Role of xanthophyll cycle-mediated photoprotection in <Emphasis Type="Italic">Arbutus unedo</Emphasis> plants exposed to water stress during the Mediterranean summer |
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Authors: | R Baraldi F Canaccini S Cortes F Magnani F Rapparini A Zamboni S Raddi |
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Institution: | (1) Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (C.S.I.C.), Apdo. 202, E-50080 Zaragoza, Spain |
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Abstract: | We analyzed the response of potted strawberry tree (Arbutus unedo L.) seedlings exposed to water stress by withholding water for 10 d (WS). Leaf water potential, net CO2 assimilation, and stomatal conductance decreased with increasing water deficit. A 30 % reduction of chlorophyll (Chl) content
in the antenna complexes was observed in WS-plants. Simultaneously, a decline of photochemical efficiency (Fv/Fm) occurred as a result of an excess of solar radiation energy when carbon assimilation was limited by stomata closure due
to soil water deficit. The non-photochemical quenching of Chl fluorescence (ΦNPQ) significantly increased, as well as the leaf contents of zeaxanthin (Z) and antheraxanthin (A) at the expense of violaxanthin
during the WS-period. Elevated predawn contents of de-epoxidized xanthophyll cycle components were associated with a sustained
lowering of predawn photosystem 2 efficiency; this suggested an engagement of Z+A in a state primed for energy dissipation.
Thus, the ability of strawberry trees to maintain the functionality of the xanthophyll cycle during the Mediterranean summer
is an efficient mechanism to prevent irreversible damages to the photosynthetic machinery through thermal energy dissipation
in the antenna and the reduction in photochemical efficiency. |
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