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

Abstract

The aim of the present study was to evaluate the effect of different concentrations of abscisic acidon photosynthetic metabolism and antioxidant enzyme activity in seedlings of Calophyllum brasiliense Cambess. grown under water deficit. A completely randomized design was used, with six treatments: 1) daily irrigation without ABA (I 0 ABA); 2) daily irrigation + ABA 10 µM (I 10 ABA); 3) daily irrigation + ABA 100 µM (I 100 ABA); 4) suspension ofdaily irrigation without ABA (E 0 ABA); 5) suspension ofdaily irrigation + ABA 10 µM (E 10 ABA); 6) suspension ofdaily irrigation + ABA 100 µM (E 100 ABA). Suspending irrigationdecreasedgas exchange and water potential, negativelyaffected the functioningof thephotochemical apparatus, and increased antioxidant enzyme activity. The decrease in stomatal conductance was accompanied by a decrease in photosynthetic and transpiration rates, but seedlings treated with 10 µM ABA presented a higherphotosynthetic ratethan the remaining treatments under water deficit. Antioxidantenzyme activity during suspension ofirrigation varied with the enzyme, ABAconcentration,and plant part. The application of 10 µM ABAmitigated the effects of drought stress and improved plant recovery after reirrigation, preserving the integrity and functioning of the photosynthetic apparatus. Seedlings under water restriction showed recovery of all studied parametersuntil the end of the experiment,to values similar to those of control plants.