scholarly journals Optimal carbon partitioning reconciles the apparent divergence between optimal and observed canopy profiles of photosynthetic capacity

2020 ◽  
Author(s):  
Thomas N. Buckley
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Photosynthetic Capacity ◽  
Optimization Theory ◽  
Carbon Partitioning ◽  
Leaf Water ◽  
Nitrogen Partitioning ◽  
Gas Exchange Parameters ◽  
Evaporative Demand ◽  
Marginal Returns

SummaryResearch conductedPhotosynthetic capacity per unit irradiance is greater, and the marginal carbon revenue of water (∂A/∂E) is smaller, in shaded leaves than sunlit leaves, apparently contradicting optimization theory. I tested the hypothesis that these patterns arise from optimal carbon partitioning subject to biophysical constraints on leaf water potential.MethodsIn a whole plant model with two canopy modules, I adjusted carbon partitioning, nitrogen partitioning and leaf water potential to maximize carbon profit or canopy photosynthesis, and recorded how gas exchange parameters compared between shaded and sunlit modules in the optimum.Key resultsThe model predicted that photosynthetic capacity per unit irradiance should be larger, and ∂A/∂E smaller, in shaded modules compared to sunlit modules. This was attributable partly to radiation-driven differences in evaporative demand, and partly to differences in hydraulic conductance arising from the need to balance marginal returns on stem carbon investment between modules. The model verified, however, that invariance in the marginal carbon revenue of N (∂A/∂N) is in fact optimal.ConclusionThe Cowan-Farquhar optimality solution (invariance of ∂A/∂E) does not apply to spatial variation within a canopy. The resulting variation in carbon-water economy explains differences in capacity per unit irradiance, reconciling optimization theory with observations.

scholarly journals The Effect of Grapevine Age (Vitis vinifera L. cv. Zinfandel) on Phenology and Gas Exchange Parameters over Consecutive Growing Seasons

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 311
Author(s):  
Vegas Riffle ◽  
Nathaniel Palmer ◽  
L. Federico Casassa ◽  
Jean Catherine Dodson Peterson
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Management Practices ◽  
Leaf Water ◽  
Sugar Accumulation ◽  
Gas Exchange Parameters ◽  
Growing Season Length ◽  
Growing Seasons ◽  
Exchange Parameters

Unlike most crop industries, there is a strongly held belief within the wine industry that increased vine age correlates with quality. Considering this perception could be explained by vine physiological differences, the purpose of this study was to evaluate the effect of vine age on phenology and gas exchange parameters. An interplanted, dry farmed, Zinfandel vineyard block under consistent management practices in the Central Coast of California was evaluated over two consecutive growing seasons. Treatments included Young vines (5 to 12 years old), Control (representative proportion of young to old vines in the block), and Old vines (40 to 60 years old). Phenology, leaf water potential, and gas exchange parameters were tracked. Results indicated a difference in phenological progression after berry set between Young and Old vines. Young vines progressed more slowly during berry formation and more rapidly during berry ripening, resulting in Young vines being harvested before Old vines due to variation in the timing of sugar accumulation. No differences in leaf water potential were found. Young vines had higher mid-day stomatal conductance and tended to have higher mid-day photosynthetic rates. The results of this study suggest vine age is a factor in phenological timing and growing season length.

scholarly journals Rapid changes in root HvPIP2;2 aquaporins abundance and ABA concentration are required to enhance root hydraulic conductivity and maintain leaf water potential in response to increased evaporative demand

2018 ◽  
Vol 45 (2) ◽  
pp. 143 ◽  
Author(s):  
Dmitry S. Veselov ◽  
Guzel V. Sharipova ◽  
Stanislav Yu. Veselov ◽  
Ian C. Dodd ◽  
Igor Ivanov ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Water Potential ◽  
Air Temperature ◽  
Leaf Water Potential ◽  
Vapour Pressure Deficit ◽  
Leaf Water ◽  
Evaporative Demand ◽  
Root Hydraulic Conductivity ◽  
Rapid Changes ◽  
Aba Content

