Effect of exogenous polyamines and inhibitors of polyamine biosynthesis on growth and free polyamine contents of embryogenic Scots pine callus

Effects of the exogenously added polyamines putrescine, spermidine and spermine and the inhibitors of polyamine biosynthesis, methylglyoxal bis(guanylhydrazone) (MGBG) and dicyclohexylamine (DCHA), in the DCR medium on the endogenous polyamine levels and growth of embryogenic callus of Scots pine (Pinus sylvestris L.) were studied. With polyamine treatments the endogenous putrescine level was significantly affected only by 10 mu mol/L spermidine, which decreased the putrescine. Other polyamine treatments did not have an effect on the putrescine level. Endogenous spermidine or spermine levels were not significantly affected by exogenous polyamines, although lower spermine concentrations were found in callus tissues with all polyamine supplements. DCHA significantly reduced the endogenous putrescine level but nor the spermidine or spermine levels. The highest concentration of MGBG (5 mmol/L), but not the lower ones (0.1 and 1 mmol/L), reduced putrescine, spermidine and spermine levels. The callus tissues cultured with exogenous polyamines or inhibitors showed a positive correlation between endogenous putrescine and the relative growth rate (R-G) The correlation was also positive between the endogenous spermidine and R-G, but no correlation was found between the endogenous spermine and R-G. Exogenous polyamines did not affect: the growth of the callus tissues. All DCHA treatments (0.1, 1.0 and 5 mmol/L) inhibited the growth of the calli, whereas MGBG inhibited the growth only with the highest concentration (5 mmol/L).