Effect of spermidine on cold tolerance of cucumber seeds in completing germination stage

To investigate the effect of spermidine on the cold tolerance of cucumber cultivar ‘Rashid’ in completing germination stage, an experiment was conducted using a completely randomized design with 4 replications and 4 treatments consist of different concentrations of spermidine (0, 0.1, 0.5 and 1 mM) in Incubator of College of Agriculture, Isfahan University of Technology. So seeds were exposed to 20°C for two days and then treated with spermidine, the remaining 13 days they were kept at 15, 13, 11 or 9°C. To compare the effects of temperature and its interactions with the hormone, data of four experiments analyzed as a split-plot experiment (four different temperatures as four main plots and four spermidine concentrations as four subplots). At the end of each experiment characteristics consist of length of shoot and root, fresh and dry weight of shoot and root and ion leakage of shoot and root were measured. The findings of this study showed that the application of spermidine in low concentrations was more effective than high concentrations for controlling chilling injury. Also in most cases, concentrations of more than 0.5 mM spermidine demonstrated inhibitory effect on measured characteristics. By reducing the temperature in this stage, most of the growth characteristics reduced, significantly. Significant interactions between hormone concentrations and temperatures were observed on shoot and root length, and root fresh weight. Overall, 0.5 mM spermidine is recommended to reduce the negative effects of chilling injury on the germination of cucumber seeds.