To address the involvement of abscisic acid (ABA) in regulating transpiration and root hydraulic conductivity (LpRoot) and their relative importance for maintaining leaf hydration, the ABA-deficient barley mutant Az34 and its parental wild-type (WT) genotype (cv. Steptoe) were grown in hydroponics and exposed to changes in atmospheric vapour pressure deficit (VPD) imposed by air warming. WT plants were capable of maintaining leaf water potential (ψL) that was likely due to increased LpRoot enabling higher water flow from the roots, which increased in response to air warming. The increased LpRoot and immunostaining for HvPIP2;2 aquaporins (AQPs) correlated with increased root ABA content of WT plants when exposed to increased air temperature. The failure of Az34 to maintain ψL during air warming may be due to lower LpRoot than WT plants, and an inability to respond to changes in air temperature. The correlation between root ABA content and LpRoot was further supported by increased root hydraulic conductivity in both genotypes when treated with exogenous ABA (10−5 M). Thus the ability of the root system to rapidly regulate ABA levels (and thence aquaporin abundance and hydraulic conductivity) seems important to maintain leaf hydration.

scholarly journals Physiological effects of water deficit on two oil palm (Elaeis guineensis Jacq.) genotypes

2015 ◽  
Vol 33 (2) ◽  
pp. 164-173 ◽  
Author(s):  
Seyed Mehdi Jazayeri ◽  
Yurany Dayanna Rivera ◽  
Jhonatan Eduardo Camperos-Reyes ◽  
Hernán Mauricio Romero
Keyword(s):  
Stomatal Conductance ◽  
Gas Exchange ◽  
Water Potential ◽  
Water Deficit ◽  
Leaf Water Potential ◽  
Oil Palm ◽  
Photosynthetic Capacity ◽  
Elaeis Guineensis ◽  
Leaf Water ◽  
Physiological Effects

Water supply is the main limiting factor that affects oil palm (Elaeis guineensis Jacq.) yield. This study aimed to evaluate the gas exchange and photosynthetic capacity, determine the physiological effects and assess the tolerance potential of oil palm genotypes under water-deficit conditions. The two oil palm commercial genotypes IRHO1001 and IRHO7010 were exposed to soil water potentials of -0.042 MPa (field capacity or well-watered) or -1.5 MPa (drought-stressed). The leaf water potential and gas exchange parameters, including photosynthesis, stomatal conductance, transpiration and water use efficiency (WUE), as well as the photosynthesis reduction rate were monitored at 4 and 8 weeks after treatment. The IRHO7010 genotype showed fewer photosynthesis changes and a smaller photosynthetic reduction under the prolonged water deficit conditions of 23% at 4 weeks after the treatment as compared to 53% at 8 weeks after treatment, but the IRHO1001 genotype showed 46% and 74% reduction at the two sampling times. 'IRHO7010' had a higher stomatal conductance and transpiration potential than 'IRHO1001' during the water shortage. The WUE and leaf water potential were not different between the genotypes during dehydration. The data suggested that 'IRHO7010' had a higher photosynthetic capacity during the drought stress and was more drought-tolerant than 'IRHO1001'.

Rubber Trees Affected by Necrotic Tapping Panel Dryness Exhibit Poor Transpiration Regulation under Atmospheric Drought

2013 ◽  
Vol 844 ◽  
pp. 3-6
Author(s):  
Supat Isarangkool Na Ayutthaya ◽  
Frederic C. Do
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Water Status ◽  
Leaf Water ◽  
Evaporative Demand ◽  
Predawn Leaf Water Potential ◽  
Long Period ◽  
Tree Transpiration ◽  
Tapping Panel Dryness ◽  
Whole Tree

The objective was to study the responses in water status and transpiration regulation of rubber trees affected by the necrotic Tapping Panel Dryness (N) by comparison with healthy trees (H). The experiment was done with 5 N trees and 5 H trees of clone RRIM600 during well soil watered periods differing in evaporative demand intensity, May and August 2007. The study compared predawn leaf water potential (ψpd), midday leaf water potential (ψmid), whole tree hydraulic conductance (K), midday sapflow density (Js) and tree transpiration (ET) with the average girth size 51.54 cm of H tree and 52.66 cm of N tree. These variables, investigated in the high evaporative demand day (ETO = 3.71 mm day-1) on 23 May 2007 and low evaporative demand day (ETO = 1.75 mm day-1) on 22 Aug 2007, did not significantly differ between tree types. However, over a long period, in high evaporative demand, ET tended to be higher in N trees. Expression of ET versus ETO confirmed different relationships between the two tree types with a higher plateau of maximum transpiration for N trees. Our results suggested that individuals with relatively poor transpiration regulation could be more sensitive to necrotic Tapping Panel Dryness syndrome.

