Comparing physiological response of different strains of Gracilaria lemaneiformis to high temperature stress

The changes of physiological indices for 2 Gracilaria lemaneiformis strains (981 and 07-2) were studied at 23℃, 27℃ and 31 ℃, respectively. The results indicate that the relative growth rate of 07-2 increases at 23℃ and 27 ℃ while declines slightly at 31 ℃, and 981 shows a similar trend. The contents of chlorophyll and carotenoids in 07-2 are lower than those in 981 at 23 ℃ and 27 ℃ but become stable at 31℃. The content of phycocyanin in 07-2 is on the rise but without significant difference; the content of phycoerythrin is higher than that in 981, showing an ascendant trend. At 3 different temperatures, the photosynthetic pigments in 981 show no significant difference. The SOD activity in 07-2 shows an ascendant trend with significant difference while that in 981 increases slightly without significant difference. Therefore, 07-2 has better growth performance, photosynthetic pigment and antioxidant enzymes than 981, showing its advantage of high temperature resistance. Key words：Gracilaria lemaneiformis；strains；high temperature stress。