Phytochrome A increases tolerance to high evaporative demand

IFEVA-CONICET, Facultad de Agronomía, Universidad de Buenos Aires, Buenos Aires, Argentina IBAM-CONICET, Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo, Mendoza, Argentina Instituto de Ciencias Básicas, Universidad Nacional de Cuyo, Mendoza, Argentina Laboratorio de Anatomía Vegetal, Cátedra de Botánica Agrícola, Facultad de Agronomía, Universidad de Buenos Aires, Buenos Aires, Argentina.
Physiologia Plantarum (Impact Factor: 3.26). 10/2012; 146(2):228. DOI: 10.1111/j.1399-3054.2012.01625.x

ABSTRACT Stresses resulting from high transpiration demand induce adjustments in plants that lead to reductions of water loss. These adjustments, including changes in water absorption, transport and/or loss by transpiration, are crucial to normal plant development. Tomato wild type (WT) and phytochrome A mutant plants, fri1-1, were exposed to either low or high transpiration demand conditions and several morphological and physiological changes were measured during stressing conditions. Mutant plants rapidly wilted compared to WT plants after exposure to high evaporative demand. Root size and hydraulic conductivity did not show significant differences between genotypes, suggesting that water absorption and transport through this organ could not explain the observed phenotype. Moreover, stomata density was similar between genotypes, whereas transpiration and stomata conductance were both lower in mutant than in wild type plants. This was accompanied by a lower stem specific hydraulic conductivity in mutant plants than in wild type, which was associated to smaller xylem vessel number and transversal area in fri1-1 plants, producing a reduction in water supply to the leaves, rapidly reaching wilting under high evaporative demand. Phytochrome A signaling might facilitate the adjustment to environments differing widely in water evaporative demand in part through the modulation of xylem dimensions.

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