Plant cell transmembrane water transport, and in particular the contribution of aquaporin-mediated transcellular (ATC) pathway to that process, can play profound roles on drought defense mechanisms. Our work is focused on the understanding of the level where transmembrane water transport acts in such mechanisms at the whole-plant scale. In order to investigate this topic, several genotypes of Vitis spp. were cultivated in pots, watered (W) or drought-stressed (S), and hydraulic conductance of root, shoot and leaf were measured. To uncouple hydraulic and not-hydraulic drought signals from root to shoot, an additional water stress treatment was imposed to split-rooted grapevines by irrigating only half of the root (half stress, HS). To discriminate the ATC-path contribution, roots, shoots and leaves were treated in vivo with 0.5, 0.5, and 0.05 mM HgCl2, respectively. To quantify embolism occurrence, hydraulic measurements were performed either before or after a pressure flushing (200 kPa) designed to eject out embolisms from shoots and roots. When grapevines were fully watered (PSIleaf = -0.37 MPa), the ATC-pathway contribution on hydraulic conductance was about 20% in root, 16% in shoot, and 45% in leaf. On S plants (PSIleaf = -0.95 MPa), whose roots embolized twice and shoots twenty times as much as W controls, the ATC-pathway contribution was 52%, 6% and 37%, respectively, suggesting an up-regulation of expression and/or activity of mercury-sensitive aquaporins under drought at the root level, and a down-regulation at both shoot and leaf levels. On HS plants (PSIleaf = -0.41 MPa), which did not embolize more than W controls, the ATC pathway contributed 45% to water transport in the root and 10% in the shoot. Even if both leaf water potential and xylem embolization of HS plants did not differ from watered controls, the activation of the ATC pathway was similar to plants under water stress, suggesting that aquaporins are up regulated upon drought via a non hydraulic signal.
Contribution of mercury-sensitive aquaporins to hydraulic conductance in roots, shoots and leaves of droughted Vitis spp
LOVISOLO, Claudio;TRAMONTINI, SARA VALENTINA;SCHUBERT, Andrea
2004-01-01
Abstract
Plant cell transmembrane water transport, and in particular the contribution of aquaporin-mediated transcellular (ATC) pathway to that process, can play profound roles on drought defense mechanisms. Our work is focused on the understanding of the level where transmembrane water transport acts in such mechanisms at the whole-plant scale. In order to investigate this topic, several genotypes of Vitis spp. were cultivated in pots, watered (W) or drought-stressed (S), and hydraulic conductance of root, shoot and leaf were measured. To uncouple hydraulic and not-hydraulic drought signals from root to shoot, an additional water stress treatment was imposed to split-rooted grapevines by irrigating only half of the root (half stress, HS). To discriminate the ATC-path contribution, roots, shoots and leaves were treated in vivo with 0.5, 0.5, and 0.05 mM HgCl2, respectively. To quantify embolism occurrence, hydraulic measurements were performed either before or after a pressure flushing (200 kPa) designed to eject out embolisms from shoots and roots. When grapevines were fully watered (PSIleaf = -0.37 MPa), the ATC-pathway contribution on hydraulic conductance was about 20% in root, 16% in shoot, and 45% in leaf. On S plants (PSIleaf = -0.95 MPa), whose roots embolized twice and shoots twenty times as much as W controls, the ATC-pathway contribution was 52%, 6% and 37%, respectively, suggesting an up-regulation of expression and/or activity of mercury-sensitive aquaporins under drought at the root level, and a down-regulation at both shoot and leaf levels. On HS plants (PSIleaf = -0.41 MPa), which did not embolize more than W controls, the ATC pathway contributed 45% to water transport in the root and 10% in the shoot. Even if both leaf water potential and xylem embolization of HS plants did not differ from watered controls, the activation of the ATC pathway was similar to plants under water stress, suggesting that aquaporins are up regulated upon drought via a non hydraulic signal.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
