Abstract

In this study, we investigated differences between cool-season and warm season grasses when exposed to heat stress. The results show that Kentucky blue seed germination rate was the highest at 25^oC (40-50%), decreased significantly at 30^oC (23-30%) and dropped to 0 at 40^oC. For the Bermuda cultivars, seed germination rate was two fold higher at 30^oC then 25^oC, and reached the highest at 40^oC. The cool season perennial rye and Bent grass seeds germinated well between 25 and 30^oC. Their germination rate was significantly lower at 40^oC. After exposure to 38^oC for 2 d, the chlorophyll content decreased significantly for Bermuda cultivars, remained stable for Bent grass and perennial rye, and increased to the greatest extentfor Kentucky blue. Leaf soluble protein contents increased significantly for Kentucky Blue, but remained stable for most of the other cultivars. Western blot with Hsp70 and dehydrin antibodies identified that the Bermuda cultivars had a dynamic changes in the profile of the heat and dehydration stress-related proteins. No similar changes were detected in Kenblue cultivars. High temperature induced dehydrin homolog proteins, but not the Hsp 70 in Perennial rye and Bent grass cultivars. Findings from this research can be used to differentiate cool season and warm season grass cultivars in terms of germination and survival ability under high temperature.

Key words:  seed germination, chlorophyll content, leaf soluble protein, heat shock protein, dehydrin protein.