VARIATIONS IN ABSCISIC-ACID, INDOLE-3-ACETIC-ACID AND ZEATIN RIBOSIDECONCENTRATIONS IN 2 MEDITERRANEAN SHRUBS SUBJECTED TO WATER-STRESS

Water stress induced an increase in endogenous concentrations of ABA i n Lavandula stoechas L. plants to 13100 pmol ABA g(-1) FW, which may c ontribute to the maintenance of water relations between the second and the third day of water stress treatment. After the third day, a sharp decrease in ABA levels was observed to 2630 pmol ABA g(-1) FW, togeth er with a decrease in water content and water potential and a loss of plant response to water stress. Water deficit did not induce an increa se in endogenous ABA concentration, which remained at 514 pmol ABA g(- 1) FW in Rosmarinus officinalis L., which is more sclerophyllous than L. stoechas. Nevertheless, the relative water content of Rosmarinus of ficinalis L. after seven days of water stress decreased more than 40% and psi reached values of -3.2 MPa. R. officinalis showed lower levels of ABA, but significantly higher levels of IAA and ZR than L. stoecha s (4 times and 6 times respectively in well watered-plants), The incre ase in ABA levels is not a common mechanism in these two Mediterranean shrubs which survive under water stress conditions.