Influence of a drying cycle on post-drought xylem sap abscisic acid and stomatal responses in young temperate deciduous angiosperms

Post-drought patterns of water relations and gas exchange were studied in relation to xylem sap abscisic acid (ABA) concentration during recovery for young plants of five woody species. The potential role of xylem sap [ABA] in these responses was the object of study. Potted plants were allowed to deplete soil water and then were rewatered. At peak drought and during recovery, predawn and midday leaf water potential (Psi(l)), stomatal conductance (g(s)), and xylem sap [ABA] were measured. Water potentials recovered rapidly after rewatering but stomatal re-opening was delayed. Xylem sap [ABA] was elevated early in recovery and might have affected stomatal opening, but after 1 d at high soil water content [ABA] in recovering plants was equal to or lower than in control plants. Stomata appeared to be more sensitive to xylem sap [ABA] in recovering than droughted plants. Xylem sap [ABA] may play some role in delayed recovery of stomatal opening after drought, but may not completely explain the responses.