Academic literature on the topic 'Vapour pressure deficit'
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Journal articles on the topic "Vapour pressure deficit"
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Liptay, A., C. S. Tan, R. Ramsey, C. F. Drury, D. W. A. Hunt, T. Jewett, S. Weaver, and L. Woodrow. "Low vapour pressure deficits: Historical frequency and effect on tomato yield in southwestern Ontario." Canadian Journal of Plant Science 78, no. 3 (July 1, 1998): 473–75. http://dx.doi.org/10.4141/p97-121.
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An historical analysis of vapour pressure deficit was done to determine the frequency of very low vapour pressure deficits during June, July and August of the growing seasons, in Harrow, Ontario. The impetus for the analysis was a lack of yield response of processing tomatoes to fertigation in 1995 compared to other years or sites. In the historical analysis, 2 years, 1964 and 1995, were identified as having a high frequency of very low daily vapour pressure deficits during the growing season. The site of the experiment where low VPD was recorded was about 5 km north from the shore of Lake Erie. A site 27 km away from Harrow, and about 10 km north of Lake Erie, near Leamington, Ontario, had a normal, increased yield response to the fertigation treatment. Key words: Relative humidity, vapour pressure deficit, yield, tomato
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Kumari, Santosh, and H. M. Rawson H. M. Rawson. "Temperature, Vapour Pressure Deficit and Water Stress Interaction on Transpiration in Wheat." International Journal of Scientific Research 2, no. 3 (June 1, 2012): 375–76. http://dx.doi.org/10.15373/22778179/mar2013/123.
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Grossnickle, Steven C., and John H. Russell. "Gas exchange processes of yellow-cedar (Chamaecyparis nootkatensis) in response to environmental variables." Canadian Journal of Botany 69, no. 12 (December 1, 1991): 2684–91. http://dx.doi.org/10.1139/b91-337.
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Yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach) gas exchange processes were measured in response to the following primary environmental variables: photosynthetically active radiation, vapour pressure deficit, root temperature, and soil moisture. Under nonlimiting edaphic conditions, maximum stomatal conductance and maximum CO2 assimilation increased rapidly as photosynthetically active radiation increased from 0 to 200 μmol∙m−2∙s−1 and from 0 to 500 μmol∙m−2∙s−1, respectively. Thereafter, greater photosynthetically active radiation levels only resulted in minor increases in stomatal conductance and CO2 assimilation. Maximum stomatal conductance and maximum CO2 assimilation declined in a concave manner as vapour pressure deficit increased from 1 to 5 kPa. Response surface model for stomatal conductance showed vapour pressure deficit was the primary influence after light had caused initial stomatal opening. Response surface modeling approach showed CO2 assimilation increased as photosynthetically active radiation increased, but increased vapour pressure deficit resulted in a suppression of CO2 assimilation. Response surface model showed internal CO2 concentration declined sharply as photosynthetically active radiation increased from 0 to 500 μmol∙m−2∙s−1, but it remained constant with increasing vapour pressure deficit. Decreasing root temperature resulted in a continual decline in CO2 assimilation and stomatal conductance from 22 to 1 °C, while internal CO2 concentration declined from 22 to 13 °C with little change between 13 and 1 °C. As predawn shoot water potential decreased from −0.5 to −2.0 MPa, CO2 assimilation declined in a linear manner, while stomatal conductance and internal CO2 concentration declined in a concave manner. Key words: Chamaecyparis nootkatensis, CO2 assimilation, stomatal conductance, internal CO2 concentration, photosynthetically active radiation, vapour pressure deficit, root temperature, predawn shoot water potential.
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Lentzou, D., G. Xanthopoulos, C. Templalexis, and A. Kaltsa. "The transpiration and respiration as mechanisms of water loss in cold storage of figs." Food Research 5, no. 6 (December 5, 2021): 109–18. http://dx.doi.org/10.26656/fr.2017.5(6).178.
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Transpiration and respiration are two mechanisms of water loss in fresh agricultural products, resulting in visual and texture degradation. Neglecting respiration as a mechanism of water loss may lead to erroneous results at saturation where water vapour pressure deficit is zero and thus water loss is expected to be zero, however, the existence of a finite water loss is noted. In this context, an analysis of the associated with transpiration and respiration water loss in figs (Ficus carica L.) was carried out at 0oC, 10oC and 20oC and 45.64%, 80.22% and 98.65% relative humidity as well as the air conditions of walk-in cold storage rooms. The estimated transpiration rate ranged between 0.11-1.416 mg cm-2 h -1 for a water vapour pressure deficit of 0.0-0.98 kPa. The water vapour pressure deficit estimation was based on the difference between cold air temperature and figs’ surface temperature. The respiration rate was calculated at 0oC, 10oC and 20oC as 0.47±0.08, 0.94±0.11 and 2.69±0.17 mLCO2100g-1 h -1 . Quantification of the water loss showed that at 20oC and saturation, the water loss due to respiration accounts for 3.9% of the respective water loss due to water vapour pressure deficit while on average, the water loss due to respiration accounts for 1.5%, 2.1% and 2.6% of the water loss due to water vapour pressure deficit at 0oC, 10oC and 20oC.
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Wibig, Joanna, and Ewelina Krawczyk. "Zmiany wilgotności powietrza w Łodzi w latach 1966–2020 w świetle wybranych wskaźników." Prace Geograficzne, no. 170 (March 2023): 119–41. http://dx.doi.org/10.4467/20833113pg.23.002.17490.
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The aim of the study is to present changes in air humidity in central Poland in the years 1966–2000 in Łódź as an example. The values of air temperature, relative humidity and atmospheric pressure from four observation terms, 00, 06, 12 and 18 UTC, were used. On this basis, the saturated vapour pressure, the current vapour pressure, and the saturation deficit were calculated. Then, the variability of these three indicators and relative humidity was examined. The variability of monthly and seasonal average values of humidity indices in four observation periods was presented, the trends in seasonal variability of humidity indices were calculated and the distribution functions of their distributions were compared in the midday period in three 15-year periods: 1966–1980, 1986–2000 and 2006–2020. It has been shown that the pressure of saturated water vapour is the highest in summer, the lowest in winter, and slightly higher in spring than in autumn at all times, except for the night. It increased significantly in the studied period as a result of the increase in air temperature. A comparison of the distributions in three 15-year periods shows a significant increase in the probability of occurrence of high values of saturation vapour pressure, even above 30hPa. The water vapour pressure in the air is highest in summer and lowest in winter, but in spring it is lower than in autumn. All trend coefficients are positive, but only less than half are statistically significant. A comparison of the distributions over three 15-year periods show a slight increase in the probability of higher values of the actual vapour pressure. The saturation deficit, as the difference between the previous two indicators, increases significantly. Its value in spring is significantly higher than in autumn. The trend is positive, especially in spring and summer, and the comparison of distributions shows that in the last 15 years the probability of high values of saturation deficit increased significantly. The course of relative humidity is the opposite of saturation deficit. In autumn, the relative humidity is definitely higher than in spring. The trend is down. To sum up, warming brings an increase in the capacity of the atmosphere for water vapour, a slight increase in the amount of water vapour in the air, but also a significant increase in saturation deficit and a decrease in relative humidity, which is particularly strong in spring in the first half of the growing season.
