 1.56 and 1.04 to 1.30 mg CO2/m2 per sec during July and August 1983, respectively. Canopy photosynthesis expressed on leaf dry-weight (CPn-Dwt) basis was higher for PI 344122 than the other genotypes, except PI 344138, indicating its superior photosynthetic efficiency. Photosynthetic efficiency and stomatal conductance were not related to yield. Stomatal conductance and CPn-Ga were significantly correlated. Harvest index differed significantly at each sampling and ranged from 14.0% to 75.5% at final harvest. Fresh storage root yield for 1983 and 4-year mean yield ranged from 8.6 to 60.1 and 14.1 to 42.2 t·ha-1 respectively. At final harvest, HI correlated significantly with fresh-(r = 0.91) and dry-matter storage root yield (r = 0.95). Despite significant photosynthetic variations among the genotypes, sweetpotato yield was influenced more by HI and storage root sink strength than by photosynthetic efficiency.
29
Ribeiro, Rafael Vasconcelos, Eduardo Caruso Machado e Ricardo Ferraz de Oliveira. "Temperature response of photosynthesis and its interaction with light intensity in sweet orange leaf discs under non-photorespiratory condition". Ciência e Agrotecnologia 30, n. 4 (agosto 2006): 670–78. http://dx.doi.org/10.1590/s1413-70542006000400012.
Testo completoAbstract (sommario):
This study aimed to evaluate the response of photosynthesis (A), given by photosynthetic O2 evolution, to increasing temperature from 25 to 50ºC in sweet orange (Citrus sinensis (L.) Osbeck) leaf discs under non-photorespiring conditions. In order to evaluate the response of gross photosynthesis to temperature and the balance between photosynthetic and respiratory activities, respiration (Rd) rates were also measured, i.e. the O2 uptake in each temperature. In addition, light response curves of photosynthesis were performed by varying the photosynthetic photon flux density (PPFD) from 0 to 1160 µmol m-2 s-1 at 25 and 40ºC. The highest A values were observed at 35 and 40ºC, whereas the highest Rd values were noticed at 50ºC. A higher relationship A/Rd was found at 30 and 35ºC, suggesting an optimum temperature of 35ºC when considering the balance between photosynthesis and respiration under non-photorespiring condition. Overall, heat effects on plant metabolism were more evident when evaluating the relationship A/Rd. In light response curves, higher A values were also found at 40ºC under PPFD higher than 300 µmol m-2 s-1. Light saturation point of photosynthesis was increased at 40ºC, without significant change of quantum efficiency under low PPFD. Respiration was also enhanced at 40ºC, and as a consequence, the light compensation point increased. The better photosynthetic performance at 35-40ºC was supported by higher photochemical efficiency in both light and temperature response curves. The temperature-dependence of photosynthesis was affected by growth temperature, i.e. a high air temperature during plant growth is a probable factor leading to a higher photosynthetic tolerance to heat stress.
30
Li, Yong. "Evaluation of Photosynthetic Characters and Regulation Pattern of Photosynthesis Associated Gene in Two Mulberry Varieties". International Journal of Agriculture and Biology 25, n. 04 (1 aprile 2021): 863–72. http://dx.doi.org/10.17957/ijab/15.1740.
