PHOTOSYNTHESIS AND GROWTH OF ERYTHRINA-VARIEGATA AS AFFECTED BY WATER-STRESS AND TRIACONTANOL

Erythrina variegata Lam. seedlings were grown under water stress (Psi = -3.2 MPa) and subsequently sprayed with triacontanol (Tria). Water s tress significantly reduced shoot growth rate, while roots continued t o grow. Content of chlorophyll (Chl) a decreased more than that of Chl b. Water stress also reduced photosynthetic activity of chloroplasts as measured by Chl fluorescence induction. Stress effect was identifie d at the oxidation site of photosystem (PS) 2 prior to the hydroxylami ne donating site and perhaps close to or after the diphenylcarbazide d onating site. The loss of O-2 evolving thylakoid polypeptides (33, 23, 17 kDa) and the large (55 kDa) and small (15 kDa) subunits of ribulos e-1,5-bisphosphate carboxylase (RuBPC) were found in water stressed se edlings. The reduction in RuBPC activity was accompanied by reduction of CO2 fixation and stomatal conductance. All photosynthetic parameter s were improved by Tria.