Abscisic acid-mediated stomatal closure and antioxidant defenses in Jatropha curcas L. seedlings submitted to moderate water deficit

The objective of this research was to evaluate the biochemical changes in leaves from different genotypes of J. curcas in order to extend knowledge regarding the mechanisms of tolerance to water deficit and its variation in different genotypes. Potted plants of three genotypes (CNPAE 126, 137 and 139) were cultivated under water deficit conditions for 66 days. Two watering regimes, as measured by the percentage of field capacity (FC), were imposed: Control plants (100% FC) and plants submitted to water deficit (70% FC). After 66 days, no significant effects of treatment and of genotype on leaf water potential (Ψw) were observed. While the water deficit treatment led to significant increments in foliar concentrations of proline and soluble sugars in all genotypes, no significant effects of genotype or treatment on K+ concentration were detected. In addition, significant differences among treatments and genotypes in the activity of antioxidant enzymes (SOD, CAT and POD) and [ABA] in leaf and root were demonstrated. The genotypes exhibited an effective mechanism of response against the effects of water deficit, involving accumulation of compatible osmolytes, and increased antioxidants enzymes and ABA. Taken together, that results configure a strategy for maintenance of leaf hydration under moderate water deficit. Key words: Abiotic stress, antioxidant enzymes, compatible osmolytes, Euphorbiaceae, gas exchange.