Effects Of Low Temperatures On The Seedling Of Zizyphus Mauritiana Lam And Fruit Quality

Abstract: Zizyphus mauritiana is a tropical fruit, and has been widely planted in Southern China in recent years, and the low temperature can often cause serious damages to it according to previous reports. In order to establish the low temperature injury grades on Z. mauritiana, one year Z. mauritiana graft seedling(Cuimi) were treated in the lowest temperature(Tmin) 2°C, 1°C, 0°C,-1°C,-2°C,-3°C and-4°C, the diurnal temperature differences were 15°C, in climate chamber for 1d, 2d and 3d, three repetitions. Then observed the morphological and physiological and biochemical indexes of Z. mauritiana after daily treatment, and watching the recovery situation under the condition of 10 d in normal temperature, and analysing the lowest temperature of damage on the leaves and branches of Z. mauritiana, thus setting up the chilling injury index of Z.mauritiana seedlings preliminarily. Meantime, do geographical displacement test under 3different altitude in Nanling Nature Reserve of Guangdong Yangshan County during the Winter of 2014-2015 or 2015-2016 to test and revise the index, and collecting ripe fruits from different time of Fengshun's orchard and Chaozhou's orchard for determining its physical and nutritional quality, and then analysing the relationship between meteorological factors and quality of Z. mauritiana. The results of the study are as follows:(1)SOD activity with decrease of daily minimum temperature, showed an upward trend; relative conductivity with temperature to reduce or prolong the processing time have varying degrees of increase; with daily maximum temperature decreased, MDA content increased gradually, but when the temperature dropped to –2°C can significantly observed, with the extension of the processing cycle, MDA content is decreased; thecontent of soluble sugar and soluble protein content with daily minimum temperature is reduced, showed a trend of first increased and then decreased, and free proline content with daily minimum temperature decreasing rising trend.(2)The results of manual control test were consistent to geographical displacement test. The low temperature injury index were divided into 5 grades, that were, death,Tmin?-4°C,and the processing time is more than 1 day; serious injury,-4°C<Tmin?-3°C,and the processing time is more than 3 day; moderate injury,-3°C<Tmin?-2°C. and the processing time is more than 1 day; light injury, Tmin=-2°C,and the processing time is more than 3 day;-2°C is the critical temperature of jujube plant frostbite.(3)The Volume, fresh weight, and solid content of Zizyphus mauritiana have a significant correlation with average temperature, minimum temperature and daily range of temperature; Besides there is a certain correlation between fruit firmness and air relative humidity; The contents of soluble sugar have a good positive correlation with daily range of temperature and photosynthetic active radiation; The correlation between VC content and meteorological factors was not significant.