فهرست نشریات علمی دسترسی آزاد ایران

The Effect of salinity (50 mM NaCl) and exogenous putresine and spermidine (0.5 mM) on growth and photosynthesis of tobacco (Nicotiana rustica L) plants were studied in hydroponic medium. Salinity caused reduction of plants growth. Application of putresine increased dry weight of control plants while exogenous spermidine decreased it. Exogenous putresine ameliorated salinity stress only in roots, but spermidine exerted this effect on both shoot and roots. In the absence of polyamines, salinity decreased chlorophyll a significantly and chlorophyll a/b ratio as well but application of polyamines increased these parameters. Salinity caused reduction of net CO2 assimilation rate. Under control conditions, polyamines reduced net CO2 assimilation ratebut the rate was increased in the treated plants. Total leaf phenolics was not influence by salinity, but application of putresine in salinity conditions reduced phenolic contents and of spermidine increased total phenolics of leaves. The activities of leaf phenylalanine ammonia lyase and polyphenol oxidase decreased in salinized plants, while exogenous polyamines increase and decrease in their activity, respectively. Growth impairment due to exogenous spermidine in control plants could be resulted from reduction of photosynthesis and increase of leaf phenolics. In spite of a negative effect of exogenous spermidine on growth of control plants, application of both polyamines ameliorated salinity stress. This effect was likely mediated by the improvement of leaf photochemical parameters and increase of CO2 assimilation. Phenolics metabolism was greatly influenced by exogenous polyamines, however, no correlation was found between ameliorative effect of polyamines and changes in the phenolics metabolism.