Stomatal action directly feeds back on leaf turgor: New insights into the regulation of the plant water status from non-invasive pressure probe measurements

Universität Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, 97082 Würzburg, Germany.
The Plant Journal (Impact Factor: 5.97). 03/2010; 62(6):1072-82. DOI: 10.1111/j.1365-313X.2010.04213.x
Source: PubMed


Uptake of CO(2) by the leaf is associated with loss of water. Control of stomatal aperture by volume changes of guard cell pairs optimizes the efficiency of water use. Under water stress, the protein kinase OPEN STOMATA 1 (OST1) activates the guard-cell anion release channel SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1), and thereby triggers stomatal closure. Plants with mutated OST1 and SLAC1 are defective in guard-cell turgor regulation. To study the effect of stomatal movement on leaf turgor using intact leaves of Arabidopsis, we used a new pressure probe to monitor transpiration and turgor pressure simultaneously and non-invasively. This probe permits routine easy access to parameters related to water status and stomatal conductance under physiological conditions using the model plant Arabidopsis thaliana. Long-term leaf turgor pressure recordings over several weeks showed a drop in turgor during the day and recovery at night. Thus pressure changes directly correlated with the degree of plant transpiration. Leaf turgor of wild-type plants responded to CO(2), light, humidity, ozone and abscisic acid (ABA) in a guard cell-specific manner. Pressure probe measurements of mutants lacking OST1 and SLAC1 function indicated impairment in stomatal responses to light and humidity. In contrast to wild-type plants, leaves from well-watered ost1 plants exposed to a dry atmosphere wilted after light-induced stomatal opening. Experiments with open stomata mutants indicated that the hydraulic conductance of leaf stomata is higher than that of the root-shoot continuum. Thus leaf turgor appears to rely to a large extent on the anion channel activity of autonomously regulated stomatal guard cells.

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    • "For the monitoring of water stress, recent efforts have focused mainly on plant-based sensors with data transmission systems that allow automatic and continuous recording of main physiological variables related to the tree water status. This is the case for sap flow (Fernández et al., 2008; Ramos and Santos, 2009; Rousseaux et al., 2009), trunk diameter (Pérez-López et al., 2008; Moriana et al., 2010; Cuevas et al., 2010) and leaf turgor (Zimmermann et al., 2008; Ache et al., 2010; Fernández et al., 2011). Details on the required characteristics of any plant-based sensor to schedule irrigation are given in Fernández and Cuevas (2010). "
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    • "s was not significantly modified in pip2 ; 1 plants ( Supplemental Figure 11 ) . This lack of transpiration phenotype should be interpreted with care as it may reflect the cumulative effects of PIP2 ; 1 in guard cells and other cell types / organs . In particular , leaf vein cells are crucial for transferring water from the xylem into the lamina ( Ache et al . , 2010 ; Prado et al . , 2013 ) . Thus , a lack of function of PIP2 ; 1 at this site may result in a hydraulic limitation in veins , a drop in leaf water potential , and induction of stomatal closure . Conversely , a lack of function of PIP2 ; 1 in guard cells may antagonize stomatal closure . Because of these confounding physiological effects"
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    • "results provided in vivo evidences that OST1 kinase is involved in stomatal closure and activation of S-type anion channels induced by a biotic stimulus, YEL. Though it is well known that OST1 is essential for stomatal closure in response to a variety of stimuli (Melotto et al. 2006, Xie et al. 2006, Ache et al. 2010, Vahisalu et al. 2010, Xue et al. 2011, Merilo et al. 2013, Montillet et al. 2013), to our knowledge there is no evidence that kinase activity of OST1 is increased in guard cells in response to stimuli other than ABA. On the other hand, it has been reported that flg22 does not elicit activation Fig. 6 YEL-induced transient [Ca 2+ ] cyt elevations in Col-0 and ost1-3 guard cells expressing the Ca 2+ -sensing fluorescent protein YC 3.6. "
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