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Chandiposha, Misheck, Godfrey E. Zharare, and Muntubani D. S. Nzima. "Screening of Sugarcane Varieties for Tolerance to Water Deficiency Using Containers." International Journal of Agronomy 2023 (August 23, 2023): 1–10. http://dx.doi.org/10.1155/2023/5705785.
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The negative effects of water deficiency in sugarcane production caused by climate change on the productivity of sugarcane can be mitigated by drought tolerant varieties. A 14 × 2 factorial arrangement in completely randomised design replicated three times was used to screen 14 varieties for drought tolerance at the Zimbabwe Sugar Experiment Station (ZSAES). The first factor was the sugarcane varieties viz ZN1, ZN2, ZN3, ZN4, ZN5, ZN6, ZN7, ZN8, ZN9, ZN10, CP72–1312, NCo376, N14, and CP72–2086. The second factor comprised of two levels of irrigation, namely, well-watered (100% by volume) and water-deficit stressed (30% by volume). The parameters measured in this study which included tiller count, leaf SPAD index, total plant dry mass, photosynthetic rate, and leaf temperature were found not suitable for screening sugarcane for tolerance to water-deficit stress. Water-deficit stressed varieties ZN1, ZN8, ZN10, and N14 had the tallest stalks. Varieties CP72–2086, ZN2, ZN5, CP72–1312, ZN4, ZN6, and ZN9 were stunted, indicating that they were probably drought-sensitive. Leaf vapour pressure deficits of varieties ZN8, ZN10 and N14 were higher in water-stressed plants than in the well-watered ones. The vapour pressure deficit of well-watered NCo376 plants was higher than that of water-stressed plants. Furthermore, the stomatal conductance of water-stressed NCo376 plants was greater than that of the other varieties tested, showing more tolerance to drought. Based on stem height, stomatal conductance, vapour pressure deficit, transpiration rate and dry matter parameters measured in the present study, sugarcane varieties that are recommended to cane farmers in Zimbabwe when faced with drought are NCo376, ZN1, ZN8, ZN10 and ZN14.
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Bacher, Harel, Yoav Sharaby, Harkamal Walia, and Zvi Peleg. "Modifying root-to-shoot ratio improves root water influxes in wheat under drought stress." Journal of Experimental Botany 73, no. 5 (November 16, 2021): 1643–54. http://dx.doi.org/10.1093/jxb/erab500.
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Abstract Drought intensity as experienced by plants depends upon soil moisture status and atmospheric variables such as temperature, radiation, and air vapour pressure deficit. Although the role of shoot architecture with these edaphic and atmospheric factors is well characterized, the extent to which shoot and root dynamic interactions as a continuum are controlled by genotypic variation is less well known. Here, we targeted these interactions using a wild emmer wheat introgression line (IL20) with a distinct drought-induced shift in the shoot-to-root ratio and its drought-sensitive recurrent parent Svevo. Using a gravimetric platform, we show that IL20 maintained higher root water influx and gas exchange under drought stress, which supported a greater growth. Interestingly, the advantage of IL20 in root water influx and transpiration was expressed earlier during the daily diurnal cycle under lower vapour pressure deficit and therefore supported higher transpiration efficiency. Application of a structural equation model indicates that under drought, vapour pressure deficit and radiation are antagonistic to transpiration rate, whereas the root water influx operates as a feedback for the higher atmospheric responsiveness of leaves. Collectively, our results suggest that a drought-induced shift in root-to-shoot ratio can improve plant water uptake potential in a short preferable time window during early morning when vapour pressure deficit is low and the light intensity is not a limiting factor for assimilation.
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Medrano, E., M. C. Sánchez-Guerrero, and P. Lorenzo. "INFLUENCE OF VAPOUR PRESSURE DEFICIT ON TOMATO CROP TRANSPIRATION." Acta Horticulturae, no. 614 (September 2003): 613–18. http://dx.doi.org/10.17660/actahortic.2003.614.91.
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Conaty, Warren C., James R. Mahan, James E. Neilsen, and Greg A. Constable. "Vapour pressure deficit aids the interpretation of cotton canopy temperature response to water deficit." Functional Plant Biology 41, no. 5 (2014): 535. http://dx.doi.org/10.1071/fp13223.
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Crop canopy temperature (Tc) is coupled with transpiration, which is a function of soil and atmospheric conditions and plant water status. Thus, Tc has been identified as a real-time, plant-based tool for crop water stress detection. Such plant-based methods theoretically integrate the water status of both the plant and its environment. However, previous studies have highlighted the limitations and difficulty of interpreting the Tc response to plant and soil water stress. This study investigates the links between cotton Tc, established measures of plant water relations and atmospheric vapour pressure deficit (VPDa). Concurrent measures of carbon assimilation (A), stomatal conductance (gs), leaf water potential (Ψl), soil water (fraction of transpirable soil water (FTSW)) and Tc were conducted in surface drip irrigated cotton over two growing seasons. Associations between A, gs, Ψl, FTSW and Tc are presented, which are significantly improved with the inclusion of VPDa. It was concluded that utilising the strong associations between Ψl, VPDa and Tc, an adjustment of 1.8°C for each unit of VPDa should be made to the critical Tc for irrigation. This will improve the precision of irrigation in Tc based irrigation scheduling protocols. Improved accuracy in water stress detection with Tc, and an understanding of the interaction the environment plays in this response, can potentially improve the efficiency of irrigation.
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Gholipoor, M., S. Choudhary, T. R. Sinclair, C. D. Messina, and M. Cooper. "Transpiration Response of Maize Hybrids to Atmospheric Vapour Pressure Deficit." Journal of Agronomy and Crop Science 199, no. 3 (December 7, 2012): 155–60. http://dx.doi.org/10.1111/jac.12010.
Full textDissertations / Theses on the topic "Vapour pressure deficit"
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Wahid, Zabri Abdul. "The effect of low vapour pressure deficit (VPD) on growth of sweet pepper (Capsicum annuum L.)." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267941.
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Prayag, Kervin D. "The effects of elevated [CO₂] and decreased vapour pressure deficit on the nutrient status of maize and wheat plants under well-watered conditions." Master's thesis, University of Cape Town, 2020. http://hdl.handle.net/11427/32525.