scholarly journals Variation of leaf water potential and leaf gas exchange parameters of seven Silver linden (Tilia tomentosa Moench) genotypes in urban environment

Topola ◽  
2020 ◽  
pp. 15-24
Author(s):  
Lazar Kesić ◽  
Vanja Vuksanović ◽  
Velisav Karaklić ◽  
Erna Vaštag
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Urban Environment ◽  
Leaf Water Potential ◽  
Leaf Gas Exchange ◽  
Intercellular Co2 Concentration ◽  
Leaf Water ◽  
Gas Exchange Parameters ◽  
Tilia Tomentosa ◽  
Exchange Parameters

Differences between genotypes are considered to be the most important requisite for a resilient urban forest. Analyses of physiological traits, such as leaf water potential and leaf gas exchange could provide useful insight into the capacity of different species and genotypes to grow in harsh urban environments. In the present study, a variation of midday (Psmd) and predawn (Pspd) leaf water potential, net photosynthesis (A), rate of transpiration (E), stomatal conductance (gs), and intercellular CO2 concentration (Ci) of seven Silver linden genotypes (Tilia tomentosa Moench), planted in the urban environment in Novi Sad, were examined. Analysis of variance and LSD tests were used to show differences between studied silver linden genotypes. The results showed significant differences for all observed leaf gas exchange parameters (A, E, gs, Ci, Pspd and Psmd) between genotypes. The results indicate better physiological performances of genotypes T3, in comparison to other observed genotypes under the prevailing environmental condition of the studied site in the urban environment.

scholarly journals Azospirillum baldaniorum Sp245 Induces Physiological Responses to Alleviate the Adverse Effects of Drought Stress in Purple Basil

Plants ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1141
Author(s):  
Lorenzo Mariotti ◽  
Andrea Scartazza ◽  
Maurizio Curadi ◽  
Piero Picciarelli ◽  
Annita Toffanin
Keyword(s):  
Gas Exchange ◽  
Plant Growth ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Water Status ◽  
Xylem Sap ◽  
Leaf Water ◽  
Growth And Yield ◽  
Gas Exchange Parameters ◽  
Leaf Water Status

Azospirillum spp. are plant growth-promoting rhizobacteria (PGPR) that exert beneficial effects on plant growth and yield of agronomically important plant species. The aim of this study was to investigate the effects of a root treatment with Azospirillum baldaniorum Sp245 on hormones in xylem sap and physiological performance in purple basil (Ocimum basilicum L. cv. Red Rubin) plants grown under well-watered conditions and after removing water. Treatments with A. baldaniorum Sp245 included inoculation with viable cells (1ˑ107 CFU mL–1) and addition of two doses of filtered culture supernatants (non-diluted 1ˑ108 CFU mL–1, and diluted 1:1). Photosynthetic activity, endogenous level of hormones in xylem sap (salicylic acid, jasmonic acid, and abscisic acid), leaf pigments, leaf water potential, water-use efficiency (WUE), and drought tolerance were determined. Fluorescence and gas exchange parameters, as well as leaf water potential, showed that the highest dose of filtered culture supernatant improved both photosynthetic performance and leaf water status during water removal, associated with an increase in total pigments. Moreover, gas exchange analysis and carbon isotope discrimination found this bacterial treatment to be the most effective in inducing an increase of intrinsic and instantaneous WUE during water stress. We hypothesize that the benefits of bacterial treatments based on A. baldaniorum Sp245 are strongly correlated with the synthesis of phytohormones and the induction of plant-stress tolerance in purple basil.

Use of a Hydraulic Press for Estimation of Leaf Water Potential in Grain Sorghum 1

1986 ◽  
Vol 78 (4) ◽  
pp. 749-751 ◽  
Author(s):  
S. K. Hicks ◽  
R. J. Lascano ◽  
C. W. Wendt ◽  
A. B. Onken
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Grain Sorghum ◽  
Hydraulic Press ◽  
Leaf Water
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