Best Procedures for Leaf and Stem Water Potential Measurements in Grapevine: Cultivar and Water Status Matter

The pressure chamber is the most used tool for plant water status monitoring. However, species/cultivar and seasonal effects on protocols for reliable water potential determination have not been properly tested. In four grapevine cultivars and two times of the season (early season, Es; late season, Ls, under moderate drought), we assessed the maximum sample storage time before leaf water potential (& psi;(leaf)) measurements and the minimum equilibration time for stem water potential (& psi;(stem)) determination, taking 24 h leaf cover as control. In 'Pinot gris', & psi;(leaf) already decreased after 1 h leaf storage in both campaigns, dropping by 0.4/0.5 MPa after 3 h, while in 'Refosk', it decreased by 0.1 MPa after 1 and 2 h in Es and Ls, respectively. In 'Merlot' and 'Merlot Kanthus', even 3 h storage did not affect & psi;(leaf). In Es, the minimum & psi;(stem) equilibration was 1 h for 'Refosk' and 10 min for 'Pinot gris' and 'Merlot'. In Ls, 'Merlot Kanthus' required more than 2 h equilibration, while 1 h to 10 min was sufficient for the other cultivars. The observed cultivar and seasonal differences indicate that the proposed tests should be routinely performed prior to experiments to define ad hoc procedures for water status determination.

Automated summary

The pressure chamber is commonly used for plant water status monitoring, but its protocols for water potential determination have not been properly tested in different grapevine cultivars and seasons. The storage time for leaf water potential measurements and equilibration time for stem water potential determination were evaluated in four grapevine cultivars under moderate drought conditions. The results showed that the storage time and equilibration time varied among cultivars and seasons, suggesting the need for specific procedures for water status determination in different conditions.