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Increases in photosynthetic rates (A), biomass production and grain yield have been measured across a range of C₃ plants under elevated atmospheric [CO₂] ('eCO₂'). However, decreases in the nutritional status of many C₃ plants growing at eCO₂ often occur concurrently with these increases. Several mechanisms have been proposed for these eCO₂-induced decreases, such as dilution effects due to enhanced carbohydrate production, down-regulation of photosynthesis, reduced root development, and decreased transpiration-driven mass flow delivery of nutrients. Reduced mass flow at eCO₂ is generally accepted as one cause for altered nutrient status in C₃ plants. However, eCO₂-induced reductions in mass flow remain understudied in C₄ plants, even though they account for about 18% of the total global net primary productivity and represent a large food source globally (e.g. maize and sorghum). This thesis investigated how mass flow reductions affect the nutrient status of wheat (C₃) and maize (C₄) plants. Reduced mass flow in both maize and wheat plants was induced with eCO₂ and by varying leaf-to-air vapour pressure deficits (VPD). I hypothesised that reduced mass flow at eCO₂ and at low VPD will negatively affect nutrient status in both the C₃ (wheat) and the C₄ (maize) species. In the first experiment, maize and wheat plants were grown at 400 and 800 ppm [CO₂], in three well-watered soils, ranging from sandy to clayey, with and without fertilisation. In the second experiment, plants were grown at three VPD levels, namely 1.613 kPa, 0.773 kPa and 0.350 kPa, in well-watered soil and sand. In the latter experiment, to demonstrate the importance of mass flow, plants grown in sand were supplied nutrients in such a way that they had to rely exclusively on mass flow or diffusive processes (i.e. limited interception) for nutrient delivery to their rhizosphere. eCO₂ stimulated A on average by 22% in maize and by 50% in wheat, while stomatal conductance (ɡₛ) and cumulative water loss (CWL) were respectively decreased by 35% and 31% in maize, and by 26% and 37% in wheat. eCO₂ reduced mass flow delivery of most nutrients on average by 32% in maize, and by 38% in wheat. The hypothesis that eCO₂-induced reductions in mass flow negatively affect nutrient status in maize 33 and wheat was however not supported. This was attributed to the well-watered conditions of the soils, which may have allowed for other processes (e.g. diffusion) to make up for the mass flow reductions. From 0.773 kPa to 0.350 kPa VPD, CWL was decreased on average by 14% and 20% in the maize and wheat plants, respectively. A and ɡₛ were little affected by VPD, but plants of both species always accumulated more biomass at 0.773 kPa. Consequently, there was little evidence to suggest that VPD-induced reductions in mass flow negatively affect nutrient status in maize and wheat. Reduced CWL may have impeded root-to-shoot transport of ions and reduced dry biomass accumulation in the maize and wheat plants at 0.350 kPa (-40% and -22% on average respectively, relative to 0.773 kPa plants). Tissue [NPK] was also decreased (-13%, -41% and -47% respectively) in the 0.350 kPa VPD sand wheat plants, while increases in the proportion of finer roots may have alleviated effects of reduced CWL on tissue [NPK] in the C₄ species. The findings from both experiments imply a decrease in the importance of mass flow for the delivery of nutrients to the rhizosphere under well-watered conditions. However, reductions in mass flow to a similar extent in both species at eCO₂ and low VPD - measured in the present study - suggest that under conditions of low water and nutrient availability, tissue nutrient concentrations could be negatively affected when transpiration is reduced.
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Carneiro, Rafaela Lorenzato. "Caracterização da capacidade fotossintética e da condutância estomática em árvores de Pinus caribaea var. hondurensis e de Pinus taeda em Itatinga, São Paulo." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-10092013-170745/.
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Realizaram-se campanhas em árvores de cinco anos de idade de Pinus caribaea var. hondurensis e Pinus taeda em parcelas controle (sem fertilização e sem irrigação) e parcelas fertilizadas e irrigadas, durante o verão e o inverno de 2012 visando caracterizar as seguintes variáveis fisiológicas: i) Capacidade máxima fotossintética (Amax); ii) Fotossíntese ao longo do dia (A); iii) Variação da condutância estomática (gs) em relação ao aumento do déficit de pressão de vapor (DPV); e iv) Taxas máximas de carboxilização (Vcmax) e de transporte de elétrons (Jmax) via curvas A/Ci. O estudo foi realizado no projeto Produtividade Potencial do Pinus no Brasil, localizado na Estação Experimental da ESALQ/USP em Itatinga-SP.Foram escolhidas três árvores médias por parcela para as avaliações fisiológicas, realizadas com o LiCor 6400XT. A mensuração da Amax foi realizada no terço médio da copa, em dois galhos por árvore e em duas posições por galho, sendo realizada das 8 às 10 horas, e o comportamento da A, gs com o aumento do DPV, ocorreram de hora em hora, das 11 às 15 horas. Ao final, as acículas foram coletadas para a determinação da área foliar específica (AFE) e do nitrogênio foliar. As curvas A/Ci foram realizadas nas três árvores, um galho por árvore e duas posições por galho, entre 8 e 12 horas. Aos cinco anos o Pinus caribaea var. hondurensis apresenta o dobro do volume de madeira do que o Pinus taeda. As duas avaliações fisiológicas mostraram valores similares entre tratamentos, para cada espécie. Os valores de Amax foram maiores durante o verão e o Pinus caribaea var. hondurensis mostrou grande sensibilidade, comparativamente ao Pinus taeda. Ao analisar os dados de A e gs ao longo do dia, observa-se também maiores variações do Pinus caribaea var. honduresis. Os valores médios de Amax para o verão e o inverno foram 8,2 e 4,8 ?mol m-2 s-1 e 6,8 e 6,3 ?mol m-2 s-1 para o Pinus caribaea var. hondurensis e o Pinus taeda, respectivamente. Ocorreu redução dos valores de A e gs com o aumento do DPV, para ambas as campanhas em relação ao Pinus caribaea var. hondurensis e somente no inverno para o Pinus taeda. As duas espécies apresentaram relação positiva entre fotossíntese e transpiração, sendo que o Pinus caribaea var. hondurensis apresenta maior eficiência no uso da água. As médias da AFE e nitrogênio foliar foram de 9,6 m²kg-1, 10,1g Kg-1 e 10,0 m²kg-1, 13,4g Kg-1, para o Pinus caribaea var. hondurensis e Pinus taeda, respectivamente. Em relação aos parâmetros fotossintéticos o Pinus taeda se destacou em ambas as campanhas, com valores médios de Vcmax e Jmax maiores que o Pinus caribaea var. hondurensis, relacionado à maiores concentrações de nitrogênio foliar. Não houve relação entre o crescimento em biomassa das árvores e as medições da fotossíntese a nível foliar, indicando que outros processos a nível de copa, uso e alocação de fotossintetizados devem ser investigados para explicar a diferença de crescimento.The campaigns were conducted in trees with five years old of Pinus caribaea var. hondurensis and Pinus taeda in control plots (no fertilization and no irrigation) and fertilized and irrigated plots during summer and winter of 2012 to characterize the physiological variables: i) maximum photosynthetic capacity (Amax), ii) Photosynthesis throughout the day (A); iii) Changes in stomatal conductance (gs) in relation to the increase in vapor pressure deficit (VPD), and iv) Maximum rates of carboxilization (Vcmax) and maximum rates of electron transport (Jmax) based on A/Ci curves. The study was conducted in the project Potential Productivity of Pinus in Brazil, located at the Experimental Station of ESALQ/USP in Itatinga-SP. Three average trees per plot were chosen for physiological evaluations, performed with the LiCor 6400XT. The Amax measurement was performed in the middle third of the crown, in two branches per tree and two positions per branch, taken from 8 to 10am. To get the response of A and gs with increasing VPD, the measurements continued every hour, from 11 am to 3 pm. At the end of the measurements, the needles were collected for determination of specific leaf area (SLA) and leaf nitrogen (N). The A/Ci curves were performed in three trees, one branch per tree and two positions per branch were taken from 8 am to 12 pm. At five years, the Pinus caribaea var. hondurensis showed two-fold the wood volume of Pinus taeda. Both physiological measurements showed similar results between treatments for each species. Amax values were higher during summer, and Pinus caribaea var. hondurensis shower greater sensitivity compared to Pinus taeda. A and gs throughout the day showed higher variation in Pinus caribaea var. hondurensis. The average values of Amax for summer and winter were 8.2, 4.8 ?mol m-2 s-1 and 6.75, 6.3 ?mol m-2 s-1 for Pinus caribaea var. hondurensis and Pinus taeda, respectively. There was a reduction of A and gs with the increasing of DPV, for both campaigns for the Pinus caribaea var. hondurensis and only in winter campaign for Pinus taeda. Thus, the two species have different behaviors in response to climatic changes. The two species showed a positive relationship between photosynthesis and transpiration, with Pinus caribaea var. hondurensis showing greater water use efficiency. The average SLA and needle nitrogen were 9.6 m² kg-1, 10.1g kg-1 and 10 m² kg-1, 13.4g kg-1 for Pinus caribaea var. hondurensis and Pinus taeda, respectively. Photosynthetic parameters in Pinus taeda was higher in both campaigns, with average values of Vcmax and Jmax greater than in Pinus caribaea var. hondurensis, related to higher concentration of needle nitrogen. There was no relationship between tree biomass growth and leaf-level measurements of photosynthesis, indicating that other processes at crown level, use and allocation of photosynthates should be investigated to explain the difference in growth.
