Comparison between physiological characteristics and cold resistance of wild Poa root during the overwintering period in alpine regions in northern Tibet

The objective of this research was to investigate the physiological characteristics and cold resistance of wild Poa during the overwintering period, and to analyze the physiological adaptability of Poa under chilling stress in alpine regions in northern Tibet. The experimental materials included wild Poa litwinowiana, P. attenuata, P. crymophila, and a cultivated variety (Poa crymophila ‘Qinghai’). The soluble sugar (SS), soluble protein (SP), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) activities were measured in the field at an altitude of 4 512 m. The results showed that the overwintering rate of the 4 tested materials all reached 80%, and the overwintering rate of wild Poa was significantly higher (P < 0.05) than that of the cultivated variety. The contents of SS and MDA and the relative activities of SOD and CAT increased overall at first and then decreased from late autumn (September) until turning green the following year (May), reaching its maximum during the coldest month (January). The SP contents increased during the entire overwintering period. SOD and CAT of P. litwinowiana and P. attenuata in the coldest month were significantly higher (P < 0.05) than that of the others. Through the membership function analysis, it was found that the order of cold-resistance of the Poa tested was as follows: P. litwinowiana > P. attenuata > P. crymophila (wild varieties) > Poa crymophila ‘Qinghai’ (cultivated variety).