Physiological Mechanism Of Dongzao Fruit Drop And Effect Of Girdling Width To Dongzao Development And Quality

Ziziphus jujuba cv. Dongzao has been widely taken as the best jujuba fresh-fruit cultivar at present. Dongzao was a superior cultivar which has a cultivation history of more than one hundred years, but the research of it just was began recently, planting techniques were not so perfect, and there were many technical questions in its production, such as the lower natural setting percentage. In this experiment, the physiological mechanism of Dongzao fruit drop was studied. And for increasing natural setting percentage availably and improving fruit quality, the variation of soluble sugar, titratable acid, vitamin C and soluble protein were also observed during fruit development with girdling Dongzao tree. The main results were as follows:1 Different tree vigor affected the degree of dropping fruits. The number of dropping fruits was strong tree > feeble tree > middle tree. There were two peaks of dropping fruit during the fruit development, the first one took place in the last ten-day of July; the second one in the last ten-day of September. The degree was severer in the former period than in the later.2 Most Dongzao embryo grew before stone hardening stage. Seed abortion was one of heredity character, and it was no relation with tree vigor.3 The phenomenon of dropping fruit occurred for seed abortion, IAA> GA^ ZR of low content and ABA of high content. There were also many reasons in the dropping fruits, such as N of the high content, and Ca, soluble sugar and protein of the low content, etc.4 Different girdling widths did not affect the growth tendency of Dongzao fruit. The growth curves of fresh weight, volume, diameter and length showed double "s" shape, but they were not modeled.5 The soluble sugar contents in different girdling width Dongzao tree had the same trend, i.e., in the early stage of fruit development, the changes of the contents of soluble sugar were not obvious; during fruit maturation the contents of soluble sugar accumulated rapidly. Before maturation the content of sucrose was little, but the content was run up with fruit developing, and it became the important soluble sugar at maturation. The highest content of soluble sugar was the fruit of tree with girdling 1.2cm, and the lowest was one with girdling 0.6cm.6 The contents of titratable acid in different girdling width Dongzao tree had the same trend. The contents were the highest in the early stage of fruit development. And they decreased with the development of fruits.7 The contents of vitamin C in different girdling width Dongzao tree showed low→high→low in the course of fruit development and kept a high level in the middle ten-day of August.8 The contents of soluble protein in different girdling width Dongzao tree had the same trend. The highest level was in the first ten-day of July and the middle ten-day of September.9 The different girdling width affected growth of tree. The natural setting percentage of girdling width 0.9cm was highest in the trees with girdling. The contents of soluble sugar and soluble protein were highest in the fruit of tree with girdling 1.2cm. And considering the quality and yield, girdling width between 0.9cm and 1.2cm was suit to 4 years Dongzao tree in full bloom.