Study on the Key Period of Germination of Different Cotton Varieties at Low Temperature Based on Principal Component Analysis

In order to determine the critical period of hazard to cotton seed germination, the cotton varieties Xinluzhong 46, Xinluzao 57, Xinluzao 74 and Xinluzao 82 were used as materials to investigate the seed vigor and radicle growth of the four cotton varieties during seed germination under 12 ℃, with 25 ℃ as control. The results showed that low temperature treatment at 12 ℃ could reduce seed vigor and inhibit radicle growth of cotton. There were differences in low temperature tolerance among different varieties, and the cotton variety Xinluzao 57 showed the strongest low temperature tolerance. There were positive correlations among the 7 indexes, the correlation between germination index and vitality index, radicle fresh weight and radicle dry weight was the highest while the correlation between germination potential and radicle length, germination index and radicle length was the least. The comprehensive scores of principal components analysis of different cotton varieties and different treatments were T 2＜T 3＜T 4＜T 1＜T 5＜T 6＜T 7, which implied the second and third day of germination of cotton seed might be the critical period for low temperature damage.