Water stress induces different levels of photosynthesis and electron transport rate regulation in grapevines

Abstract

Diurnal time courses of chlorophyll fluorescence and gasexchange rates were measured in young potted grapevines (Vitis vinifera L. cv. Tempranillo) subjected to different conditions of water supply under Mediterranean summer conditions. The irrigated plants exhibited typical diurnal patterns for all measured parameters, showing a correspondence between electron transport rate, net CO 2 assimilation and stomatal conductance. Mild decreases in soil-water availability led to different degrees of down-regulation of photosynthesis and increased nonphotochemical quenching of chlorophyll fluorescence. A good correspondence between electron transport rate and CO 2 assimilation was still maintained, suggesting a coregulation of both photosynthetic processes. In contrast, a severe water deficit induced a drastic down-regulation of photosynthesis and breakage of the above-mentioned link. Both midday net CO 2 assimilation and electron transport rate significantly correlated with pre-dawn water potential (Ψ PD ) (r 2 = 0·65 and r 2 = 0·92, P < 0·001, respectively). However, when field data were analysed, the relationship between electron transport rate and Ψ PD was not maintained, although net CO 2 assimilation was similarly correlated with Ψ PD . Interestingly, the steady-state chlorophyll fluorescence yield was a good indicator of plant water stress.Key-words: Vitis vinifera L.; Vitaceae; chlorophyll fluorescence; electron transport rate; grapevines; photosynthesis; water stress.Abbreviations: A, net CO 2 assimilation rate; E, leaf transpiration; ETR, electron transport rate; F s , fluorescence yield at steady state; F m and F m ', maximal fluorescence levels when all PSII reaction centres are closed in dark-and light-acclimated leaves, respectively; F o and F o ', initial fluorescence levels when all PSII reaction centres are closed in dark-and light-acclimated leaves, respectively; F v /F m , efficiency of excitation capture by open PSII in dark-adapted leaves; ∆F/F m ', actual photochemical efficiency of PSII; g, stomatal conductance; NPQ, non-photochemical quenching of chlorophyll fluorescence; PPFD, photosynthetic photon flux density; Ψ PD and Ψ MD , leaf water potential at pre-dawn and midday, respectively; Rl, estimated photorespiration rate; I 1 and I 2 , Irrigation treatments; R, Recovery treatment; D 1 and D 2 , drought treatments; HD 1 and HD 2 , hard drought treatments. INTRODUCTIONDrought is considered to be a predominant factor both for determining the global geographic distribution of vegetation and for restricting crop yields in agriculture (Schulze 1986). Furthermore, water stress is a limiting factor for a wide range of physiological processes in plants (Cornic 1994;McDonald & Davies 1996) There is much evidence that water stress per se does not cause reductions in primary events of photosynthesis, i.e. PSII efficiency (Genty, Briantais & Vieira da Silva 1987;Cornic et al. 1989). However, water stress is often accompanied (particularly under Mediterranean conditions) by other limiting factors such...

Partial rootzone drying: regulation of stomatal aperture and carbon assimilation in field-grown grapevines (Vitis vinifera cv. Moscatel)

“…This results in the reduction of the quantum yield of PSII photochemistry but allows the maintenance of a balance with electron flow requirements for carbon metabolism (Weis and Berry 1987;Krause and Weis 1991). Furthermore, the increased ETR/A ratio also observed in NI vines indicates that at least some of the electrons are not used directly in CO 2 assimilation but rather in other processes such as photorespiration, which has been reported to increase under drought (Leegood 1995;Flexas et al 1999b). These responses in grapevines play an important role in the regulation between the photochemical and the carbon assimilation reactions under water stress, as in other species adapted to Mediterranean climates (Quick et al 1992).…”

Rapid plant rehydration initiates permanent and adverse changes in the photosynthetic apparatus of triticale

“…So far, numerous papers have been published on different mechanisms of plant acclimation to soil drought and on their role in the selection of cultivars or genotypes resistant to soil water deficit (Flexas et al 1999(Flexas et al , 2006Escalona et al 2000;Flexas and Medrano 2002;Hura et al 2007aHura et al , 2009aHura et al , b, c, 2011Hura et al , 2012Grzesiak et al 2010;Rollins et al 2013;Nolf et al 2014;Borrell et al 2014). However, very few studies investigated the problem of adverse functional changes brought about by the rehydration stage (Oliver et al 1998;Hura et al 2009a).…”

Factores abióticos involucrados en la facilitación entre leñosas y suculentas en el altiplano mexicano.

“…Por otra parte, en Opuntia jaliscana la humedad baja fue la que más disminuyó la TTE. Se conoce que el estrés hídrico aumenta la competencia por el uso de los electrones, entre el proceso de fotorespiración y la asimilación de CO 2 (Flexas et al, 1999); estos resultados coinciden con los encontrados por Flexas et al (2002) en plantas C 3 en condiciones de campo.…”