将 49 份具有代表性的我国狗牙根〔Cynodon dactylon ( L.) Pers.〕种源的离体叶片进行模拟低温处理, 用电导法测其电导率, 将电导率拟合 Logistic 方程, 计算出狗牙根各种源叶片的半致死温度( LT50 ) 。 回归分析的结果表明:各种源的 LT50与其所在的经纬度呈显著的线性关系, 线性回归方程分别为 Y = -31.379 7 +0 .147 8X 和Y =-10 .798 2 -0 .142 0X 。 依据 LT50的变化, 可将这 49 份狗牙根种源分为 3 大类, 即低温敏感型( LT50 ≥-10℃) 、过渡型( -18℃<LT50 <-10℃) 和耐寒型( LT50≤-18 ℃) , 3 类狗牙根的分布具有一定的规律性。 对狗牙根的耐寒机理也进行了探讨。
 

Leaves of 49 accessions of Cynodon dactylon ( L.) Pers .were treated under simulate  low temperature in the freezer. Electrolyte leakage rate were measured and LT50 were calculated .The results of linear regressive analysis indicated that the LT50 vs .longitude and latitude are both proved to be notably linearly correlated .The equations are Y =-31 .379 7 +0 .147 8X and Y =-10 .798 2 -0 .142 0X . According to the LT50, three types of C .dactylon were determined, that is, low temperature sensitivity type ( LT50 ≥-10 ℃) , transition type ( -18 ℃<LT50 <-1 0 ℃) and low temperature tolerance type ( LT50 ≤-18 ℃) .And regularity is found in the distribution of the three types .This paper also inquired into the mechanism of low temperature tolerance reflected by LT50 .