Testo completoAbstract (sommario):
Photosynthetic characteristics and expression patterns of the photosynthesis-related genes in the high-yield mulberry variety E’Sang 1 (E1) and normal mulberry variety Husang 32 (H32) were investigated in this study. The observation of daily variation of photosynthesis in E1 and H32 indicated that the peak of net photosynthetic rate(Pn)inE1 variety was significantly higher than that inH32 (P <0.05). Meanwhile, the Pn-PAR and Pn-Ci responses of E1 and H32 were evaluated, and the results showed that the carboxylation efficiency and compensation saturation point were much higher in E1 rather thanH32. Importantly, the photosystem II actual photochemical efficiency and photochemical quenching coefficient in the leaves of E1 were significantly higher than those in H32 (P<0.05). Also, the activity of RuBP in E1 was higher than that in H32 (P >0.05). Based on the RNA-seq data, a total of 3,356 differentially expressed genes (DEGs) were detected among different time points between E1 and H32. Of these, 1,136 DEGs were involved in the metabolic pathways, including three main photosynthesis-related metabolic pathways (i.e., carbon fixation in photosynthetic organisms, carbon metabolism, and porphyrin and chlorophyll metabolism). Meanwhile, 10 novel DEGs related to photosynthesis were detected, and four potential key genes of them could account for the differences in net photosynthetic rate and yield betweenH32 and E1.This study could provide important insights into the molecular breeding of mulberry varieties with high photosynthetic efficiency and contribute to understanding the genetic mechanism of photosynthesis.© 2021 Friends Science Publishers
31
Vidaver, William, Wolfgang Binder, R. C. Brooke, G. R. Lister e P. M. A. Toivonen. "Assessment of photosynthetic activity of nursery-grown Piceaglauca seedlings using an integrating fluorometer to monitor variable chlorophyll fluorescence". Canadian Journal of Forest Research 19, n. 11 (1 novembre 1989): 1478–82. http://dx.doi.org/10.1139/x89-224.
Testo completoAbstract (sommario):
Photosynthetic activity of intact nursery-grown white spruce (Piceaglauca (Moench) Voss) seedlings was assessed by measuring CO2 exchange (apparent photosynthesis) and normalized, integrated variable chlorophyll fluorescence emission. Agreement between fluorescence and apparent photosynthesis indicated that photosynthetic inactivation of seedlings from selected seedlots began in mid-August and approached completion in late October. Inactivation occurred somewhat earlier in northern seedlot seedlings than in those from a more southerly provenance. Seedlings tested in late October showed significant photosynthetic inactivation, as indicated by both fluorescence and apparent photosynthesis. These seedlings also had passed the −18 °C frost hardiness test currently used in British Columbia as an indicator for safe lifting. On removal from −2 °C storage, seedlings lifted and stored according to nursery practises showed fluorescence emission indicative of photosynthetic reactivation and also had high root growth capacity scores. Low root growth capacity scores were associated with delayed or incomplete photosynthetic reactivation. These results show that fluorescence assessment provides information about the physiological status of white spruce seedlings. Variable fluorescence assays are nondestructive and can be made and interpreted within minutes. As an indicator of shoot metabolic activity, fluorescence assessment provides information useful in selecting lifting dates and in evaluating the effects of dark cold storage on white spruce seedlings.
32
Marcos-Arenal, Pablo, Luis Cerdán, Mercedes Burillo-Villalobos, Nuria Fonseca-Bonilla, Juan García de la Concepción, María Ángeles López-Cayuela, Felipe Gómez e José A. Caballero. "ExoPhot: The Photon Absorption Rate as a New Metric for Quantifying the Exoplanetary Photosynthetic Activity Fitness". Universe 8, n. 12 (26 novembre 2022): 624. http://dx.doi.org/10.3390/universe8120624.
Testo completoAbstract (sommario):
Only a low percentage of the radiation from our Sun is captured by photosynthesis, but this conversion of solar to chemical energy sustains all life on Earth. Photosynthesis could be present in any exoplanetary system fulfilling the main three ingredients for this metabolic route: light, water, and carbon dioxide. To deepen into this idea, the ExoPhot project aims to study the relation between photosynthetic systems and exoplanet conditions around different types of stars by focusing on two aspects: (i) Assessing the photosynthetic fitness of a variety of photopigments (either found on Earth or theoretical) as a function of stellar spectral type, star-exoplanet separation, and planet atmosphere basic parameters, and (ii) delineating a range of stellar, exoplanet, and atmospheric parameters for which photosynthetic activity might be feasible. In order to address these goals, we make use of a new metric, the absorption rate γ, for the evaluation of the exoplanet photosynthetic activity that, based on state-of-the-art planet atmosphere and stellar photosphere spectroscopic models, quantifies the overlap between those models with the absorption spectra of photosynthetic pigments, both terrestrial and theoretical. We provide with a set of results for a combination of photosystems and exoplanetary environments revealing the importance of our metric when compared to previous photosynthesis indicators.
