Changes in ecophysiological performances in grapevines overexpressing the aquaporin VvPIP2;4.

Grapevines transformed to over-express an aquaporin gene were tested under both irrigated and droughted conditions. We measured: gas exchanges by Infra Red Gas Analyzer, root hydraulic conductivity (Khroot) by High Pressure Flow Meter (HPFM), and embolism formation and recovery in petioles by HPFM differential application as influenced by transient flushing pressure. In irrigated conditions, assimilation, stomatal conductance, transpiration and leaf surface were significantly higher in transgenic plants than in wild types. Higher stomatal conductance of transgenic plants was related to a higher Khroot. Transgenic plants embolized upon environmental conditions not causing embolism in wild types, probably in relation to transpiration levels higher in transgenic lines. Overexpression of VvPIP2;4 ameliorated growth performances by modifying water metabolism under no water restrictions, whereas did not induce a drought stress resistance. Transcript level of the endogenous VvPIP2;4 in transgenic lines, analyzed by RT-PCR assay, suggests a molecular compensation mechanism related to ecophysiological behavior.