No abstract

Studying changes in partitioning of dry matter and nonstructural carbohydrates (NSC) content in both aboveground and underground perennial tissues in drought-affected grapevines could provide insights into plant response and carbon allocation strategies during stress periods. The analysis of soluble NSC and starch content in leaf petioles, due to their role in hydraulic segmentation, should also be considered. In the present research, these aspects have been investigated in Merlot grapevines grown in pots and subjected to progressive and increasing soil dehydration, and in well-irrigated vines. Drought conditions caused drastic reduction of shoot elongation and total plant leaf area development in favor of a greater biomass allocation and partitioning towards roots, where most of the NSC reserves were also conserved. Dry matter content of the perennial organs increased in stressed vines due to growth reduction, allocation of carbon reserves and possible anatomical modifications. Vines subjected to drought showed a higher NSC content in petioles, supporting the hypothesis that they are involved as compatible solutes in osmotic adjustments.

No abstract

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 (Ψleaf) measurements and the minimum equilibration time for stem water potential (Ψstem) determination, taking 24 h leaf cover as control. In ‘Pinot gris’, Ψleaf 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 Ψleaf. In Es, the minimum Ψstem equilibration was 1 h for ‘Refošk’ 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.