Study On Photosynthetic And Physiological Characteristics At Different Growing Period Of Two Winter Wheat Cultivars

With the increase of population, food shortages have become an important problem in Chinese society recent years. The Dongnongdongmai1is the only winter wheat cultivar which could pass the winter securely in Heilongjiang province by now. However, the research of Dongnongdongmai is not explored much.The research started relatively late, and most researches are mainly about on cold tolerance of overwintering stage, so the changes of photosynthetic physiological before overwintering period, the growth and metabolism after returning green stages is insufficient. In this study, cold resistant variety Dongnongdongmai1and Jimai22(from Shan-dong province, as control) were used as experimental materials. Photosynthetic parameters, chlorophyll content, soluble sugar content, sucrose content and starch content of tillering nodes and leaves of Dongnongdongmai1were determined under different growing period of two cultivars in order to study the effects of photosynthetic and physiological characteristics on kernel formation and growth of Dongnongdongmai1.The main experimental results were as follows.(1) Changes of physiological and biochemical before overwintering period.Before overwintering period, the fresh weight, dry weight of two cultivars had an increasing trend while the water content had a smaller decline. With the process of growth soluble sugar content and sucrose content had a trend of decreasing at first, then increasing and reached the minimum during September30th.The starch content in two varieties were low. Chlorophyll content had an increasing trend in two cultivars and Dongnongdongmai1also had a higher content than Jimai22. The photosynthetic rate (Pn) and Transpiration rate (Tr) in two cultivars increased at first and then decreased with the peak reached at October8th and September30th. Before September30th and during October8th to October15th the stomatal factor were the main reason inducing the changes of Pn. Inhibition of Pn was mainly caused by the non-stomatal factor during September30th to October8th.(2) Changes of physiological and biochemical during overwintering periodDuring overwintering period, relative electric conductivity in leaves and tillering nodes of two cultivars had an increasing trend with the temperature decline. With the process of growth, soluble sugar content and sucrose content had an increasing trend at first, then decreasing and reached the maximum during November30th(-10℃),the high content made the Dongnongdongmai1have more tolerance than Jimai22. The starch content in two varieties was low with no significant accumulation under low temperature. Chlorophyll content had an decreasing trend of two cultivars and Dongnongdongmai1also had a higher content than Jimai22.(3) Changes of physiological and biochemical after overwinteringperiodWith the process of growth, photosynthetic rate (Pn) and Transpiration rate (Tr) had an increasing trend at first, then decreasing and reached the maximum during the anthesis. Before anthesis, the stomatal factor was the main reason inducing the changes of Pn. After anthesis, the inhibition of Pn was mainly caused by the non-stomatal factor, chlorophyll content had a trend of increasing at first, then decreasing and reached the maximum during the grain filling stage, while the changing trend of soluble sugar content and sucrose content was "decreasing-increasing-decreasing" and starch content of kernel was increased with the soluble sugar and sucrose content decreased.