Abscisic acid and its metabolites are involved in drought tolerance in four native species of Patagonian semiarid shrublands (Argentina)

Drought is the main stress that affects growth of native species of Patagonian Monte. Physiological and biochemical traits with functional roles in adaptation to drought are still scarce in native species. The aim of this study was to evaluate changes in dry matter content and abscisic acid (ABA) and its metabolites (phaseic acid-PA, dihydrophaseic acid-DPA, ABA conjugated with glucose-ABA-GE) level in green leaves and fine roots of four native species during contrasting seasons regarding water availability. Results show that grasses had higher leaf dry matter content (LDMC) and root dry matter content (RDMC) than Lycium chilense shrub and LDMC decreased during autumn in Larrea divaricata. In green leaves, there was an interaction between species and seasons for ABA and PA contents. L. divaricata had high ABA content during spring and low ABA content during autumn; while L. chilense showed the opposite pattern. During spring, drought tolerant species had high PA content while drought avoidant species had low PA content, and during autumn these species showed the opposite pattern. ABA-GE content was highest in L. chilense green leaves. In fine roots, ABA content was highest in L. divaricata and during spring PA was higher in L. divaricata than P. ligularis and L. chilense. PA was the only metabolite that decreased in L. divaricata during autumn. Results showed that ABA homeostasis maintains the functioning of different life forms with different drought resistance strategies in Patagonia semiarid shrublands. In green leaves of the drought avoidant L. chilense shrub, the ABA conjugation pathway was active in both seasons. During spring, the most drought tolerant L. divaricata showed highest activation of ABA synthesis and ABA oxidation pathways. During autumn L. chilense showed highest activation of ABA synthesis and together with P. ligularis showed active the ABA oxidation pathway.