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Pilloni, Raphael. "AGRONOMICAL AND PHYSIOLOGICAL STUDY OF THE RESPONSE OF SORGHUM AND PEARL MILLET CROPS TO HIGHER SOWING DENSITY IN THE SEMI-ARID TROPICS. ASSESSEMNT OF THE OPPORTUNITY FOR SUSTAINABLE INTENSIFICATION AND CONSEQUENCE FOR THE TRANSPIRATION RESPONSE TO EVAPORATIVE DEMAND OF THE CROPS." Electronic Thesis or Diss., Université de Montpellier (2022-....), 2022. http://www.theses.fr/2022UMONG051.
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Dans les régions tropicales semi-arides, le sorgho et le mil sont des sources essentielles de revenus et de calories. Une intensification durable est donc nécessaire pour assurer la sécurité alimentaire. Ces deux céréales sont en grande partie cultivées dans des systèmes de petites exploitations et cultivées à faible densité, ce qui ouvre la voie à une augmentation du rendement grâce à cette gestion agronomique. A travers des essais au champ et des essais lysimétriques réalisés en Inde et au Sénégal, ce travail a montré la possibilité d'augmenter significativement la biomasse et le rendement en grain des deux espèces, avec le même régime d'irrigation et la même fertilisation. Nous avons mis en évidence une diminution du déficit de pression de vapeur (VPD) dans les canopées de haute densité, résultant en une augmentation de l'efficacité d'utilisation de l'eau des cultures. Alors que les deux cultures ont répondu positivement à l'augmentation de la densité, il y avait également de grandes différences entre les espèces dans la variation génotypique de la réponse à la densité, à savoir une forte interaction génotype x densité dans le sorgho pour la biomasse et la WUE, mais aucune dans le millet perlé. La variation génotypique dans le degré de réponse pour WUE trouvée chez le sorgho et son lien avec l'accumulation de biomasse ont conduit à étudier les différences putatives dans la réponse de transpiration des cultures à la demande evaporative. Nous avons testé cette hypothèse en plein air avec des plants de sorgho cultivés en canopée dans des expériences en champ et en lysimètre. La réponse de l'évapotranspiration a été mesurée en fonction de la demande evaporative. Cette réponse était linéaire et, avec le WUE, a montré une grande variation génétique. Le WUE était étonnamment plus élevé dans les génotypes avec la réponse de transpiration la plus élevée à la demande evaporative (Penman-Monteith). Ces génotypes étaient également ceux qui permettaient une pénétration maximale de la lumière dans la canopée. Ce travail ouvre la porte à l'intensification, à court terme en augmentant la densité de semis dans les zones sèches en utilisant des cultivars de sorgho et de millet perlé qui montrent une forte réponse à la densité, et à moyen terme en sélectionnant des cultivars de sorgho adaptés à une densité élevéeIn the semi-arid tropics, sorghum and pearl millet or key source of income and calories. Sustainable intensification is therefore needed to ensure food security. These two cereals are largely grown in smallholder farming system and cultivated at low density, opening an avenue to increase yield through this agronomic management. Through field and lysimetric trials carried out in India and Senegal this work showed the possibility to increase significantly, the biomass and grain yield in both species, with the same irrigation regime and fertilization. We highlighted a lowering of the vapour pressure deficit (VPD) in the canopies of high density, resulting in an increase in water use efficiency of the crops. While both crops responded positively to increased density, there were also large specie differences in the genotypic variation of the response to density, namely a strong genotype x density interaction in sorghum for biomass and WUE, but none in pearl millet. The genotypic variation in the degree of WUE response found in sorghum and its link with biomass accumulation led to investigate putative differences in the transpiration response of the crops to the evaporative demand. We tested this hypothesis outdoors with canopy-grown sorghum plants in field and lysimeter experiments. The response of the evapotranspiration was measured against the evaporative demand. This response was linear and, with WUE, showed large genetic variation. WUE was surprisingly higher in genotypes with the highest transpiration response to the evaporative demand (Penman-Monteith). These genotypes were also those that allowed maximum light penetration into the canopy. This work opens the door to intensification, in the short term by increasing sowing density in drylands using sorghum and pearl millet cultivars that show a strong response to density, and in the medium term by selecting sorghum cultivars adapted to high density
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DePauli, Arianne. "Small Scale Vapor Pressure Deficit Changes Influence on Transpiration." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/613834.
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Adelman, Jonathan D. "Using temporal patterns in vapor pressure deficit to explain spatial autocorrelation dynamics in tree transpiration." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1313909961&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Affeld, Kathrin. "Spatial complexity and microclimatic responses of epiphyte communities and their invertebrate fauna in the canopy of northern rata (Metrosideros robusta A. Cunn.: Myrtaceae) on the West Coast of the South Island, New Zealand." Diss., Lincoln University, 2008. http://hdl.handle.net/10182/771.
