Effect of polyamines on physio-chemical and biochemical parameters of citrus rootstocks under NaCl stress

The present study was carried out to understand the role of polyamines on physiological and biochemical changes in citrus rootstocks grown under NaCl stress. Citrus is highly salt sensitive crop and salinity is a major constraint hindering its successful production. In general, soil salinisation with NaCl resulted in lowered photosynthetic activity, growth as well as RWC but increased MII. However, application of polyamines in different concentrations reduced the negative effects of NaCl stress and improved the overall growth of the plants. In this experiment, citrus rootstocks, viz., Jatti khatti, Rangpur lime, Attani-1 and Soh-sarkar were used. The maximum superoxidase dismutase (39.44 units 10 min(-1) mg(-1) of protein) and catalase (5.96 mu moles H2O2 reduced mg(-1) protein(-1)) activities were also noted in spermidine (0.75 mM) treated Rangpur lime rootstock under salt stress. The concentration of sodium and chloride in leaf tissue increased with NaCl treatment and maximum Na+ (2.21%) and Cl-(3.18%) concentrations were observed in Soh sarkar rootstock. Putrescine (0.75 mM) in citrus rootstock Jatti khatti and Soh sarkar and spermidine (0.75 mM) in Rangpur lime and Attani-1 showed better effects in reducing the negative effects of NaCl stress. It was observed that polyamines could improve the salinity tolerance of citrus rootstocks by regulating absorption and accumulation of ions and improving antioxidant enzyme activities.