Priming bitter gourd seeds with selenium solution enhances germinability and antioxidative responses under sub-optimal temperature

Priming offers an effective means for counteracting sub-optimal temperature induced oxidative injury and raising seed performance in many crop species. In Taiwan, bitter gourd is frequently seeded when ambient temperatures are below the optimum. The objectives of the present study were to evaluate the effect of priming on germinability and antioxidative capacity in two bitter gourd cultivars germinated under 20 and 25 degreesC conditions. Sodium selenite was also added to the priming solution. Priming was achieved by moistening the seeds with 1, 2, 5, or 10 mg l(-1) sodium selenite solutions on germination paper at 25 degreesC for 48 h and then air-drying them to their original moisture levels. A sub-optimal temperature of 20 degreesC decreased seed performance by enhancing peroxidative injury. The sub-optimal temperature germinability was partially restored by priming the seeds with selenium solutions up to the 2 mg l(-1) level. The improved seed performances were linked to the priming-enhanced free radical and peroxide-scavenging activities linked to the ascorbate-glutathione cycle. However, glutathione peroxidase was the only enzyme showing positive response with increasing selenium level up to 10 mg l(-1), suggesting that this enzyme is selenium-inducible. The changes in germination and antioxidative activities in relation to selenium priming and sub-optimal temperature were similar for the two cultivars, despite differences in their germination performance and related antioxidative traits.