Cold resistance physiology of Cercidiphyllum japonicum under chilling stress

Abstract:
In this study, we explored the cold resistance physiology of Cercidiphyllum japonicum (C. japonicum) under chilling stress. Eight-year-old seedlings of C. japonicum introduced in Beijing were used as experimental materials, and their one-year dormant branches were selected and treated under -5, -10deg C, -15deg C, -20deg C, -25deg C and -30deg C, respectively. The relative electrical conductivity, contents of malondialdehyde (MDA), soluble sugar, the activity of peroxidase (POD), contents of total water, and rate of bound water content to free water content were measured; and the semi lethal temperature (LT50) was calculated by fitting relative electrical conductivity in combination with the logistic equation. These results indicated a strong cold resistance of C. japonicum, with LT50 as -20.92deg C. With the decrease of the treatment temperature, the relative electrical conductivity gradually increased; MDA and soluble sugar, the activity of POD, and the ratio of bound water content to free water content tended initially rose and then declined at a lower temperature, while the contents of total water showed an opposite trend. There was some correlation among the indexes, and the principal component analysis showed that the accumulative contribution rate of six physiological indexes reached 90.996%. The activity of POD, soluble sugar, and rate of bound water content to free water content were the most important physiological indexes characterizing the cold resistance of the plant. In summary, with tolerance to a low temperature < -20deg C, C. japonicum could adapt to the Beijing winters characterized by low temperatures, as well as to cities with similar latitude, which encourages the introduction and cultivation.