Article

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: 6.82). 03/2010; 62(6):1072-82. DOI: 10.1111/j.1365-313X.2010.04213.x
Source: PubMed

ABSTRACT 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.

1 Follower
 · 
128 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The global shortage of fresh water is one of our most severe agricultural problems, leading to dry and saline lands that reduce plant growth and crop yield. Here we review recent work highlighting the molecular mechanisms allowing some plant species and genotypes to maintain productivity under water stress conditions, and suggest molecular modifications to equip plants for greater production in water-limited environments. Aquaporins (AQPs) are thought to be the main transporters of water, small and uncharged solutes and CO2 through plant cell membranes, thus linking leaf CO2 uptake from the intercellular airspaces to the chloroplast with water loss pathways. AQPs appear to play a role in regulating dynamic changes of root, stem and leaf hydraulic conductivity, especially in response to environmental changes, opening the door to using AQP expression to regulate plant water use efficiency. We highlight the role of vascular AQPs in regulating leaf hydraulic conductivity and raise questions regarding their role (as well as tonoplast AQPs) in determining the plant isohydric threshold, growth rate, fruit yield production and harvest index. The tissue specific or cell specific expression of AQPs is discussed as a tool to increase yield relative to control plants under both normal and water-stressed conditions.
    Plant Cell and Environment 07/2014; DOI:10.1111/pce.12410 · 5.91 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Systemic signalling of photooxidative stress from a high light (HL)-exposed leaf to a shaded leaf results in systemic acquired acclimation (SAA) in the distal tissue. As yet unanswered questions in systemic photooxidative stress signalling are in regard to what type of signal and what form of travel the signal takes from a small area of exposed tissue to as yet unstressed distal tissues. Issues such as the specificity of different stress responses, how different ROS signalling pathways converge, and antagonistically regulated systems are all currently being investigated. The majority of studies in this field, however, focus on the intercellular signalling aspects rather than leaf-to-leaf movement of the signal. Traditional studies of biotic long-distance signalling have not as yet been comprehensively applied to abiotic stress signalling research, particularly in regard to whether an abiotic signal is able to rapidly travel through the vasculature from leaf to leaf. This review covers literature relating to the effects that HL intensity and the production of ROS have on the stress signalling processes of light perception, retrograde and intercellular signalling, as well as leaf-to-leaf systemic signalling in the model organism Arabidopsis thaliana.
    Long-Distance Systemic Signaling and Communication in Plants, Edited by František Baluška, 01/2013: chapter Systemic Photooxidative Stress Signalling: pages 251-274; Springer Berlin Heidelberg., ISBN: 978-3-642-36470-9
  • [Show abstract] [Hide abstract]
    ABSTRACT: Our understanding of the cellular role of aquaporins (AQPs) in the regulation of whole-plant hydraulics, in general, and extravascular, radial hydraulic conductance in leaves (Kleaf), in particular, is still fairly limited. We hypothesized that the aquaporins of the vascular bundle sheath (BS) cells regulate Kleaf. To examine this hypothesis, AQP genes were silenced using artificial microRNAs (amiRNAs) that were expressed constitutively or specifically targeted to the BS. MicroRNA sequences were designed to target all five AQP genes from thePIP1 subfamily. Our results show that the constitutively silenced PIP1 (35S promoter) plants had decreased PIP1 transcript and protein levels and decreased mesophyll and BS osmotic water permeability (Pf), mesophyll conductance of CO2 (gm), photosynthesis (AN), Kleaf, transpiration and shoot biomass. Plants in which the PIP1 subfamily was silenced only in the BS (SCR:mir plants) exhibited decreased mesophyll and BS Pf and decreased Kleaf, but no decreases in the rest of the parameters listed above, with the net result of increased shoot biomass. We excluded the possibility of SCR promoter activity in the mesophyll. Hence, the fact that SCR:mir mesophyll exhibited reduced Pf, but not reduced gm suggests that the BS-mesophyll hydraulic continuum acts as a feed-forward control signal. The role of AQPs in the hierarchy of the hydraulic signal pathway controlling leaf water status under normal and limited-water conditions is discussed. Keywords: Plasma membrane intrinsic proteins (PIPs), Aquaporins (AQPs), Bundle sheath, Leaf hydraulic conductivity (Kleaf), Artificial microRNA (amiRNA).
    Plant physiology 09/2014; DOI:10.1104/pp.114.248633 · 7.39 Impact Factor

Full-text (2 Sources)

Download
73 Downloads
Available from
May 20, 2014