The Alleviation Effect Of CaCl₂on NaCl Stress In Ziziphus Jujuba Hu

With Ziziphus jujuba Hu as test material, the influence on the germination rate of Sour Jujube seedsand the growth of root system from different concentrations of NaCl, was investigated. Moreover, theinfluence on the germination rate of Sour Jujube seeds and the growth of root system from differentexogenous substances (GSH, Spd, KNO3, CaCl2), based on NaCl stress, was also studied. Sour Jujubeseedlings cultivated under hydroponic system was used as research object, Our research aimed toexplore effect of CaCl2on seed morphological indexes、oxidative damage、electrical conductivity、geneexpression and roots structure of salinity-stressed Sour Jujube. We sought to set the basis for betterunderstanding the mechanism of jujube in response to salt stress. Main result are as followings:1、Our data showed that: compared with control, NaCl can inhibit the germination rate of Sour Jujubeseeds and the growth of lateral roots when its concentration is higher than60mmol/L. As far as fourdifferent exogenous substances were concerned, they all could significantly promote the germination rate ofSour Jujube seeds, GSH, Spd and CaCl2could promote the growth of root system, among which GSH andCaCl2could promote the development of lateral roots. CaCl2was selected as alleviation substances in thenext experiment.2、The Sour jujube leaf and root of were used as materials for studying the effect of10mmo/L CaCl2on cell membrane permeability、malondialdehyde（MDA）contents、superoxide dismutase（SOD）、peroxidase（POD）and catalase（CAT）activities under NaCl stress。The results show that the cellmembrane permeability and content of MDA was increased, the activities of SOD, CAT and POD increasedfirstly and then decreased in leaf but continued to rise in root with stress time: after adding CaCl2(10mmo/L), the cell membrane permeability and MDA content decreased while SOD, POD and CAT activitiesincreased compared with that of no CaCl2addition. The results indicated that CaCl2could raise theactivities of antioxidant enzymes and decrease the membrane lipid peroxidation for Sour jujube seedlings,which could alleviate the damage of NaCl stress and improve the NaCl stress adaptability of Sour jujubeseedlings.3、Sour Jujube Seedlings were treated by10mmo/L CaCl2under NaCl stress, qRT-PCR method wasused to study the relative expression of antioxidase genes of sour jujube. The results showed that relativeexpression of POD mRNA and CAT mRNA of sour jujube increased with the enlargement of NaClconcentration and the extension of process-time, however, the relative expression of GPX mRNA and APXmRNA increased at first, but then reduced with the extension of process-time. The relative expression ofPOD mRNA. CAT mRNA and APX mRNA of sour jujube with CaCl2treatment was always higer thanthese without CaCl2, however, the relative expression of GPX mRNA reduced latterly, the higher relativeexpression of POD and CAT mRNA of leaves with CaCl2treatment resulted in the higher activities ofPOD and CAT. 4、Sour jujube seedlings were treated by10mol/L CaCl2under NaCl stress, the structure of Sourjujube roots was studied by paraffin sectioning and immunohistochemistry. The result showed that a partof epithelial cells shrinked and disintegrated to form a big air cavity under NaCl stress. The number ofcatheters in the roots reduced, the Density of catheters lowered and the diameter of catheters reduced withenlargement of NaCl concentration, at the time,the arrangement of the vascular bundles changed obviously.CaCl2could prohibit the number of catheters from reducing under NaCl stress, whereas the diameter ofcatheters was smaller and the lignification degree of roots strengthened.