[Evaluation of cold resistance of four wild Carex speices]

Four wild Carex speices (C. rigescens, C. lancifolia, C. leucochlora and C. humilis) collected from Mount Taishan were used as experimental materials. The adaption across the winter and physiological characteristics resistant to cold stress were investigated, semi-lethal temperature (LT₅₀) was calculated and fuzzy subordination method was used to generally evaluate the Carex resistant to cold stress. The results showed that 4 Carex species all survived in the winter safely and restored well to grow in the following spring. The green period of the species was between 260 d and 310 d, and percentage of the withered leaves was between 12% and 95%, the range of LT₅₀ was from -18.65 ℃ to -11.74 ℃. With intensifying cold stress, the contents of MDA, proline (Pro) and soluble protein increased at first and then decreased, while the soluble sugar content increased with the treatment time. C. rigescens with poor cold tolerance showed the early accumulation of MDA, Pro and soluble sugar. The value of soluble protein peaked at the late stage of low tempe-rature stress, and the Carex with stronger cold-resistance showed the smaller value. The SOD activity in the leaves of C. lancifolia was higher than that of the other three species in the beginning of treatments. The cold resistance of four Carex species was in order of C. lancifolia>C. leucochlora>C. humilis>C. rigescens.