Abstract

Different foliar treatments of spermidine and putrescine polyamines were applied to investigate the responses of the commercial genotype of pomegranate, P. Rabbab, to salinity. Pomegranate cuttings were rooted and planted in the plastic bag that contained sand and perlite medium in a ratio of 1:1 and irrigated with complete Hoagland’s solution immediately. Four salinity levels of irrigation water (0, 40, 80 and 120 mM NaCl) were used. At about 72 h after salinity treatments, foliar treatments of spermidine and putrescine (0, 1 and 2 mM) were used, while growth characteristics (that is, the length of the main stem, the length and number of internodes and the leaf surface) were measured during the experiment. At harvest, concentrations of Na, K and Cl in root, apical and basal leaves of two genotypes were separately determined 120 days after treatments. In Rabbab genotype, the increasing salinity proportional to NaCl concentration reduced the length of stem, the length and number of the internode and the leaf surface. There was an increase in the growth rate of salinity levels with an application of polyamines; although a decline in the growth rate occurred at salinity levels higher than 70 mM. With the increasing salinity level, the tissue concentration of Na and Cl increased, while the K/Na ratio decreased. No significant differences were observed among the two genotypes in Na, Cl and K concentrations of roots, apical and basal leaves. This result showed that the use of different degrees of exogenous polyamine can reduce the effects of stress on growth of pomegranate.

Key words: Pomegranate, polyamines, putrescine, salinity, spermidine.