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Rain forest canopies are renowned for their very high biodiversity and the critical role they play in key ecological processes and their influence on global climate. Despite that New Zealand supports one of the most diverse and extensive epiphyte flora of any temperate forest system, few studies have investigated epiphyte communities and their invertebrate fauna along with factors that influence their distribution and composition. This thesis represents the first comprehensive study of entire epiphyte communities and their resident invertebrate fauna in the canopy of New Zealand’s indigenous forests. The aim of this study was to determine spatial patterns of epiphyte and invertebrate species richness, abundance and community composition in relation to abiotic variables, and in particular, the responses of these communities to elevated temperature and rainfall. This study was carried out in coastal lowland podocarp-broadleaved forests at two sites on the West Coast of the South Island of New Zealand. Samples from 120 mat-forming epiphyte assemblages located on inner canopy branches of 40 northern rata (Metrosideros robusta) trees were studied to characterise the component flora and fauna. Additionally, biomass, branch and tree characteristics and community responses to treatments designed to elevate temperature and rainfall to simulate predicted climate change were measured. This investigation revealed astonishing diversity and functional complexity of epiphyte and invertebrate life in this ecosystem. The 30.6 kg (dry weight) of epiphyte material collected contained a total of 567 species, 170 epiphyte and 397 invertebrate (excluding immature specimens and mites) species, including at least 10 species new to science and many undescribed species Epiphyte communities were found to be dominated by non-vascular plants (80 % of the total species richness), particularly liverworts and invertebrate communities were dominated with respect to abundance (~ 80 % of the total individuals) by Acari, Collembola and Hymenoptera (primarily ants) and functionally by scavengers and ants. Epiphyte and invertebrate communities were highly variable with respect to spatial patterning of species richness, abundance and composition across sites, among trees within sites and among branches within trees. Overall, a highly significant proportion, > 75 %, of the variance could be attributed to differences at the branch level, but these differences could not be explained by the environmental factors measured. There were no consistent relationships between the spatial pattern of epiphytes and invertebrates, or between vascular and non-vascular plants. However, there were significant positive correlations between epiphyte biomass and invertebrate species richness (r = 0.472; p < 0.0001) and abundance (r = -0.395; p < 0.0001), as well as non-living epiphyte biomass and scavenger species richness (r = 0.4; p < 0.0001). Microclimatic measurements taken on epiphyte mats were also highly variable with respect to temperature and relative humidity at similar physical locations within the same tree as well as across trees within sites. There was also considerable variation in the intensity and frequency of climatic extremes, although potentially harmful climatic conditions were experienced by all the epiphyte mats for which weather variables were measured. Negative correlations existed between both epiphyte and invertebrate community composition and increased temperatures expressed as cumulative degree days above 5˚C. However, variability was such that there was no direct evidence that increased temperature and rainfall treatments had an effect on invertebrate species richness, abundance or diversity. Northern rata host trees harbour an astonishingly diverse and complex canopy flora and fauna that is characterised by high spatial variability. Such variability highlights that to determine species distribution and community dynamics in canopy habitats in response to disturbance caused either by climate change or invasive species the structure of entire communities at different taxonomic and spatial scales, along with their responses to microclimatic factors, need to be studied. If such complexities are not taken into account, inappropriate interpretation may result in poor decisions concerning the conservation status, vulnerability and subsequent management of such unique ecosystems.
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Renda, da Costa Paula MR. "A Quantified Approach to Tomato Plant Growth Status for Greenhouse Production in a Semi Arid Climate." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194440.
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Balancing plant growth between vegetative and reproductive status is crucial for producing high quality greenhouse tomatoes while maintaining high productivity in long crop production seasons. In the tomato industry, certain plant morphological characteristics are used to classify plant growth status as vegetative, reproductive or balanced. Each growth status has been associated with distinct greenhouse environments which reduce or enhance transpiration.The effect of different transpiration on vegetative, reproductive or balanced plant growth status as defined by a set of plant morphological characteristics was investigated. To validate the practical significance of such classification, growth status was quantified as the relationship between variations in morphological characteristics and the fresh weight distributed between reproductive and vegetative organs.Two electrical conductivity (EC) levels of the nutrient solution, high and standard EC, were combined with two potential transpiration environments, low and high potential transpiration. All treatment combinations were contrasted with a reference greenhouse environment similar to the industry standard.Electrical conductivity had the greatest effect on morphological characteristics which were reduced in size with high EC. For each EC level, the response decreased for increasing potential transpiration. Stem diameter had the greatest sensitivity to the different treatment combinations. For the standard EC and for the range of potential transpirations achieved, stem diameter varied within a relatively narrow range, close to the industry standard 'threshold' used to classify a balanced tomato plant. A reproductive plant growth status, as evaluated by a smaller value than this threshold, was observed only with high EC. No vegetative plants were produced within any potential transpiration or EC treatment combination.High EC decreased the cumulative total fresh weight production by the same magnitude for all potential transpirations. Potential transpiration had a minimal effect on the total fresh weight production or on its components. As a result, the fresh weight ratio between reproductive and vegetative plant organs was similar for most potential transpiration environments, regardless of variations in stem diameter. Therefore, within the range of potential transpiration environments achieved, the distinction between vegetative and reproductive growth status as an indicator of fresh weight distribution and fruit yields could not be quantitatively validated.
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Raczka, B., S. C. Biraud, J. R. Ehleringer, C. T. Lai, J. B. Miller, D. E. Pataki, S. R. Saleska, et al. "Does vapor pressure deficit drive the seasonality of δ 13C of the net land-atmosphere CO2 exchange across the United States?" AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/625792.
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The seasonal pattern of the carbon isotope content (delta C-13) of atmospheric CO2 depends on local and nonlocal land-atmosphere exchange and atmospheric transport. Previous studies suggested that the delta C-13 of the net land-atmosphere CO2 flux (delta(source)) varies seasonally as stomatal conductance of plants responds to vapor pressure deficit of air (VPD). We studied the variation of (source) at seven sites across the United States representing forests, grasslands, and an urban center. Using a two-part mixing model, we calculated the seasonal delta(source) for each site after removing background influence and, when possible, removing delta C-13 variation of nonlocal sources. Compared to previous analyses, we found a reduced seasonal (March-September) variation in delta(source) at the forest sites (0.5 parts per thousand variation). We did not find a consistent seasonal relationship between VPD and delta(source) across forest (or other) sites, providing evidence that stomatal response to VPD was not the cause of the global, coherent seasonal pattern in (source). In contrast to the forest sites, grassland and urban sites had a larger seasonal variation in (source) (5) dominated by seasonal transitions in C-3/C-4 grass productivity and in fossil fuel emissions, respectively. Our findings were sensitive to the location used to account for atmospheric background variation within the mixing model method that determined (source). Special consideration should be given to background location depending on whether the intent is to understand site level dynamics or regional scale impacts of land-atmosphere exchange. The seasonal amplitude in delta C-13 of land-atmosphere CO2 exchange (delta(source)) varied across land cover types and was not driven by seasonal changes in vapor pressure deficit. The largest seasonal amplitudes of delta(source) were at grassland and urban sites, driven by changes in C-3/C-4 grass productivity and fossil fuel emissions, respectively. Mixing model approaches may incorrectly calculate delta(source) when background atmospheric observations are remote and/or prone to anthropogenic influence.
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Szejner, Paul, William E. Wright, Flurin Babst, Soumaya Belmecheri, Valerie Trouet, Steven W. Leavitt, James R. Ehleringer, and Russell K. Monson. "Latitudinal gradients in tree ring stable carbon and oxygen isotopes reveal differential climate influences of the North American Monsoon System." AMER GEOPHYSICAL UNION, 2016. http://hdl.handle.net/10150/621424.
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The arrival of the North American Monsoon System (NAMS) terminates a presummer hyperarid period in the southwestern United States (U.S.), providing summer moisture that is favorable for forest growth. Montane forests in this region rely on winter snowpack to drive much of their growth; the extent to which they use NAMS moisture is uncertain. We addressed this by studying stable carbon and oxygen isotopes in earlywood and latewood from 11 sites along a latitudinal gradient extending from Arizona and New Mexico to Utah. This study provides the first regional perspective on the relative roles of winter versus summer precipitation as an ecophysiological resource. Here we present evidence that Ponderosa pine uses NAMS moisture differentially across this gradient. C-13/C-12 ratios suggest that photosynthetic water use efficiency during latewood formation is more sensitive to summer precipitation at the northern than at the southern sites. This is likely due to the fact that NAMS moisture provides sufficiently favorable conditions for tree photosynthesis and growth during most years in the southern sites, whereas the northern sites experience larger summer moisture variability, which in some years is limiting growth. Cellulose O-18 and C-13 values revealed that photoassimilates in the southern sites were produced under higher vapor pressure deficit conditions during spring compared to summer, demonstrating a previously underappreciated effect of seasonal differences in atmospheric humidity on tree ring isotope ratios. Our findings suggest that future changes in NAMS will potentially alter productivity and photosynthetic water use dynamics differentially along latitudinal gradients in southwestern U.S. montane forests.
