关键词: 葎草, 雌雄异株, 冬季, 水势, 光合作用

Abstract: In this research, responses to winter cooling in the wild dioecious climbing herb Humulus scandens were studied, with the aim of identifying any gender differences in the studied traits. On December 1, 10, 20, and 30 with day/night maximum/minimum temperatures of 15/10 ℃, 7/3 ℃, 12/7 ℃ and 4/1 ℃, designated T₁, T₂, T₃ and T₄, respectively were established over a period of natural seasonal cooling. The water potential, water content, chlorophyll content, photosynthetic parameters and a metabolic index of male and female plants were determined, and effects of cold on physiological metabolism of new mature stems and leaves of H. scandens were analyzed. The results showed: 1) In male plants, the leaf water potential of young leaves was less negative and the water content was higher than in female plants (P<0.05). 2) Chlorophyl a, chlorophyl a/b and chlorophyl (a+b) in the leaves of female plants were larger than in male plants (P<0.05). Cold significantly reduced chlorophyll content (P<0.05), and the rate of decline in male plants was faster than that of female plants, while the decline in mature leaves occurred earlier than in young leaves. 3) The intercellular CO₂ concentration (C_i) of both mature and young leaves of male plants were higher than those of female plants, while stomatal conductance (G_s) and photosynthetic rate (P_n) were lower than in female plants (P<0.05). The effect of seasonal temperature decrease on C_i, G_s and P_n was greater than the difference between sexes (P<0.05). Cold decreased G_s and P_n, and increased C_i, and the effect of cold on male plants was greater than that on female plants. At T₃, P_n of male plants was negative while female plants was positive. At T₄, the actual P_n values of male and female plants were both negative, but the potential P_n of female plants was greater than that of male plants. 4) The content of soluble sugar (SS) in the leaves and young stems of male plants was higher than that in female plants, but the contents of free proline (Pro) in stems and leaves, and of SS in mature stems were lower than those in female plants (P<0.05). There were significant gender differences between mature and young stem-leaves in the levels of cold resistance metabolites. At T₂, the content of SS and Pro in the mature and young stem-leaves of male and female plants all increased (P<0.05). At T₃, the content of SS and Pro in the mature leaves and young stems of male plants decreased more than those in female plants. At T₄, the content of SS and Pro in the mature stems of male plants decreased and those in the female plants increased. In summary, there were significant gender differences in the effects of cold on leaf water potential, stem and leaf water content, photosynthetic parameters and cold resistance metabolite content of H. scandens. Female plants had a stronger physiological adaptation to cold stress than male plants.

Key words: Humulus scandens, dioecious, winter, water potential, photosynthesis