Effects of timing of drought stress on pomegranate seedlings (Punica granatum L. cv 'Atabaki') to exogenous spermidine and putrescine polyamines

Plant growth and productivity is adversely affected by nature's wrath in the form of various biotic and abiotic stress factors. Drought stress causes reductions in growth rate, along with a suite of metabolic changes. The initial reduction in shoot growth is probably due to hormonal signals generated by the roots. Different foliar treatments of spermidine and putrescine polyamines were applied to investigate the responses of commercial genotype of pomegranate, P. Atabaki to drought stress. Pomegranate cuttings were rooted and planted in the plastic bag contained 1: 1 sand: perlite medium and irrigated with complete Hoagland's solution immediately. For periodic irrigation 7, 15 and 21 respectively, each 7, 15 and 21 days one time and weight were given to the FC. 4 repeat for each treatment were selected, total dry period lasted 120 days. 72 h after drought treatments foliar treatments of spermidine and putrescine (0, 1 and 2 mM) were used, a non-ionic wetting agent (Rick 0.5 ml) was used in all treatments. Growth measurements (such as; the length of the main stem, the length and number of internodes, and leaf surface) were measured during the experiment. 120 days after treatments at harvest, concentration of Na, K, and Cl in root, apical and basal leaves of two genotypes were separately determined. In Atabaki genotype, increasing drought proportional to nail concentration, caused reduction in the length of stem, length and number of the internodes, and leaf surface. Application of polyamines led to increase in the rate of growth. On the other hand, reduction in the rate of growth was obtained from the application of drought stress at the levels higher than 70 mM. The tissue concentration of Na, and Cl was increased while the K/Na ratio decreased under the influence of high levels of drought stress. No significant differences were observed among two genotypes in Na, Cal, and K concentrations of roots, apical and basal leaves. The results obtained in this work indicated that foliar application of polyamine at different levels ameliorates the harmful effects of drought stress on growth of pomegranate.