33
Groninger, J. W., J. R. Seiler, S. M. Zedaker e P. C. Berrang. "Photosynthetic response of loblolly pine and sweetgum seedling stands to elevated carbon dioxide, water stress, and nitrogen level". Canadian Journal of Forest Research 26, n. 1 (1 gennaio 1996): 95–102. http://dx.doi.org/10.1139/x26-010.
Testo completoAbstract (sommario):
Seedling stands of loblolly pine (Pinustaeda L.) and sweetgum (Liquidambarstyraciflua L.) were grown in monoculture or mixed stands for two growing cycles in controlled-environment chambers. Treatments consisted of ambient (408 ppm) and elevated (806 ppm) CO2, concentrations, water-stressed and well-watered conditions, and low (20 kg N/ha) and high (215 kg N/ha) nitrogen application rates. Photosynthesis rates were measured under ambient and elevated cuvette CO2 concentrations for both whole stands and individual seedlings from these stands. Significant interactions between CO2 and water suggested that elevated CO2 concentration compensated for low water availability in individually measured loblolly pine and in whole seedling stands regardless of stand type. Expressing photosynthesis on a soil area versus a leaf-mass basis influenced the photosynthetic rankings of the three stand types relative to one another. Net photosynthetic rates per unit leaf mass were 390 and 880% higher in individually measured seedlings than in whole monoculture stands for loblolly pine and sweetgum, respectively. Lower photosynthetic contributions from lower canopy leaves in whole seedling stands compared with the upper canopy leaves used in individual-seedling measurements were thought to be responsible for lower photosynthetic rates in seedling stands. These results suggest that photosynthetic response is influenced by canopy dynamics that are unaccounted for by individual-seedling measurements of photosynthesis. Differences in photosynthetic response between loblolly pine and sweetgum stands and individuals are thought to be largely due to species-specific differences in canopy light extinction characteristics.
34
Munger, Philip H., James M. Chandler e J. Tom Cothren. "Effect of Water Stress on Photosynthetic Parameters of Soybean (Glycine max) and Velvetleaf (Abutilon theophrasti)". Weed Science 35, n. 1 (gennaio 1987): 15–21. http://dx.doi.org/10.1017/s0043174500026722.
Testo completoAbstract (sommario):
Greenhouse experiments were conducted to elucidate the effects of water stress on photosynthetic parameters of soybean [Glycine max(L.) Merr. ‘Hutton′] and velvetleaf (Abutilon theophrastiMedik. # ABUTH). Stomatal conductance of both species responded curvilinearly to reductions in leaf water potential. At leaf water potentials less negative than −2.5 MPa, stomatal conductance, net photosynthetic rate, and transpiration rate were greater in velvetleaf than in soybean. Soybean photosynthetic rate was linearly related to stomatal conductance. Velvetleaf photosynthetic rate increased linearly with stomatal conductances up to 1.5 cm s–1; however, no increase in photosynthetic rate was observed at stomatal conductances greater than 1.5 cm s–1, indicating nonstomatal limitations to photosynthesis. As water stress intensified, stomatal conductance, photosynthetic rate, and transpiration of velvetleaf declined more rapidly than in soybean.
35
Xu, Ming Yi, Ao Xue Wang e Hong Wei Ni. "Effect of Elevated CO2 Concentration on Leaf Photosynthesis in Sanjiang-Deyeuxia angustifolia". Advanced Materials Research 726-731 (agosto 2013): 305–9. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.305.
Testo completoAbstract (sommario):
Deyeuxia angustifolia were grown under three different levels of CO2concentration conditions, 370μmol mol-1(ambient CO2), 550μmol mol-1(elevated CO2) and 700μmol mol-1(elevated CO2) respectively. We investigated the responses of photosynthesis and growth ofD.angustifoliaunder different CO2concentration conditions. Leaf photosynthesis and chlorophyll content were checked. The results showed that the values of net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2concentration (Ci), transpiration (E), chlorophyll content were influenced by the elevated CO2concentrations. The photosynthetic parameters changed in parallel with CO2enrichment. CO2enrichment in short term improved the photosynthetic ability of leaves, whereas the capacity was weakened under long-term elevated CO2concentration condition. The leaves ofD.angustifoliagrown under elevated CO2concentrations at the end of growth, had lower Pn, Gs, Ci, E and chlorophyll content than those grown and measuered under ambient CO2concentration. The results indicated thatD.angustifoliaappeared photosynthetic acclimation.
