Stomatal closure in groups

Topography of Photosynthetic Activity of Leaves Obtained from Video Images of Chlorophyll Fluorescence

by Daley P. F., Raschke K., Ball J. T., Berry J. A. (1989)

In Plant Physiol. 90: 1233-1238 –

https://www.academia.edu/37479199/Topography_of_Photosynthetic_Activity_of_Leaves_Obtained_from_Video_Images_of_Chlorophyll_Fluorescence

Abstract

Regulation of stomatal conductance

Fig. 1. A scheme showing the mass and energy fluxes along with the interactions between these considered in the complete model. Fluxes are shown as solid lines. Regulatory interactions are shown as dashed lines, c, e and T stand for CO2, H20 vapor concentrations and temperature, respectively. The subscripts a, s and 1, refer to properties in ambient air, at the leaf surface and of the leaf, respectively. Rsky specifies the long-wave length radiation input from the sky and Rso~ar represents solar radiation.

 

Physiological and environmental regulation of stomatal conductance, photosynthesis and transpiration: a model that includes a laminar boundary layer

by Collatz G. J., Grivet C., Ball J. T., Berry J. A. (1991)

G. James Collatz, ^a J. Timothy Ball, ^b  Cyril Grivet, ^a  Joseph A. Berry, ^a

^a

Carnegie Institution of Washington, Department of Plant Biology, 290 Panama Street, Stanford, CA 94305, USA

^b

Desert Research Institute, PO Box 60220, Reno, NV 89622, USA

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in Agricultural and Forest Meteorology 54 – 107-136 – https://doi.org/10.1016/0168-1923(91)90002-8 –

https://www.sciencedirect.com/science/article/pii/0168192391900028

Abstract

This paper presents a system of models for the simulation of gas and energy exchange of a leaf of a C₃ plant in free air. The physiological processes are simulated by sub-models that: (a) give net photosynthesis (A_n) as a function of environmental and leaf parameters and stomatal conductance (g_s); (b) give g, as a function of the concentration of CO₂ and H₂O in air at the leaf surface and the current rate of photosynthesis of the leaf. An energy balance and mass transport sub-model is used to couple the physiological processes through a variable boundary layer to the ambient environment.

The models are based on theoretical and empirical analysis of g_s, and A_n measured at the leaf level, and tests with intact attached leaves of soybeans show very good agreement between predicted and measured responses of g_s and A_n over a wide range of leaf temperatures (20–35°C), CO₂ concentrations (10–90 Pa), air to leaf water vapor deficits (0.5–3.7 kPa) and light intensities (100–2000 μmol m⁻²s⁻¹).

The combined models were used to simulate the responses of latent heat flux (λE) and g_s for a soybean canopy for the course of an idealized summer day, using the ‘big-leaf’ approximation. Appropriate data are not yet available to provide a rigorous test of these simulations, but the response patterns are similar to field observations. These simulations show a pronounced midday depression of λE and g_sat low or high values of boundary-layer conductance.

Deterioration of plant water relations during midday has often been invoked to explain this common natural phenomenon, but the present models do not consider this possibility. Analysis of the model indicates that the simulated midday depression is, in part, the result of positive feedback mediated by the boundary layer. For example, a change in g_s affects A_n and λE. As a consequence, the temperature, humidity and CO₂concentration of the air in the proximity of the stomata (e.g. the air at the leaf surface) change and these, in turn, affect g_s.

The simulations illustrate the possible significance of the boundary layer in mediating feedback loops which affect the regulation of stomatal conductance and λE. The simulations also examine the significance of changing the response properties of the photosynthetic component of the model by changing leaf protein content or the CO₂ concentration of the atmosphere.