Studies On Mechanism Of Fruit Cracking And Bibulous Dynamics In Zizyphus Jujba Mill

Zizyphus jujuba Mill.is one of the most national representative fruit trees in China. It not only has very high economic benefit but also has very important ecological benefits. Problems of fruit cracking caused by rain in the period of mature have brought a great economic losses, which have a serious influence to the sustainable development of China’s jujube industries. In this study, inorder to solve the problem of fruit cracking, we have found some of unti-fruit cracking germplas by investigating the nature fruit cracking condition in the places of Northwest a&f university jujube experiment stations, shanxi fruit research institute national germplasm resources nursery of jujube, the world jujube exposition garden in LingWu Ningxia province and state forestry jujube seed breeding station in Cangzhou Hebei province. According to the studies of fruit anatomy structure and water absorbent kinetics between the different varieties of jujube, we futher improved the jujube fruit cracking mechanism. The main results are as follws:According to the previous record, visiting jujube farmers and field adjustable sampling,4extremely anti-crack variety have been celected, wich are Xiangzao、Shenglizao、 Xiangfenmuzao and Muzao No5. Muzao No5is found for the frist time, preliminary find that the fruit has very good quality, high yield, the crack resistance and disease resistance are very strong, especially the resistance to crack, far stronger than common jujube, even reached the level of the resistance of Xiangzao, wich provide new materials to jujube breeding.Jujube fruit of easily crack variety, medium crack variety and extremely anti-crack variety that all during maturation stage were studied on the thickness of epidermal cells, cavity size under stalk, pulp cavity size, pulp cell size and there changes by useing indoor fruit soak method, paraffin method and microscopic measurement technology.The results show that the thickness of epidermal cells have extremely significant difference between3different cracking levels of jujube varieties. Extremely anti-crack variety have the thickest skin while easily crack variety have the thinnest one, the thicker the skin, the more difficult cracking. The ratios of cavity under stalk occupied jujube fruit are extremely different, between3different cracking levels of jujube varieties. Extremely anti-crack variety have the minimum ratio which is0.24%～0.26%, on the contrary, easily crack variety have the maximun ratio which is about0.62%. The smaller the cavity size under stalk, the more difficult cracking.The pulp cavity sizes are extremely different between3different cracking levels. Extremely anti-crack variety is the very smallset(3380.82～3879.12μm2)while easily crack variety is the biggest(9300.4942～10809.86μm2),the smaller the pulp cavity, the more difficult cracking. Fruit crack and pulp cell size have no significant correlation, which closely related to the bibulous rate, the faster the pulp cell sop up water, the easier the fruit crack. In a summary, thickness of epidermal cells,cavity size under stalk, pulp cavity size and the bibulous rate of pulp cells together determine the Jujube fruit crack.Absorbent kinetics equation of different varieties were established.In the four absorption kinetics fitting models, Logistic model is the best to fit the experimental data, and have the minimum error. Because the square of the correlation coefficient (R2) in Logistic model is maximum, and the residual sum of squares (SSE) is minimum. Different jujube varieties have different absorption kinetics equation form, reflecting the different fruit water absorption nature of the different varieties. The absorption kinetics equation of extremely easily crack variety is:y=16.4419/1+46.2914×x-1.4074,easily crack variety is y=14.7276/1+129.5596×x-1medium crack variety is y=13.2556/1+1524.2617×x-1.9113,anti-crack variety is y=9.3660/1+1485.3085×x-1.8096, extremely anti-crack variety is y=7.0952/1+637.2572×x-1.5341.Through the above research, not only provide valuable material for jujube crack resistance breeding, but also improve the anti-cracking mechanism of jujube further, explained the water absorption characteristics of different jujube varieties and its influence factors, wich provide important theoretical basis for cracking resistance breeding, scientific irrigation and timely harvest in the jujube production process.