Books on the topic "Vapour pressure deficit"
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Dat, James Frederick. Growth, water relations and nutrient uptake of bean seedlings under different air saturation vapour pressure deficit and nutrition regimes. Ottawa: National Library of Canada, 1994.
Find full textBook chapters on the topic "Vapour pressure deficit"
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Churakova, Olga V., Trevor J. Porter, Alexander V. Kirdyanov, Vladimir S. Myglan, Marina V. Fonti, and Eugene A. Vaganov. "Stable Isotopes in Tree Rings of Boreal Forests." In Stable Isotopes in Tree Rings, 581–603. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_20.
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AbstractThe boreal forests are widely expanded from subarctic forest to tundra, and from taigato forest-steppe zone (from 50 °N to 70 °N). We reviewed available stable isotope chronologies in tree-ring cellulose (δ13C, δ18O and δ2H) from 16 sites located in the Russian Federation; 4 research sites from Fennoscandia (Finland, Sweden and Norway); 5 sites from Canada, and 1 site from Alaska (USA) to evaluate impact of climatic changes from seasonal to annual scale across boreal forest ecosystems. Results of our review of carbon isotope data showed that droughtconditions (mainly high vapour pressure deficit) are prevalent for western and central regions of Eurasia, Alaska and Canada, while northeastern and eastern sites of Eurasian subarctic are showing water shortage developments resulting from decreasing precipitation. Oxygen isotopechronologies show increasing trends towards the end of the twentieth century mainly for all chronologies, except for the Siberian northern and southern sites. The application of the multiple stable isotope proxies (δ13C, δ18O, δ2H) is beneficial to study responses of boreal forests to climate change in temperature-limited environments. However, a deeper knowledge of hydrogen isotope fractionation processes at the tree-ring cellulose level is needed for a sound interpretation and application of δ2H for climate reconstructions, especially for the boreal forest zone where forest ecosystems are more sensitive to climatic and environmental changes.
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Sinclair, Thomas R. "Limited-Transpiration Rate Under Elevated Atmospheric Vapor Pressure Deficit." In Water-Conservation Traits to Increase Crop Yields in Water-deficit Environments, 11–16. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56321-3_3.
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Seyhan, Temuçin Göktürk, and Sinem Seyhan. "Fine-Tuning Growth Conditions: Leaf-Level Vapor Pressure Deficit Control for Optimized Photosynthesis." In Lecture Notes in Civil Engineering, 300–308. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-51579-8_27.
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Sultan, Muhammad, Hadeed Ashraf, Takahiko Miyazaki, Redmond R. Shamshiri, and Ibrahim A. Hameed. "Temperature and Humidity Control for the Next Generation Greenhouses: Overview of Desiccant and Evaporative Cooling Systems." In Next-Generation Greenhouses for Food Security. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97273.
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Temperature and humidity control are crucial in next generation greenhouses. Plants require optimum temperature/humidity and vapor pressure deficit conditions inside the greenhouse for optimum yield. In this regard, an air-conditioning system could provide the required conditions in harsh climatic regions. In this study, the authors have summarized their published work on different desiccant and evaporative cooling options for greenhouse air-conditioning. The direct, indirect, and Maisotsenko cycle evaporative cooling systems, and multi-stage evaporative cooling systems have been summarized in this study. Different desiccant materials i.e., silica-gels, activated carbons (powder and fiber), polymer sorbents, and metal organic frameworks have also been summarized in this study along with different desiccant air-conditioning options. However, different high-performance zeolites and molecular sieves are extensively studied in literature. The authors conclude that solar operated desiccant based evaporative cooling systems could be an alternate option for next generation greenhouse air-conditioning.
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Silva, Pedro, Miguel Carmo, João Rio, and Ilda Novo. "Evolution of the annual cycle of Burned Area in Portugal from 1980 to 2018: Implications for fire season management." In Advances in Forest Fire Research 2022, 1095–100. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_165.
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Wildfire activity in recent years not only have large total area burned but also large, single-day fire spread events that pose challenges to ecological systems and human communities. Our objective was to better understand the relationships between extreme single-day fire spread events, annual area burned, and fire-season climate, and predict changes under future warming. We employ a satellite-derived dataset of daily fire spread events in the western USA and gridded climate data over this region to assess relationships between extreme single-day fire spread events, annual area burned, and fire-season maximum temperature, climate moisture deficit, and vapor pressure deficit over a time period of 2002-2020. We then develop models to predict fire activity under a 2°C warming scenario. Extreme single-day fire spread events >1100 ha (the top 16%) accounted for 70% of the cumulative area burned over the period of analysis. Annual area burned was correlated with number and mean size of spread events, and those largest of these large fire spread events. In 2020, wildfires burned over 4 million ha in the US and we identified 441 extreme events in 2020 alone that together burned 2.2 million ha across our study area. In contrast, the average extreme events between 2002 and 2019 was 168 per year that burned 0.5 million ha. Fire season climate variables correlate strongly with the annual number of extreme events and area burned. Our models predict that the annual number of extreme fire spread events more than doubles under a 2°C warming scenario, with an attendant doubling in area burned. Exceptional fire seasons like 2020 will likely be more common, and wildfire activity under future extremes will likely exceed anything witnessed yet. Safeguarding human communities and supporting resilient ecosystems may require new lines of scientific inquiry, novel land management approaches, and accelerated climate mitigation efforts.
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Oliveira Brandão, Diego, Julia Arieira, and Carlos Afonso Nobre. "Threats and Sustainability of Brazil Nut (Bertholletia excelsa Bonpl.) Pre-Industrialization in the Amazon Region." In Sustainable Development. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.113715.
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Brazil nut (Bertholletia excelsa) is an important species in the Amazon, but the relationships between seed production and climate change are still poorly understood. Seed production data were obtained for the entire Brazilian Amazon, while data on precipitation, relative humidity, vapor pressure deficit, and temperature (mean and maximum) were collected to test their relationship with seed production in the Baixo Amazonas. Annual seed production in the Baixo Amazonas varied between 2156 and 10,235 tons per year from 1990 to 2021, with an average of 5192 tons per year. Linear regression analyses did not identify significant relationships between seed production and climatic variables during the same year (p > 0.05). However, significant relationships were found between the volume of seeds in the base year and climatic variables from 1 year before seed collection (p < 0.05), except for total precipitation (p = 0.15). Temperature was the main climatic variable affecting Brazil nut production, indicating that each 1°C increase in temperature is associated with an average decrease in seed volume ranging from 2595 to 2673 tons. Temperature measures explain between 38% and 42% of the variability in seed volume in the Baixo Amazonas. Therefore, it is crucial to mitigate global warming, invest in technological processes to add value to the remaining seeds, and adopt B. excelsa varieties more adapted to climate change.
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Oriakhi, Christopher O. "Liquids and Solids." In Chemistry in Quantitative Language. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780195367997.003.0016.
