The goal of this work was to assess the contribution of the aquaporin-mediated, transcellular (ATC) water pathway in different organs of a woody plant and under different water regimes (watered, drought). Moreover, we attempted to understand whether the role of aquaporins in embolism repair is significant in grapevine. In order to discriminate the aquaporin-mediated contribution to water transport, we used mercuric chloride as inhibitor of aquaporins . In a first experiment, we subjected Pinot noir plants grafted on K5BB to three watering regimes: normal irrigation, mild water stress, and severe stress. These treatments reflected on decreases of water potential of different plant organs and of root and shoot hydraulic conductivity, due to vessel embolizations. The ATC conductivity was not affected by severe stress while it was increased by mild stress in roots. No effects were observed in shoots, while in leaves ATC conductivity increased only in a near-isohydric genotype (sensitive to stress signals). HgCl2 treatment strongly inhibited the recovery of vessel embolizations in roots and in shoots, after either mild and severe stress. We assessed ATC conductivity in different stressed grape genotypes, tolerant or sensitive to water stress. ATC conductivity was larger in tolerant genotypes and was inversely related to the extent of vessel embolizations. Mild-stressed plants were grown with their root equally split between two containers, one watered and the other not watered. In these plants both an increase of ATC conductivity following water stress and an effect of ATC conductivity on recovery of embolisms could be demonstrated when HgCl2 was administered to the droughted half root. In the hypothesis that HgCl2 administered to this half root did not diffuse to the watered half root, this suggests that activation of ATC conductivity and its effect on recovery was localized in the droughted half root. We conclude from these experiments that mild (but not severe) water stress activates aquaporin density or function in grape and leaves. Proper functioning of aquaporins seems essential for embolism recovery in roots and in shoots. Our data, although not definitive, further suggest that aquaporin density or function may be activated by chemicals signals of stress in grape.
Aquaporin-mediated transcellular water transport in grape under water stress and rehydration
SCHUBERT, Andrea;LOVISOLO, Claudio
2004-01-01
Abstract
The goal of this work was to assess the contribution of the aquaporin-mediated, transcellular (ATC) water pathway in different organs of a woody plant and under different water regimes (watered, drought). Moreover, we attempted to understand whether the role of aquaporins in embolism repair is significant in grapevine. In order to discriminate the aquaporin-mediated contribution to water transport, we used mercuric chloride as inhibitor of aquaporins . In a first experiment, we subjected Pinot noir plants grafted on K5BB to three watering regimes: normal irrigation, mild water stress, and severe stress. These treatments reflected on decreases of water potential of different plant organs and of root and shoot hydraulic conductivity, due to vessel embolizations. The ATC conductivity was not affected by severe stress while it was increased by mild stress in roots. No effects were observed in shoots, while in leaves ATC conductivity increased only in a near-isohydric genotype (sensitive to stress signals). HgCl2 treatment strongly inhibited the recovery of vessel embolizations in roots and in shoots, after either mild and severe stress. We assessed ATC conductivity in different stressed grape genotypes, tolerant or sensitive to water stress. ATC conductivity was larger in tolerant genotypes and was inversely related to the extent of vessel embolizations. Mild-stressed plants were grown with their root equally split between two containers, one watered and the other not watered. In these plants both an increase of ATC conductivity following water stress and an effect of ATC conductivity on recovery of embolisms could be demonstrated when HgCl2 was administered to the droughted half root. In the hypothesis that HgCl2 administered to this half root did not diffuse to the watered half root, this suggests that activation of ATC conductivity and its effect on recovery was localized in the droughted half root. We conclude from these experiments that mild (but not severe) water stress activates aquaporin density or function in grape and leaves. Proper functioning of aquaporins seems essential for embolism recovery in roots and in shoots. Our data, although not definitive, further suggest that aquaporin density or function may be activated by chemicals signals of stress in grape.
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