Do pH changes in the leaf apoplast contribute to rapid inhibition of leaf elongation rate by water stress? Comparison of stress responses induced by polyethylene glycol and down-regulation of root hydraulic conductivity
Ehlert C.,Montpellier SupAgro |
Plassard C.,Montpellier SupAgro |
Cookson S.J.,Umr1287 Institute Des Science Of La Vigne Et Du Vin |
Tardieu F.,Montpellier SupAgro |
Simonneau T.,Montpellier SupAgro
Plant, Cell and Environment | Year: 2011
We have dissected the influences of apoplastic pH and cell turgor on short-term responses of leaf growth to plant water status, by using a combination of a double-barrelled pH-selective microelectrodes and a cell pressure probe. These techniques were used, together with continuous measurements of leaf elongation rate (LER), in the (hidden) elongating zone of the leaves of intact maize plants while exposing roots to various treatments. Polyethylene glycol (PEG) reduced water availability to roots, while acid load and anoxia decreased root hydraulic conductivity. During the first 30min, acid load and anoxia induced moderate reductions in leaf growth and turgor, with no effect on leaf apoplastic pH. PEG stopped leaf growth, while turgor was only partially reduced. Rapid alkalinization of the apoplast, from pH 4.9±0.3 to pH 5.8±0.2 within 30min, may have participated to this rapid growth reduction. After 60min, leaf growth inhibition correlated well with turgor reduction across all treatments, supporting a growth limitation by hydraulics. We conclude that apoplastic alkalinization may transiently impair the control of leaf growth by cell turgor upon abrupt water stress, whereas direct hydraulic control of growth predominates under moderate conditions and after a 30-60min delay following imposition of water stress. © 2011 Blackwell Publishing Ltd.