Abstract:

Under natural and artificial low temperature stress, the relative electric conductivity, SOD activity and soluble sugar content of varieties of ‘Zhuliu’ No.3 and ‘Zhuliu’ No.5 were determined, with hankow willow (Salix matsudana) served as control. The cold resistance of the plants was comprehensively evaluated by the method of subordinate function with the measured data. Results showed that under natural low temperature stress, relative electric conductivity, SOD activity and soluble sugar content of selected twigs first increased and then declined with the decrease and increase of natural temperature. Under artificial low temperature stress, relative electric conductivity of the twigs increased with the decrease of temperature, SOD activity and soluble sugar content presented first increased and then dropped. The semi-lethal temperature of hankow willow, ‘Zhuliu’ No.5, and ‘Zhuliu’ No.3 was-42.87,-37.27, and-31.60 ℃,respectively, and the cold resistance of the varieties was as the follows: hankow willow>‘Zhuliu’ No.5>‘Zhuliu’ No.3. The ‘Zhuliu’ No.5, with relatively stronger cold resistance, grew well and overwintered successfully in 2011 in Harbin, Daqing, Qiqihar, and Heihe of Heilongjiang Province. The study showed that ‘Zhuliu’ No.5 could be applied to the region where winter temperature is above-37.27 ℃ through introduction and overwintering acclimation at the seedling stage.

Key words: Zhuliu'variety, cold resistance, relative electric conductivity, SOD, soluble sugar