36
Bouhache, Mohamed, e David E. Bayer. "Photosynthetic Response of Flooded Rice (Oryza sativa) and ThreeEchinochloaSpecies to Changes in Environmental Factors". Weed Science 41, n. 4 (dicembre 1993): 611–14. http://dx.doi.org/10.1017/s0043174500076402.
Testo completoAbstract (sommario):
The photosynthetic responses of rice (C3) and threeEchinochloaspecies (C4), barnyardgrass, early watergrass, and late watergrass, to changes in CO2intercellular partial pressure, light intensity, and leaf temperature were investigated under laboratory conditions. The threeEchinochloaspecies exhibited photosynthetic responses characteristic of C4plants. The three weedy species showed higher efficiency for CO2utilization at low CO2intercellular partial pressure (CO2i) than rice. Compensation and saturation of CO2i for photosynthesis were lower in the weedy species than in rice. The maximum photosynthetic rates at high light intensity were 33.5, 32.7, 30.5, and 21.5 μmol CO2m-2s-1for barnyardgrass, early watergrass, late watergrass, and rice, respectively. Photosynthesis temperature optimum was 35 to 37 C for the threeEchinochloaspecies and 33 C for rice. Overall, under simulated summer conditions, the four taxa showed a photosynthetic ability hierarchy with regard to gas exchange performance as follows: barnyardgrass ≥ early watergrass > late watergrass > rice.
37
Kroh, Gretchen E., e Marinus Pilon. "Regulation of Iron Homeostasis and Use in Chloroplasts". International Journal of Molecular Sciences 21, n. 9 (11 maggio 2020): 3395. http://dx.doi.org/10.3390/ijms21093395.
Testo completoAbstract (sommario):
Iron (Fe) is essential for life because of its role in protein cofactors. Photosynthesis, in particular photosynthetic electron transport, has a very high demand for Fe cofactors. Fe is commonly limiting in the environment, and therefore photosynthetic organisms must acclimate to Fe availability and avoid stress associated with Fe deficiency. In plants, adjustment of metabolism, of Fe utilization, and gene expression, is especially important in the chloroplasts during Fe limitation. In this review, we discuss Fe use, Fe transport, and mechanisms of acclimation to Fe limitation in photosynthetic lineages with a focus on the photosynthetic electron transport chain. We compare Fe homeostasis in Cyanobacteria, the evolutionary ancestors of chloroplasts, with Fe homeostasis in green algae and in land plants in order to provide a deeper understanding of how chloroplasts and photosynthesis may cope with Fe limitation.
38
Suarez, Julio V., Elisabeth A. Mudd e Anil Day. "A Chloroplast-Localised Fluorescent Protein Enhances the Photosynthetic Action Spectrum in Green Algae". Microorganisms 10, n. 9 (1 settembre 2022): 1770. http://dx.doi.org/10.3390/microorganisms10091770.
Testo completoAbstract (sommario):
Green microalgae are important sources of natural products and are attractive cell factories for manufacturing high-value products such as recombinant proteins. Increasing scales of production must address the bottleneck of providing sufficient light energy for photosynthesis. Enhancing the photosynthetic action spectrum of green algae to improve the utilisation of yellow light would provide additional light energy for photosynthesis. Here, we evaluated the Katushka fluorescent protein, which converts yellow photons to red photons, to drive photosynthesis and growth when expressed in Chlamydomonas reinhardtii chloroplasts. Transplastomic algae expressing a codon-optimised Katushka gene accumulated the active Katushka protein, which was detected by excitation with yellow light. Removal of chlorophyll from cells, which captures red photons, led to increased Katushka fluorescence. In yellow light, emission of red photons by fluorescent Katushka increased oxygen evolution and photosynthetic growth. Utilisation of yellow photons increased photosynthetic growth of transplastomic cells expressing Katushka in light deficient in red photons. These results showed that Katushka was a simple and effective yellow light-capturing device that enhanced the photosynthetic action spectrum of C. reinhardtii.
