Ameliorative effect of polyamines on the high temperature inhibition of in vitro pollen germination in tomato ( Lycopersicon esculentum Mill.)

Abstract

Effect of polyamines on in vitro pollen germination at high temperatures in tomato ( Lycopersicon esculentum Mill.) was investigated. Pollen germination and tube growth were significantly inhibited at 33°C and 35°C compared to those at 25°C. This inhibition was reversed by the addition of spermidine or spermine in the germination medium. Spermidine at 0.5 mM was slightly more effective than spermine at 0.05 mM. Spermidine at 0.05 and 0.5 mM and spermine at 0.05 mM slightly increased pollen germination rates at 25°C. Spermidine at 5 mM and spermine at 0.5 M were inhibitory to pollen germination, regardless of incubation temperatures. Spermidine also promoted germination of pollen grains incubated at 38°C for 1 and 3 h and then at 25°C for the rest of the 20 h incubation period. The effect was higher at 0.5 mM than at 0.05 mM. Treatment of spermidine to intact flowers 1 day before anthesis was also effective in ameliorating the high temperature inhibition of in vitro pollen germination on the polyamine-free medium. Here, the optimum concentration was 5 mM. These results demonstrate that polyamines can counteract the inhibitory effects of high temperature on pollen germination. They also suggest that the endogenous level of polyamines in germinating pollen grains is an important factor for the pollen germinability at high temperature.