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

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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.

STOMAGEN and stomatal development

 

Light-induced STOMAGEN-mediated stomatal development in Arabidopsis leaves

by Hronková M., Wiesnerová D., Šimková M., 

Skůpa P.,

 Dewitte W.,

 Vráblová M.,

 Zažímalová E.,

 Šantrůček J. (2015)

in J. Exp. Bot. (2015) 66 (15):4621-4630. – doi: 10.1093/jxb/erv233 – 

http://jxb.oxfordjournals.org/content/66/15/4621.abstract 

Abstract

The initiation of stomata, microscopic valves in the epidermis of higher plants that control of gas exchange, requires a co-ordinated sequence of asymmetric and symmetric divisions, which is under tight environmental and developmental control. Arabidopsis leaves grown under elevated photosynthetic photon flux density have a higher density of stomata.STOMAGEN encodes an epidermal patterning factor produced in the mesophyll, and our observations indicated that elevated photosynthetic irradiation stimulates STOMAGEN expression.

Our analysis of gain and loss of function of STOMAGEN further detailed its function as a positive regulator of stomatal formation on both sides of the leaf, not only in terms of stomatal density across the leaf surface but also in terms of their stomatal index.

STOMAGEN function was rate limiting for the light response of the stomatal lineage in the adaxial epidermis. Mutants in pathways that regulate stomatal spacing in the epidermis and have elevated stomatal density, such as stomatal density and distribution (sdd1) and too many mouth alleles, displayed elevated STOMAGEN expression, suggesting that STOMAGEN is either under the direct control of these pathways or is indirectly affected by stomatal patterning, suggestive of a feedback mechanism.

These observations support a model in which changes in levels of light irradiation are perceived in the mesophyll and control the production of stomata in the epidermis by mesophyll-produced STOMAGEN, and whereby, conversely, stomatal patterning, either directly or indirectly, influences STOMAGEN levels.

Production of stomata in the epidermis by mesophyll-produced STOMAGEN

 

Light-induced STOMAGEN-mediated stomatal development in Arabidopsis leaves

by Hronkova M., Wiesnerova D., Simkova M., Skupa P., Dewitte W., Vrablova M., Zazimalova E., Santrucek J. (2015)

in Journal of Experimental Botany : J. Exp. Bot. (2015) 66 (15):4621-4630.doi: 10.1093/jxb/erv233 

First published online: May 22, 2015

Abstract

The initiation of stomata, microscopic valves in the epidermis of higher plants that control of gas exchange, requires a co-ordinated sequence of asymmetric and symmetric divisions, which is under tight environmental and developmental control.

Arabidopsis leaves grown under elevated photosynthetic photon flux density have a higher density of stomata.

STOMAGEN encodes an epidermal patterning factor produced in the mesophyll, and our observations indicated that elevated photosynthetic irradiation stimulates STOMAGEN expression. Our analysis of gain and loss of function of STOMAGEN further detailed its function as a positive regulator of stomatal formation on both sides of the leaf, not only in terms of stomatal density across the leaf surface but also in terms of their stomatal index. STOMAGEN function was rate limiting for the light response of the stomatal lineage in the adaxial epidermis. Mutants in pathways that regulate stomatal spacing in the epidermis and have elevated stomatal density, such as stomatal density and distribution (sdd1) and too many mouth alleles, displayed elevated STOMAGEN expression, suggesting that STOMAGEN is either under the direct control of these pathways or is indirectly affected by stomatal patterning, suggestive of a feedback mechanism.

These observations support a model in which changes in levels of light irradiation are perceived in the mesophyll and control the production of stomata in the epidermis by mesophyll-produced STOMAGEN, and whereby, conversely, stomatal patterning, either directly or indirectly, influences STOMAGEN levels.

See the text: Journal of Experimental Botany