EFFECT OF WATER DEFICIT AND ABSCISIC ACID ON PHOTOSYNTHETIC AND ANTIOXIDANT METABOLISM IN SEEDLINGS OF Calophyllum brasiliense (Cambess.)

The aim of the present study was to evaluate the effect of different concentrations of abscisic acid (ABA) on photosynthetic metabolism and antioxidant enzyme activity in seedlings of Calophyllum brasiliense grown under water deficit. The experiment was carried out in a completely randomized design with six treatments: 1) daily irrigation without ABA (I 0 ABA); 2) daily irrigation + ABA 10 mu M (I 10 ABA); 3) daily irrigation + ABA 100 mu M (I 100 ABA); 4) suspension of daily irrigation without ABA (E 0 ABA); 5) suspension of daily irrigation + ABA 10 mu M (E 10 ABA); 6) suspension of daily irrigation + ABA 100 mu M (E 100 ABA). According to results, suspending irrigation decreased gas exchange and water potential, affecting negatively the functioning of the photochemical apparatus, increasing antioxidant enzyme activity. The decrease in stomatal conductance was accompanied by a decrease in photosynthetic and transpiration rates, but seedlings treated with 10 mu M ABA presented a higher photosynthetic rate than the remaining treatments under water deficit. Seedlings under water restriction showed recovery after reirrigation of all studied parameters until the end of the experiment, to values similar to those of control plants. Intermittent water defi cit decreased plant water status and gas exchange, and increases the antioxidant enzyme activity. Application of 10 mu M ABA minimizes the effects of water deficit and increases the antioxidant activity of superoxide dismutase (SOD) in the leaves in C. brasiliense seedlings and improve plant recovery after resuming irrigation, preserving the integrity and functioning of photosynthetic apparatus.