Effects of abscisic acid and benzyladenine on irrigated and non-irrigated grapevines

Abstract

Stomatal resistance, water potential, abscisic acid levels and shoot elongation were measured in irrigated and non-irrigated grapevines: ( Vitis vinifera L. ssp.) after application of water, abscisic acid (ABA) and benzyladenine (BA) 1. 1. A decline of the available soil water led to a decrease of water potential and to an increase of endogenous ABA and stomatal resistance. The changes in water potential and ABA levels due to water stress were much more distinct in ‘Riesling’ than in ‘Müller-Thurgau’ or ‘Bacchus’ cultivars. 2. 2. Application of water sprays to the leaves of irrigated and non-irrigated grapevines caused a decline of stomatal resistance and — in non-irrigated plants — an increase of water potential and shoot elongation, as well as a decrease of endogenous ABA. 3. 3. Application of BA delayed the increase of stomatal resistance in non-irrigated plants and decreased it in irrigated plants compared to the unsprayed, irrigated control. 4. 4. ABA applications hastened the increase of stomatal resistance in non-irrigated compared to irrigated plants and increased the values of water potential in non-irrigated plants. 5. 5. Neither BA nor ABA sprays affected the linear shoot elongation of the irrigated plants or the decline of shoot elongation due to water stress. 6. 6. In non-sprayed and in BA-treated, irrigated grapevines, stomatal resistance increased slightly in the late afternoon, while in ABA-treated plants an increase of stomatal resistance was observed throughout the day.