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The atoms or molecules in a liquid have enough kinetic energy to partially overcome the forces of attraction between them. Therefore, they are in constant random motion (as in a gas) but they are still relatively close together. However, they are not as tightly packed, or as well ordered, as in a solid. There is not as much free space in a liquid as in a gas. The atoms or molecules may aggregate together to form chains or rings that readily move relative to one another; this gives a liquid its fluid (flow) properties. Liquids generally occur as compounds. For example, water, ethanol, and carbon tetrachloride are liquids at room temperature. However, a few elements are also liquids at room temperature: bromine, cesium, gallium, mercury, and rubidium. A liquid is characterized by the following physical properties: boiling point and freezing point, density, compressibility, surface tension, and viscosity. These properties of a liquid are greatly influenced by the strength of its intermolecular forces. In summary: • Liquids have definite volume but no definite shape. They take on the shape of their containers. • Liquids are characterized by low compressibility, low rigidity, and high density relative to gases. • Liquids diffuse through other liquids. • Liquids can vaporize into the space above them and produce a vapor pressure. Polar molecules possess an electric dipole moment, μ, defined as the product of the magnitude of the partial charges Q+ and Q− on the molecule and the distance r separating the charges. In mathematical terms, it is given by the equation: μ = Qr The unit for μ is debyes (D), and 1 D = 3.336×10−30 coulomb meter (C-m). No interatomic bonds are completely ionic. Knowing the dipole moment of a compound, though, lets us differentiate ionic from covalent bonds by calculating the percent ionic character for the bonds. The percent ionic character of a bond is found by comparing the measured dipole moment of the molecule of the type A−B with the calculated dipole moment for the 100% ionized compound A+B−.
Conference papers on the topic "Vapour pressure deficit"
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Platt, C. M. R., S. A. Young, G. R. Patterson, and P. J. Manson. "Lidar and Radiometer Observations of Midlevel Clouds." In Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/orsa.1993.tuc.3.
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Midlevel clouds occur in the region of the troposphere, lying between high cirrus ice clouds and low boundary layer stratus, stratocumulus and cumulus clouds. Midlevel clouds are associated with moisture advected to the middle part of the troposphere between about 2km and 6km, or temperatures between about 0°C and -20°C. However, there is no sharp gradation between cirrus and altus clouds, rather, a blending of one into the other. Again, deep frontal clouds, which include midlevel cloud, can extend from cirrus level to the boundary layer. Both the depths and the compositions of midlevel clouds are thus very variable. The clouds can often exist as supercooled water drops, which sometimes glaciate rapidly; as the saturation vapour pressure over ice is lower than over water, and the deficit is maximum at about -15°C in the mid-troposphere, any tendency for ice crystals to form can cause rapid growth of the crystals at the expense of the water drops. Optical remote sensing of these clouds has been confined in the past to a few observations (e.g. Platt and Gambling, 1971, Platt and Bartusek, 1974, Platt, 1977, Sassen, 1984, Uchino et al., 1988). However, recently, a few more observations were made in the first FIRE experiment (e.g. Heymsfield et al., 1991) although observations tended to concentrate on cirrus.
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Broz, Adrian P., Gregory J. Retallack, Toby M. Maxwell, and Lucas C. R. Silva. "PALEOPROXY FOR VAPOR PRESSURE DEFICIT (VPD) FROM FOSSIL CELLULOSE AND PEDOGENIC CARBONATE." In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-317539.
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"Using light integrals and vapor pressure deficit to simulate irrigation scheduling for container nursery production." In 2015 ASABE / IA Irrigation Symposium: Emerging Technologies for Sustainable Irrigation - A Tribute to the Career of Terry Howell, Sr. Conference Proceedings. American Society of Agricultural and Biological Engineers, 2015. http://dx.doi.org/10.13031/irrig.20152147702.
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Chennaoui, Leila, Giovanni Cerri, and Sayyedbenyamin Alavi. "Turbomachinery-Based Vapor Pressure Amplifier for Refrigeration Energy Saving." In ASME 2017 Gas Turbine India Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gtindia2017-4540.
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Vapor compression refrigeration plant power consumption can be heavily reduced for a definite cooling power by the adoption of a power regeneration process internal to the simple cycle. Such a process takes benefit from the adoption of turbomachinery based vapor pressure amplifier. The selection of the wheel sizes, their machining to be adapted to the process and the addition of stator blades in the expander and a diffuser in the compressor path is discussed and tests results are presented. Improvements of the power consumption and of the COP of about 23–24% for a specified cooling power have been demonstrated.
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"Comparative Evaluation of Naturally ventilated Screenhouse and Evaporative Cooled Greenhouse based on Optimal Vapor Pressure Deficit." In 2016 ASABE International Meeting. American Society of Agricultural and Biological Engineers, 2016. http://dx.doi.org/10.13031/aim.20162454215.
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"Determining Tomato’s Growth Response to air Temperature, Relative Humidity and Vapor Pressure Deficit in Tropical Lowland Conditions." In 2014 ASABE Annual International Meeting. American Society of Agricultural and Biological Engineers, 2014. http://dx.doi.org/10.13031/aim.20141894987.
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Brown, Reid, and Daniel Cadol. "Vegetation density and vapor pressure deficit: Potential controls on dust flux at the Jackpile Uranium Mine, Laguna Pueblo, New Mexico." In 71st Annual Fall Field Conference. New Mexico Geological Society, 2021. http://dx.doi.org/10.56577/ffc-71.203.
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Yamada, Akira, Motoshige Yagyu, Chikako Iwaki, Tsukasa Sugita, Yoshiko Haruguchi, and Masashi Tanabe. "Development of Hydrogen Treatment System in Severe Accident: Part 4 — Study of Fission Products and Steam Effect on Hydrogen Treatment Characteristics." In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81759.
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A large amount of hydrogen is generated by the metal water-reaction in the Primary containment vessel (PCV) of light water reactors in the severe accident (SA). In the present accident management for boiling water reactor (BWR), vent of mixing gas with filtered vent is regarded as the most likely method that prevents the PCV overpressure. However, it is difficult to vent in early stage of SA because of high radioactive dose. Then we have been developing the hydrogen treatment system to prevent excessive pressure without PCV vent. In focusing on the oxidation-reduction reaction of metal oxides (MOs) with high reaction rate, we have been studying hydrogen treatment system using MOs as effective device under oxygen deficit conditions like PCV of BWR. In the previous studies, we evaluated the hydrogen treatment rate using a couple of MOs, and confirmed that CuO, Co3O4, and MnO2 were effective for the hydrogen oxidation under the oxygen-free condition. We also found that granules of these three MOs could achieve the goal of hydrogen treatment rate with reactor of hydrogen treatment system. We predicted that the performance of MOs decreased with exposure to steam and fission products (FPs) in the PCV during the hydrogen treatment, and investigated their influence. The objective of the present research is to investigate how the steam and FPs, which is supposed to be a reaction-inhibiting-factor, influence hydrogen treatment rate. Then, we conducted hydrogen treatment experiments using a fixed bed reactor with MOs layer. As the results, we confirmed that the hydrogen treatment rate of MnO2 decrease from 70 g/s/m3 to 15 g/s/m3 when partial pressure of vapor went above 0.1 MPa-abs, though, that of CuO didn’t depend on the partial pressure of vapor and sustain the same rate about 40 g/s/m3. We also confirmed that the hydrogen treatment rate was decreased with the consumption of granulated MOs faster than our expectation estimated with unreacted-core model*. We also estimated that CsI selected as typical FPs could not affect the hydrogen treatment rate of CuO. From these results, we have evaluated the reaction rate equation including the steam influence in CuO, which could estimate the hydrogen treatment rate of reactor unit. *Gas reacts only on the surface of solid and generates shell of products around reactants core. The core shrinks with reaction.
