Comparative Studies On The Fruit Cracking Between The "Jinsi" And "Tiaoyuan" Jujube

"Jinsi" and "Tiaoyuan" jujube are the deciduous leaf small trees of Ziziphus zizyphus as well as the two main fresh jujube in the hilly areas of Deyang city currently. Among them, "Tiaoyuan" jujube is a local variety while "Jinsi" jujube is a new variety introduced and cultivated in recent years. And their cracking rates are respectively around 15% and about 40% which shows that the two jujue have significant difference in the cracking rate. So they are selected as the test materials of the research. Meanwhile, according to the direction of the macro to micro, their cracking phenomenon and occurrence, splitting resistance, tissues, ultrastructure and physiologic and biochemical index are compared deeply. So that it can reaveal cracking mechanism of jujube and provide theoretical and practical basis for the control of fruit cracking and then expanding the planting area of jujube in Sichuan hilly area.The main results are as follows:(1) The cracking rate of "Jinsi" jujube varies greatly from 2011 to 2013 while "Tiaoyuan" jujube’s is relatively stable. The main period of their cracking is respectively in September and August each year. During this period, the cracking of "Jinsi" jujube is impacted greatly by precipitation and relative humidity and less affected by temperature, while "Tiaoyuan" jujube’s has little impact on the three meteorological elements.(2) The cracking index of "Jinsi" jujube is 0.23 belonging to the fissile species and the cracking index of "Tiaoyuan" jujube is 0.01 belonging to the crack varieties.(3) Observed on the peel anatomical structure of "Jinsi" and "Tiaoyuan" jujube, the outcome shows that the keratinocytes is thinner, the pulp cells arrange more closely, and the cavity is smaller and less, the more cracking. And observed in the ultra-microscope, there distributes many sunken directly stomatas on the peduncle wa site of "Tiaoyuan" jujube. And this type of stomata can maintain the water balancethus reducing fruit cracking. But the type and the number of "Jinsi" jujube’s stomata is concavoconvex and relatively small. Simultaneously its function remains to be further studied.(4) Concerning the parameters of jujube’s physiological and biochemical, the reducing sugar content of "Jinsi" jujube, a kind of easily dehiscent fruit variety, is 8.5% significantly higher than the cracking variety "Tiaoyuan" jujube(7.2%), which indicates that reducing sugar content may be positively related with cracking. In addition, in the normal and cracking fruit of the same species, the content of sucrose and water may also positively correlate with cracking. Meanwhile, in the normal and cracking fruit, the Mg content of "Jinsi" cracking jujube (0.08% and 0.07%) is significant than normal jujube’s(0.07% and 0.05%). So it can be inferred that the peel’s higher levels of Mg has an impact on cracking to some extent.In summary, the fruit cracking of jujube is commonly influenced by a variety of factors, which belongs to a complex physiological disease. In this study, the internal structure including the thickness and morphology of keratinocytes, the type and the number of stomata, the pulp cell arrangement and the cavity size and number, has obviously difference between "Jinsi" and "Tiaoyuan" jujube. As a result, the jujube’s ability to resist adverse external environment is different. But the decisive role on the structure is mainly genetic varieties. And this can be inferred that the relationship between genetic factors and cracking is very close, while it remains to be further studied with the mineral elements, sugar and water content.