39
Nikkanen, Lauri, e Eevi Rintamäki. "Chloroplast thioredoxin systems dynamically regulate photosynthesis in plants". Biochemical Journal 476, n. 7 (15 aprile 2019): 1159–72. http://dx.doi.org/10.1042/bcj20180707.
Testo completoAbstract (sommario):
Abstract Photosynthesis is a highly regulated process in photoautotrophic cells. The main goal of the regulation is to keep the basic photosynthetic reactions, i.e. capturing light energy, conversion into chemical energy and production of carbohydrates, in balance. The rationale behind the evolution of strong regulation mechanisms is to keep photosynthesis functional under all conditions encountered by sessile plants during their lifetimes. The regulatory mechanisms may, however, also impair photosynthetic efficiency by overriding the photosynthetic reactions in controlled environments like crop fields or bioreactors, where light energy could be used for production of sugars instead of dissipation as heat and down-regulation of carbon fixation. The plant chloroplast has a high number of regulatory proteins called thioredoxins (TRX), which control the function of chloroplasts from biogenesis and assembly of chloroplast machinery to light and carbon fixation reactions as well as photoprotective mechanisms. Here, we review the current knowledge of regulation of photosynthesis by chloroplast TRXs and assess the prospect of improving plant photosynthetic efficiency by modification of chloroplast thioredoxin systems.
40
Smolova, Tatiana, Andrew Khorobrykh e Tatyana Savchenko. "Cortical photosynthesis as a physiological marker for grape breeding: methods and approaches". BIO Web of Conferences 25 (2020): 02018. http://dx.doi.org/10.1051/bioconf/20202502018.
Testo completoAbstract (sommario):
Photosynthesis occurring in chlorenchymal tissues of lignified branches of perennial plants (cortical photosynthesis) has a significant impact on their productivity and resistance to adverse environmental conditions, such as water deficiency and low temperatures. Cortical photosynthesis occurring under the outer bark of a lignified grape vine can become a convenient marker for breeding freeze-tolerant varieties. The following approaches can be undertaken to assess the functional state of the cortical photosynthetic apparatus: (1) analysis of the variable chlorophyll fluorescence parameters and (2) biochemical analysis of photosynthetic membrane preparations. To evaluate these approaches, in this work we have carried out the comparative analysis of characteristics of the cortical photosynthetic apparatus in grape varieties differing in freeze tolerance. This work was supported by grant №18-04-00079 from the Russian Foundation for Basic Research.
41
Wu, Yanyou. "Is bicarbonate directly used as substrate to participate in photosynthetic oxygen evolution". Acta Geochimica 40, n. 4 (21 giugno 2021): 650–58. http://dx.doi.org/10.1007/s11631-021-00484-0.
Testo completoAbstract (sommario):
AbstractIf the photosynthetic organisms assimilated only CO2 in the Archean atmosphere, hydroxide ion in the Archean seawater would not increase. If plants would not consume bicarbonate as a direct substrate during photosynthesis, it is difficult to explain the evolution of Earth's environment. To date, it is generally accepted that photosynthetic O2 evolution of plants come from water photolysis. However, it should be debated by evaluating the effect of bicarbonate in photosynthetic O2 evolution, analyzing the role of carbonic anhydrase (CA) in photosynthetic O2 evolution, and the relationship between thylakoid CA and photosynthetic O2 evolution. In the paper, I propose that bicarbonate is directly used as substrate to participate in photosynthetic O2 evolution. The rationality of bicarbonate photolysis of plants is discussed from the thermodynamics and evolution of Earth's environment. The isotopic evidence that bicarbonate is not the direct substrate of photosynthetic O2 release is reexamined, and the new explanation of bicarbonate photolysis in photosynthetic O2 evolution is proposed.
