Journal Article

Effects of drought on photosynthesis in Mediterranean plants grown under enhanced UV‐B radiation

Salvador Nogués and Neil R Baker

in Journal of Experimental Botany

Volume 51, issue 348, pages 1309-1317
Published in print July 2000 | ISSN: 0022-0957
Published online July 2000 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jexbot/51.348.1309
Effects of drought on photosynthesis in Mediterranean plants grown under enhanced UV‐B radiation

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The effects of drought on the photosynthetic characteristics of three Mediterranean plants (olive, Olea europea L.; rosemary, Rosmarinus officinalis L.; lavender, Lavandula stoechas L.) exposed to elevated UV‐B irradiation in a glasshouse were investigated over a period of weeks. Drought conditions were imposed on 2‐year‐old plants by withholding water. During the onset of water stress, analyses of the response of net carbon assimilation of leaves to their intercellular CO2 concentration were used to examine the potential limitations imposed by stomata, carboxylation velocity and capacity for regeneration of ribulose 1,5‐bisphosphate on photosynthesis. Measurements of chlorophyll fluorescence were used to determine changes in the efficiency of light utilization for electron transport, the occurrence of photoinhibition of photosystem II photochemistry and the possibility of stomatal patchiness across leaves. The first stages of water stress produced decreases in the light‐saturated rate of CO2 assimilation which were accompanied by decreases in the maximum carboxylation velocity and the capacity for regeneration of ribulose 1,5‐bisphosphate in the absence of any significant photodamage to photosystem II. Leaves of rosemary and lavender were more sensitive than those of olive during the first stages of the drought treatment and also exhibited increases in stomatal limitation. With increasing water stress, significant decreases in the maximum quantum efficiency of photosystem II photochemistry occurred in lavender and rosemary, and stomatal limitation was increased in olive. No indication of any heterogeneity of photosynthesis was found in any leaves. Drought treatment significantly decreased leaf area in all species, an important factor in drought‐induced decreases in photosynthetic productivity. Exposure of plants to elevated UV‐B radiation (0.47 W m−2) prior to and during the drought treatment had no significant effects on the growth or photosynthetic activities of the plants. Consequently, it is predicted that increasing UV‐B due to future stratospheric ozone depletion is unlikely to have any significant impact on the photosynthetic productivity of olive, lavender and rosemary in the field.

Keywords: Drought; Lavandula stoechas; Mediterranean vegetation; Olea europea; photosynthesis; Rosmarinus officinalis; ultraviolet‐B; water stress.; Asat, light‐saturated net CO2 assimilation rate; ci, intercellular CO2 concentration; E, daily plant evaporation rate; \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathit{F}_{m}^{{^\prime}}\) \end{document}, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathit{F}_{v}^{{^\prime}}\) \end{document} maximal and variable fluorescence yields in a light‐adapted state; gs, stomatal conductance; Fv/Fm, ratio of variable to maximal fluorescence yield in dark‐adapted leaves; Jmax, maximum potential rate of electron transport contributing to RuBP regeneration; l, stomatal limitation to Asat; RuBP, ribulose 1,5‐bisphosphate; RWC, relative leaf water content; Vc,max, maximum carboxylation velocity of Rubisco; ϕPSII, relative quantum efficiency of photosystem II photochemistry; ψw, leaf water potential

Journal Article.  6129 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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