Polyamines reduce salt-induced oxidative damage by increasing the activities of antioxidant enzymes and decreasing lipid peroxidation in Virginia pine

Polyamines play an important role in the plant response to adverse environmental conditions including salt and osmotic stresses. In this investigation, the responses of polyamines to salt-induced oxidative stress were studied in callus cultures and plantlets in Virginia pine (Pinus virginiana Mill.). Our results demonstrated that polyamines reduce salt-induced oxidative damage by increasing the activities of antioxidant enzymes and decreasing lipid peroxidation. Among different polyamines used in this study, putrescine (Put) is more effective in increasing the activities of ascorbate peroxidase (APOX), glutathione reductase (GR), and superoxide dismutase (SOD), reducing the activities of acid phosphatase and V-type H+-ATPase, and decreasing lipid peroxidation in Virginia pine, compared to both spermidine (Spd) and spermine (Spm). When 2.1 mM Put, Spd, and Spm were separately added to the medium, higher diamine oxidase (DAO) and polyamine oxidase (PAO) activities were observed in callus cultures and plantlets, compared to the concentrations of 0.7 and 1.4 mM. The activities of these two enzymes produce hydrogen peroxide (H₂O₂), which may act in structural defense as a signal molecule and decreasing the protection of polyamines against salt-induced oxidative damage in Virginia pine.