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Zhang, Zimeng, Long-Sheng Zhao e Lu-Ning Liu. "Characterizing the supercomplex association of photosynthetic complexes in cyanobacteria". Royal Society Open Science 8, n. 7 (luglio 2021): 202142. http://dx.doi.org/10.1098/rsos.202142.
Testo completoAbstract (sommario):
The light reactions of photosynthesis occur in thylakoid membranes that are densely packed with a series of photosynthetic complexes. The lateral organization and close association of photosynthetic complexes in native thylakoid membranes are vital for efficient light harvesting and energy transduction. Recently, analysis of the interconnections between photosynthetic complexes to form supercomplexes has garnered great interest. In this work, we report a method integrating immunoprecipitation, mass spectrometry and atomic force microscopy to identify the inter-complex associations of photosynthetic complexes in thylakoid membranes from the cyanobacterium Synechococcus elongatus PCC 7942. We characterize the preferable associations between individual photosynthetic complexes and binding proteins involved in the complex–complex interfaces, permitting us to propose the structural models of photosynthetic complex associations that promote the formation of photosynthetic supercomplexes. We also identified other potential binding proteins with the photosynthetic complexes, suggesting the highly connecting networks associated with thylakoid membranes. This study provides mechanistic insight into the physical interconnections of photosynthetic complexes and potential partners, which are crucial for efficient energy transfer and physiological acclimatization of the photosynthetic apparatus. Advanced knowledge of the protein organization and interplay of the photosynthetic machinery will inform rational design and engineering of artificial photosynthetic systems to supercharge energy production.
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Vieira Jr., Jair, e Orlando Necchi Jr. "Photosynthetic characteristics of a tropical population of Nitella cernua (Characeae, Chlorophyta)". Brazilian Journal of Plant Physiology 18, n. 3 (settembre 2006): 379–88. http://dx.doi.org/10.1590/s1677-04202006000300004.
Testo completoAbstract (sommario):
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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Jiang, Ze-Yu, e Carl E. Bauer. "Component of the Rhodospirillum centenum Photosensory Apparatus with Structural and Functional Similarity to Methyl-Accepting Chemotaxis Protein Chemoreceptors". Journal of Bacteriology 183, n. 1 (1 gennaio 2001): 171–77. http://dx.doi.org/10.1128/jb.183.1.171-177.2001.
Testo completoAbstract (sommario):
ABSTRACT Photosynthetic bacteria respond to alterations in light conditions by migrating to locations that allows optimal use of light as an energy source. Studies have indicated that photosynthesis-driven electron transport functions as an attractant signal for motility among purple photosynthetic bacteria. However, it is unclear just how the motility-based signal transduction system monitors electron flow through photosynthesis-driven electron transport. Recently, we have demonstrated that the purple photosynthetic bacteriumRhodospirillum centenum is capable of rapidly moving swarm cell colonies toward infrared light as well as away from visible light. Light-driven colony motility of R. centenum has allowed us to perform genetic dissection of the signaling pathway that affects photosynthesis-driven motility. In this study, we have undertaken sequence and mutational analyses of one of the components of a signal transduction pathway, Ptr, which appears responsible for transmitting a signal from the photosynthesis-driven electron transport chain to the chemotaxis signal transduction cascade. Mutational analysis demonstrates that cells disrupted for ptr are defective in altering motility in response to light, as well as defective in light-dependent release of methanol. We present a model which proposes that Ptr senses the redox state of a component in the photosynthetic cyclic electron transport chain and that Ptr is responsible for transmitting a signal to the chemotaxis machinery to induce a photosynthesis-dependent motility response.
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李, 明星. "Research Progress of Photosynthetic Proteins in Photosynthesis". Hans Journal of Computational Biology 08, n. 01 (2018): 1–7. http://dx.doi.org/10.12677/hjcb.2018.81001.