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Heggs, Peter John, and Abdelmadjid Alane. "Vacuum Operation of a Thermosyphon Reboiler." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22373.
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The research facility at the University of Manchester in the Morton Laboratory is a full scale replica of an industrial sized natural circulation thermosyphon reboiler, which comprises 50 tubes of 3 m length and 25.4 mm OD. The facility is operated under vacuum. Water is used as the process fluid and condensing steam is the heating source. Experimental datasets were obtained for the reboiler and have been presented in the form of profile plots of feed rate, fluid recirculation, recirculation ratio and vapour quality. The data elucidate the effect of pressure [0.1 to 1.0 bar] and heat duties [78 to 930 kW] on the performance of the reboiler. Three distinct modes of operation have been observed. Mode one is defined as a flow-induced instability or geysering (low heat duty) and exists below a definite transitional point that is independent of process pressure. Mode two is a region of stable operation that occurs above the threshold of the flow-induced instability, while mode three, which is defined as the heat-induced instability (density-wave instability), is pressure dependent obtained at high duties and is characterised by violent oscillations. These instability thresholds represent the lower and upper limits of operation of the reboiler. The region of stable operation is enveloped between the two limits and is very dependent on process pressure as it progressively becomes smaller as the vacuum becomes lower. These studies led to unique experimental observations, which revealed the existence of intermittent reversed flow in the entire loop. The use of throttling in the heat-induced unstable region to return to stable operation tends to be over a narrow range, outside of which the sole way to regain stability is to lower the heat load or increase the process pressure. In the region of flow-induced instability, throttling the fluid at the inlet is useless and actually makes the situation worse. These instabilities are alleviated by increasing the heat load.
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Ahmad, Mohammad, Zuhair Khan, Mian Muneeb Ur Rehman, Asghar Ali, and Shaheer Aslam. "A Study of Aluminum Doped ZnO Thin Films Developed via a Hybrid Method Involving Sputter Deposition and Wet Chemical Synthesis." In International Symposium on Advanced Materials. Switzerland: Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/p-s02qs7.
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Transparent conducting oxides (TCO) are semiconducting materials that are electrically conductive as well as optically transparent thus making them suitable for application in photovoltaics, transparent heat transfer windows, electrochromic windows, flexible display, and transparent electronics. One of the methods to enhance the conductivity of metal oxides is doping, however, it can adversely affect the optical transparency of metal oxide. Aluminum (Al) doped zinc (Zn) oxide (AZO) is an important TCO material whose optoelectronic properties heavily rely on the Al doping level. There are various methods to develop AZO thin films. However, since Al and Zn are high vapor pressure materials, and their precise content control isn’t that easy, that’s why we dedicated this study to devise a facile method of Al doping into the ZnO structure. We report a twostep synthesis route to develop AZO thin films over glass substrates. Sub stoichiometric zinc oxide (ZnOx) thin films were sputter deposited over glass employing RF magnetron sputtering at 70W and 9 x 10-3 Torr Ar pressure. To mitigate Zn losses during annealing at 450 °C, the films were first oxidized up to 200 °C in air so as to convert ZnOx into stoichiometric ZnO. To incorporate Al into the ZnO structure, Al was spin coated on top of ZnO from its stabilized sol of 0.07 molar aluminum nitrate nonahydrate in ethanol. The samples were subsequently annealed at 450 °C for 2h in air with a controlled heating ramp of 3 °C/min. The film morphology, microstructure, electronic, and optical characteristics were explored employing scanning electron microscopy, energy dispersive x-ray spectroscopy, Hall effect measurements, and UV-Vis-NIR spectrophotometry, respectively. We found that both the Al and oxygen (O) content affect the optoelectronic behavior of AZO. Even without Al doping, O deficient samples were found to be sufficiently conductive, however, the ZnOx is less transparent relative to O rich stoichiometric ZnO. Furthermore, if ZnOx is annealed at higher temperatures, it causes Zn losses, since Zn is a relatively high vapor pressure material. It degrades the film morphology as well. Once we have ZnO we can confidently treat it at 450 °C to allow Al diffusion into the interiors of the ZnO film. We found that AZO produced via this method is sufficiently conductive as well as transparent.
Reports on the topic "Vapour pressure deficit"
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McDowell, Nate. Understanding the impacts of elevated CO2 and vapor pressure deficit on tree mortality - CRADA 599 (Abstract). Office of Scientific and Technical Information (OSTI), June 2023. http://dx.doi.org/10.2172/2349352.
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Linker, Raphael, Murat Kacira, Avraham Arbel, Gene Giacomelli, and Chieri Kubota. Enhanced Climate Control of Semi-arid and Arid Greenhouses Equipped with Fogging Systems. United States Department of Agriculture, March 2012. http://dx.doi.org/10.32747/2012.7593383.bard.
Full textAbstract:
The main objectives were (1) to develop, implement and validate control procedures that would make it possible to maintain year-round air temperature and humidity at levels suitable for crop cultivation in greenhouses operating in arid and semi-arid regions and (2) to investigate the influence of the operational flexibility of the fogging system on the performance of the system. With respect to the development of climate controllers, we developed a new control approach according to which ventilation is used to maintain the enthalpy of the greenhouse air and fogging is used to adjust the humidity ratio inside the greenhouse. This approach is suitable mostly for greenhouses equipped with mechanized ventilation, and in which the air exchange rate can be controlled with enough confidence. The development and initial validation of the controllers were performed in a small experimental greenhouses located at the Agricultural Research Organization and very good tracking were obtained for both air temperature and relative humidity (maximum mean deviations over a 10-min period with constant setpoints lower than 2.5oC and 5% relative humidity). The robust design approach used to develop the controllers made it possible to transfer successfully these controllers to a much larger semi-commercial greenhouse located in the much drier Arava region. After only minimal adjustments, which did not require lengthy dedicated experiments, satisfactory tracking of the temperature and humidity was achieved, with standard deviation of the tracking error lower than 1oC and 5% for temperature and relative humidity, respectively. These results should help promote the acceptance of modern techniques for designing greenhouse climate controllers, especially since given the large variety of greenhouse structures (shape, size, crop system), developing high performance site-specific controllers for each greenhouse is not feasible. In parallel to this work, a new cooling control strategy, which considers the contribution of humidification and cooling from the crop, was developed for greenhouses equipped with natural ventilation. Prior to the development of the cooling strategy itself, three evapotranspiration models were compared in terms of accuracy and reliability. The cooling strategy that has been developed controls the amount of fog introduced into the greenhouse as well as the percentage of vent openings based on the desired vapor pressure deficit (VPD) and enthalpy, respectively. Numerical simulations were used to compare the performance of the new strategy with a constant fogging rate strategy based on VPD, and on average, the new strategy saved 36% water and consumed 30% less electric energy. In addition, smaller air temperature and relative humidity fluctuations were achieved when using the new strategy. Finally, it was demonstrated that dynamically varying the fog rate and properly selecting the number of nozzles, yields additional water and electricity savings.