Stomatal patchiness and leaf carboxylation capacity

 

 

Photosynthesis inhibition during gas exchange oscillations in ABA-treated Helianthus annuus: relative role of stomatal patchiness and leaf carboxylation capacity

by Šantrůček J., Hronkova M., Kveton J. K., Sage R. F. (2003)

J. ŠANTRŮČEK*,**,+, M. HRONKOVÁ*,**, J. KVĚTOŇ*,**, and R.F. SAGE***

* Department of Photosynthesis, Institute of Plant Molecular Biology, Academy of Sciences of the Czech Republic, Branišovská 31, CZ-370 05 České Budějovice, Czech Republic

** The University of South Bohemia, Faculty of Biology and Institute of Physical Biology, Photosynthesis Research Centre, CZ-370 05 České Budějovice, Czech Republic

*** Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada

===

in PHOTOSYNTHETICA 41 (2): 241-252 –

http://www.esalq.usp.br/lepse/imgs/conteudo_thumb/Photosynthesis-inhibition-during-gas-exchange-oscillations-in-ABA-treated-Helianthus-annuus–relative-role-of-stomatal-patchiness-and-leaf-carboxylation-capacity.pdf

Abstract

Environmental factors that induce spatial heterogeneity of stomatal conductance, gs, called stomatal patchiness, also reduce the photochemical capacity of CO2 fixation, yet current methods cannot distinguish between the relative effect of stomatal patchiness and biochemical limitations on photosynthetic capacity. We evaluate effects of stomatal patchiness and the biochemical capacity of CO2 fixation on the sensitivity of net photosynthetic rate (PN) to stomatal conductance (gs), θ (θ = δPN/δgs).

A qualitative model shows that stomatal patchiness increases the sensitivity θ while reduced biochemical capacity of CO2 fixation lowers θ. We used this feature to distinguish between stomatal patchiness and mesophyll impairments in the photochemistry of CO2 fixation.

We compared gas exchange of sunflower (Helianthus annuus L.) plants grown in a growth chamber and fed abscisic acid, ABA (10–5 M), for 10 d with control plants (–ABA). PN and gs oscillated more frequently in ABA-treated than in control plants when the leaves were placed into the leaf chamber and exposed to a dry atmosphere.

When compared with the initial CO2 response measured at the beginning of the treatment (day zero), both ABA and control leaves showed reduced PN at particular sub-stomatal CO2 concentration (ci) during the oscillations. A lower reduction of PN at particular gs indicated overestimation of ci due to stomatal patchiness and/or omitted cuticular conductance, gc.

The initial period of damp oscillation was characterised by inhibition of chloroplast processes while stomatal patchiness prevailed at the steady state of gas exchange. The sensitivity θ remained at the original pre-treatment values at high gs in both ABA and control plants. At low gs, θ decreased in ABA-treated plants indicating an ABA-induced impairment of chloroplast processes.

In control plants, gc neglected in the calculation of gs was the likely reason for apparent depression of photosynthesis at low gs.

Acclimation of stomatal conductance to a CO2-enriched atmosphere and elevated temperature

 

Photo credit: Google

Comparison of nettle-leaf goosefoot (Chenopodium murale), with green leaves and flowers on the left, and fat hen (Chenopodium album), with greyish-green leaves

 

Acclimation of stomatal conductance to a CO₂-enriched atmosphere and elevated temperature in Chenopodium album.

by Šantrůček J., Sage R. F. (1996)

in Australian Journal of Plant Physiology 23, 467–478 – https://doi.org/10.1071/PP9960467 –

CrossRef |-

http://www.publish.csiro.au/fp/PP9960467

Abstract

Acclimation of stomatal conductance to different CO₂ and temperature regimes was determined in Chenopodium album L. plants grown at one of three treatment conditions: 23ºC and 350 μmol CO₂ mol^-1 air; 34ºC and 350 μmol mol^-1; and 34ºC and 750 μmol mol^-1.

Stomatal conductance (g_s) as a function of intercellular CO₂(C_i) was determined for each treatment at 25 and 35ºC, and these data were used to estimate gains of the feedback loops linking changes in intercellular CO₂ with stomatal conductance and net CO₂ assimilation.

Growth temperature affected the sensitivity of stomata to measurement temperature in a pattern that was influenced by intercellular CO₂. Stomatal conductance more than doubled at intercellular CO₂ varying between 200 and 600 μmol mol^-1 as leaf temperature increased from 25 to 35ºC for plants grown at 23ºC.

In contrast, stomatal conductance was almost unaffected by measurement temperature in plants grown at 34ºC. Elevated growth CO₂ attenuated the response of stomatal conductance to CO₂, but growth temperature did not.

Stomatal sensitivity to C_iwas extended to higher C_i in plants grown in elevated CO₂. As a result, plants grown at 750 μmol mol^-1 CO₂ had higher C_i/C_a at ambient CO₂ values between 300 and 1200 ¼mol mol-1 than plants grown at 350 ¼mol mol-1 CO2.

The gain of the stomatal loop was reduced in plants grown at elevated CO₂ or at lower temperature when compared to plants grown at 350 μmol mol^-1 and 34°C. Both photosynthetic and stomatal loop gains acclimated to elevated CO₂ in proportion so that their ratio, integrated over the range of C_i in which the plant operates, remained constant.

Water use efficiency (WUE) more than doubled after a short-term doubling of ambient CO₂. However, the WUE of plant grown and measured at elevated CO₂ was only about 1.5 times that of plant transiently exposed to elevated CO₂, due to stomatal acclimation. An optimal strategy of water use was maintained for all growth treatments.