Soil drying and its effect on leaf conductance and CO2 assimilation of Vigna unguiculata (L.) Walp

Modelling the diurnal course of photosynthesis in oak leaves (Quercus robur L.) requires appropriate description of the dynamics of leaf photosynthesis of which diurnal variations in leaf conductance and in CO2 assimilation are essential components. We propose and analyse a simple photosynthesis model with three variables: leaf conductance (gs), the CO2 partial pressure inside the leaf (pi), and a pool of Calvin cycle intermediates (aps). The environmental factors light (I) and vapour pressure deficit (VPD) are used to formulate a target function G(I, VPD) from which the actual leaf conductance is calculated. Using this gs value and a CO2 consumption term representing CO2 fixation, a differential equation for pi is derived. Carboxylation corresponds to the sink term of the pi pool and is assumed to be feedback-inhibited by aps. This simple model is shown to produce reasonable to excellent fits to data on the diurnal time courses of photosythesis, pi and gs sampled for oak leaves.

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Leaf Conductance in Relation to Rate of CO2 Assimilation

PLANT PHYSIOLOGY ◽

10.1104/pp.78.4.830 ◽

1985 ◽

Vol 78 (4) ◽

pp. 830-834 ◽

Cited By ~ 100

Author(s):

Suan-Chin Wong ◽

Ian R. Cowan ◽

Graham D. Farquhar

Keyword(s):

Co2 Assimilation ◽

Leaf Conductance

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Carbon Dioxide Assimilation by Pineapple Plants, Ananas comosus (L.) Merr. II. Effects of Variation of the Day/Night Temperature Regime

Functional Plant Biology ◽

10.1071/pp9800375 ◽

1980 ◽

Vol 7 (4) ◽

pp. 375 ◽

Cited By ~ 7

Author(s):

TF Neales ◽

PJM Sale ◽

CP Meyer

Keyword(s):

Temperature Regime ◽

Co2 Assimilation ◽

Leaf Conductance ◽

Ananas Comosus ◽

Co2 Efflux ◽

Night Temperature ◽

Cam Plants ◽

Ambient Temperatures ◽

Single Leaf ◽

Enclosure Methods

The effects of variation of day/night temperature regime on the diurnal patterns of CO2 assimilation of pineapple plants were examined using single leaf and field enclosure methods. At day temperatures of 30°C, increasing night temperatures from 20 to 35°C reduced the total assimilation of CO2 per daily light/dark cycle from 6.5 to 1.3 g CO2 m-2 (leaf area) day-1, and also reduced the proportion of total CO2 assimilation that occurred at night from c. 90% to c. 40%. Decreasing day temperatures (30 to 10°C) had little effect on total daily CO2 assimilation in warm (25°C) nights, but reduced it in cooler (15°C) nights. At day temperatures of <152C, CO2 assimilation took place predominantly (60-100%) in the photoperiod. In cool (10°C) days, the normal inverted stomatal rhythm of CAM plants was reversed; leaf conductance was high (c. 1.0 mm s-1) throughout the photoperiod and a large CO2 efflux was observed, lasting c. 2 h, at the beginning of the dark period. Leaf conductance of pineapples, by day and by night, is strongly influenced by ambient temperatures, with cool conditions favouring stomatal opening.

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Abscisic acid in apoplastic sap can account for the restriction in leaf conductance of white lupins during moderate soil drying and after rewatering

Plant Cell & Environment ◽

10.1111/j.1365-3040.1994.tb00179.x ◽

1994 ◽

Vol 17 (7) ◽

pp. 845-852 ◽

Cited By ~ 29

Author(s):

M. J. CORREIA ◽

J. S. PEREIRA

Keyword(s):

Abscisic Acid ◽

Leaf Conductance ◽

Soil Drying

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Leaf Conductance in Relation to Rate of CO2 Assimilation

PLANT PHYSIOLOGY ◽

10.1104/pp.78.4.821 ◽

1985 ◽

Vol 78 (4) ◽

pp. 821-825 ◽

Cited By ~ 192

Author(s):

Suan-Chin Wong ◽

Ian R. Cowan ◽

Graham D. Farquhar

Keyword(s):

Co2 Assimilation ◽

Leaf Conductance

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An Empirical Model of Net Photosynthesis and Leaf Conductance for the Simulation of Diurnal Courses of CO2 and H2O Exchange

Functional Plant Biology ◽

10.1071/pp9850513 ◽

1985 ◽

Vol 12 (5) ◽

pp. 513 ◽

Cited By ~ 24

Author(s):

M Kuppers ◽

ED Schulze

Keyword(s):

Gas Exchange ◽

Empirical Model ◽

Climatic Factors ◽

Net Photosynthesis ◽

Co2 Assimilation ◽

Leaf Conductance ◽

Co2 Uptake ◽

Diurnal Courses ◽

Humidity Response ◽

Steady State Responses

An empirical model of CO2 uptake and water loss of leaves is established using steady-state responses of gas exchange to climatic factors as input. From the model the response surface of net CO2 assimilation and leaf conductance to climate can be derived. The model consists of two submodels, one describing the response of CO2 uptake to light and temperature, the other describing the response of leaf conductance to temperature and humidity. Both submodels are joined via the linear relationship between CO2 uptake and leaf conductance at short-term (minutes) variation of irradiance. From the humidity response of leaf conductance and the 'demand function' (Raschke 1979) of CO2 uptake in the mesophyll, the effect of stomata on the diffusion of CO2 between leaf and air is determined. The model is tested by comparing measured and calculated diurnal courses of gas exchange for two plants of Pinus silvestris, differing in photosynthetic capacity due to different levels of magnesium nutrition. Applications and limitations of the model are discussed.

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Hydraulic conductance of intact plants of two contrasting sorghum lines, SC15 and SC1205

Functional Plant Biology ◽

10.1071/fp12338 ◽

2013 ◽

Vol 40 (7) ◽

pp. 730 ◽

Cited By ~ 15

Author(s):

Sunita Choudhary ◽

Thomas R. Sinclair ◽

P. V. Vara Prasad

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Use ◽

Hydraulic Conductance ◽

Leaf Conductance ◽

Soil Drying ◽

Water Deficits ◽

Intact Plants ◽

The Impact

Low plant hydraulic conductance has been hypothesised as an approach to decrease the rate of soil water use, resulting in soil water conservation for use during late season water deficits. The impact of leaf hydraulic conductance (Kleaf) on water use characteristics was explored by comparing two sorghum (Sorghum bicolor (L.) Moench) genotypes that had been found to differ in Kleaf. Genotype SC15 had a much lower leaf conductance than genotype SC1205. Four sets of experiments were undertaken to extend the comparison to the impact of differences in Kleaf on the plant water budget. (1) Measurements of hydraulic conductance of intact plants confirmed that leaf conductance of SC15 was lower than that of SC1205. (2) The low leaf conductance of SC15 was associated with a decrease in transpiration during soil drying at a higher soil water content than that of SC1205. (3) SC15 had a restricted transpiration rate at vapour pressure deficits (VPD) above 2.1 kPa, whereas SC1205 did not. (4) Treatment with aquaporin inhibitors showed substantial differences in the sensitivity of the transpiration response between the genotypes. These results demonstrated that low Kleaf in SC15 was associated with conservative water use by restricting transpiration at higher soil water content during soil drying and under high VPD. Tests with inhibitors indicate that these differences may be linked to differences between their aquaporin populations. The differences between the two genotypes indicated that the traits exhibited by SC15 would be desirable in environments where soil water deficits develop.

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