Testo completo
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Qin, Xiaojie, Deke Xing, Yanyou Wu, Weixu Wang, Meiqing Li e Kashif Solangi. "Diurnal Variation in Transport and Use of Intracellular Leaf Water and Related Photosynthesis in Three Karst Plants". Agronomy 12, n. 11 (6 novembre 2022): 2758. http://dx.doi.org/10.3390/agronomy12112758.
Testo completoAbstract (sommario):
Except for transpired water, the intracellular water stored in leaves accounts for only 1–3% of the water absorbed by roots. Understanding water transport and use, as well as the related photosynthetic response, helps with determining plant water status and improving the revegetation efficiency in fragile karst habitats. In this study, we conducted experiments on 8 year old naturally growing plants of Coriaria nepalensis Wall., Broussonetia papyrifera (L.) Vent., and Elaeocarpus decipiens Hemsl. in karst areas. We determined the diurnal variations in leaf electrophysiology, water potential, gas exchange, and chlorophyll fluorescence parameters. The results indicated that C. nepalensis plants maintained a high photosynthetic rate, with a high root water uptake ability and leaf intracellular water-holding capacity (LIWHC). The stomata quickly closed to conserve water within cells and protect the photosynthetic structure. B. papyrifera maintained stable intracellular water transport rate (LIWTR), and the photosynthetic efficiency was increased with increasing intracellular water-use efficiency (LIWUE). B. papyrifera also maintained its photosynthesis by efficiently using the transpired water when the LIWHC was increased. The inter- and intracellular water in the leaves of E. decipiens remained stable, which could be attributed to the leathery leaves and its high water-holding capacity. The photosynthesis of E. decipiens was low and stable. Compared with the high photosynthesis, high transpiration, and low instantaneous water-use efficiency (WUEi) pattern in C. nepalensis plants, E. decipiens plants exhibited low photosynthesis, low transpiration, and low WUEi, whereas B. papyrifera plants presented high photosynthesis, low transpiration, and high WUEi. Plants in karst regions change their transport and use of intracellular leaf water to regulate the photosynthetic performance, which differs among different plant species.
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Greer, Dennis H. "Photosynthetic light responses of apple (Malus domestica) leaves in relation to leaf temperature, CO2 and leaf nitrogen on trees grown in orchard conditions". Functional Plant Biology 45, n. 11 (2018): 1149. http://dx.doi.org/10.1071/fp18093.
Testo completoAbstract (sommario):
Apple trees growing in orchard conditions with two levels of soil nitrogen were used to determine photosynthetic light responses in relation to leaf temperature. In addition, leaves growing along the shoot were measured, and substrate supply for photosynthesis manipulated by altering CO2 concentrations. Results indicated highly significant interactions between leaf temperature, CO2 concentration, leaf position and nitrogen concentrations on attributes of the photosynthetic light responses. Elevated CO2 enhanced the effect of leaf temperature on the light saturated rate (Amax). There were significant effects of leaf position, and apparent photon yield (quantum efficiency) of photosynthesis, Amax and photosynthetic nitrogen use efficiency (ANUE) increased along the shoot, from leaves at the shoot base to those at apical positions; elevated CO2 enhanced these differences. A similar trend occurred with leaf nitrogen, accounting for increases in the photon yield, Amax and ANUE. It was concluded that apical leaves may have accumulated nitrogen which caused the high photosynthetic capacity and nitrogen use efficiency, as these leaves were possibly most exposed. Basal leaves, being possibly exposed to lower light intensities, had low nitrogen concentrations which accounted for their low photosynthetic light responses. This study does demonstrate that the shoot position of the apple leaves had marked effects on the photosynthetic light response and these were correlated with the leaf nitrogen content.
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Cui, Xin, Huifang Cen, Cong Guan, Danyang Tian, Huayue Liu e Yunwei Zhang. "Photosynthesis capacity diversified by leaf structural and physiological regulation between upland and lowland switchgrass in different growth stages". Functional Plant Biology 47, n. 1 (2020): 38. http://dx.doi.org/10.1071/fp19086.
