effects of antioxidants on photosynthetic characteristics and vegetative growth in olive (olea europaea l. cv. zard) under salinity stress

the production of oxygen radicals in plants under salinity stress conditions in an the important factor for a diminishing of a photosynthesis and a cause fir a decrease in later vegetative growth. in order to study the effects of antioxidants and salinity stress on photosynthetic characteristics and growth in olive, an experiment was conducted in the research greenhouse of tabriz university in 2007. in this experiment ascorbic acid (2mm) and reduced glutathione (3mm) as well as control combined, with two nacl concentrations, were factorially applied on one year old olive plants. the experiment was carried out as a complately randomized block design with four replications. results indicated that ascorbic acid had a great effect on photosynthesis in the non-saline treatment in comparison with others. exogenous application of ascorbic acid caused an increase in stomatal conductance, respiration, chlorophyll and such vegetative traits as leaf area ratio and leaf weight ratio. on the other hand, this treatment led to decrease in leaf water content, specific leaf area and leaf water content per unit area. some such traits as net photosynthesis, stomatal conductance, respiration, leaf area ratio, chlorophyll shoot water content, shoot water content, leaf weight ratio and peroxidase activity were significantly decreased in salinity treatment. other traits as well (leaf water content, specific leaf area and leaf water content per unit area) were increased in the salinity treatment with regard to these results, ascorbic acid was shown to exert positive effects in improvement of photosynthesis and growth of olive under saline and non-saline conditions in comparison with reduced glutathione, and with control.