Testo completoAbstract (sommario):
Understanding and enhancing switchgrass (Panicum virgatum L.) photosynthesis will help to improve yield and quality for bio-industrial applications on cellulosic biofuel production. In the present study, leaf anatomical traits and physiological characteristics related to photosynthetic capacity of both lowland and upland switchgrass were recorded from four varieties across the vegetative, elongation and reproductive growth stages. Compared with the upland varieties, the lowland switchgrass showed 37–59, 22–64 and 27–73% higher performance on height, stem and leaf over all three growth stages. Leaf anatomical traits indicated that the leaves of lowland varieties provided more space for carbon assimilation and transportation caused by enhanced cell proliferation with more bundles sheath cells and larger contact areas between the bundle sheath and mesophyll cells (CAMB), which lead to the 32–72% higher photosynthetic capacity found in the lowland varieties during vegetative and elongation growth. However, photosynthetic capacity became 22–51% higher in the upland varieties during the reproductive stage, which is attributed to more photosynthetic pigment. In conclusion, lowland varieties gain a photosynthetic advantage with enhanced bundle sheath cell proliferation, while the upland varieties preserved more photosynthetic pigments. Our study provides new insights for improving the yield in crops by enhancing photosynthesis with anatomical and physiological strategies.
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Pokorný, J., J. Pulkrábek, P. Štranc e D. Bečka. "Photosynthetic activity of selected genotypes of hops (Humulus lupulus L.) in critical periods for yield formation". Plant, Soil and Environment 57, No. 6 (8 giugno 2011): 264–70. http://dx.doi.org/10.17221/30/2011-pse.
Testo completoAbstract (sommario):
This paper evaluates the influence of genotype on the photosynthetic activity of hops in the period critical for generating yield. Results over three years from measuring the photosynthesis rate statistically show an increase in the photosynthetic activity of hop plants in the flowering stage. The average photosynthetic rates from measurements on the second date (BBA 65) in the years 2007, 2008, and 2009 increased by 17.9%, 45.6%, and 49.2%, respectively. Different photosynthesis curve trends during the final stage of ontogenesis of the plants indicate the maturity level of each hop genotype. As regards the genotypes for which photosynthesis did not reduce significantly, it may be assumed that such plants had not reached technical maturity. The results from the three-year study also show that any promising genotype, with respect to the photosynthesis rate and yield, is the result of breeding of new varieties with greater resistance to drought and high temperatures. Very good results in photosynthetic activity were reached by the new varieties exhibiting high yield and a similar chemical composition to Saaz hop and those sharing the same origins to Saaz, showing a higher content of bitter substances. In 2008 and 2009, all three new forms reached yield levels of 2.35 to 3.12 t/ha of dry hops.
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Hill, Judson P., e Matthew J. Germino. "Coordinated variation in ecophysiological properties among life stages and tissue types in an invasive perennial forb of semiarid shrub steppe". Canadian Journal of Botany 83, n. 11 (novembre 2005): 1488–95. http://dx.doi.org/10.1139/b05-116.
Testo completoAbstract (sommario):
Semiarid lands of North America are vulnerable to invasion by exotic forbs that frequently have an extended phenology compared with native herbaceous species. We hypothesized that photosynthetic stems, rosette leaves, and cauline leaves of Centaurea maculosa Lam. (knapweed) would differ in ecophysiological specialization and that these differences would enhance plant carbon uptake across seasonal variations in microclimate. Photosynthesis, water relations, and morphological features of C. maculosa were measured under natural variations in temperature and soil water, and under manipulated light environments, in adults compared with seedlings having only rosette leaves. Carbon gain was greater in adults than in seedlings owing to high photosynthesis in cauline and rosette leaves when water was abundant. Otherwise, photosynthesis was relatively lower but persistent through drought in all tissues and ages until senescence. Photosynthesis decreased with water stress in all tissues except stems. Stems comprised up to 36% of photosynthetic area following senescence of rosette leaves during seasonal drought. Seedlings expressed shade acclimation compared with rosette and especially cauline leaves of adults, although adult rosette leaves had flexible photosynthetic light responses. Contrasting ecophysiological specializations of photosynthetic tissues enhance carbon gain of adult C. maculosa as light, water, and temperature vary during its relatively long growth season.