Effects Of NaCl Stress On Ion Absorption,Distribution And The Expression Of MicroRNA In Sour Jujube Seedlings

A hydroponic experiment was conducted to study the effects of Na Cl concentration（ 0, 50, 100, 150 and 200 mmol·L-1） on reactive oxygen species, cell membrane permeability, root activity, and the concentrations of Na⁺, K⁺,Ca²⁺, and Mg²⁺ in different organs of sour jujube seedlings（Ziziphus acidojujuba C. Y. Cheng et M. J.Liu）. This experiment also constructed five small molecule RNA libraries（CK, 6 h,12 h, 24 h and 48 h under 150 mmol·L-1 Na Cl treatment）.We compared the sequences, length, the first base preference of different samples, identified the known mi RNAs and predicted the new mi RNAs and their target genes in order to provide materials for revealing the salt tolerant mechanism of sour jujube. In addition, We also Effects of 10 mmol·L-1CaCl₂ on ion absorption and distribution in sour jujube seedlings under 150 mmol·L-1Na Cl stress.In addition, We also studied the effects of exogenous 10 mmol·L-1CaCl₂ on superoxide（O2.-） production rate, hydrogen peroxide（H2O2） concentration, cell membrane permeability,malondialdehyde（MDA） content,and K⁺, Ca²⁺, Na⁺, Mg²⁺ concentrations in different organs in sour jujube seedlings under Na Cl stress to explore the theoretical mechanism of calcium in alleviating salt stress, and to provide reference information for further development of jujube industry in saline alkali land. Main research results are as follows:1. Results showed no leaf wilting after six days in 0, 50 or 100 mmol·L-1 Na Cl treatments, 54% leaf wilting was observed in the 150 mmol·L-1 Na Cl treatment, 73% leaf wilting was observed in the 200mmol·L-1 Na Cl treatment. As Na Cl concentration increased, the cell membrane permeability of root, stem,leaf increased, while root activity of sour jujube seddlings decreased. The jujube leaves presented brown patches in the 150, 200 mmol·L-1 Na Cl treatments by using 3,3 N-Diaminobenzidine Tertrahydrochlorid（DAB） staining and blue spots in the 50, 100, 150, 200 mmol·L-1 Na Cl treatments by using（Nitrotetrazolium Blue Chloride） NBT staining. Na⁺ and Cl- concentrations in roots, stems, and leaves were positively correlated with the treated Na Cl concentrations. K⁺, Ca²⁺, Mg²⁺ concentrations in leaves were negatively correlated with the treated Na Cl concentrations. The Na Cl treatments had no significant effect on K⁺ and Mg²⁺ concentrations in roots and stems. The 200 mmol·L-1 Na Cl treatment significantly reduced Ca²⁺ concentrations in roots and stems. Though the Na Cl treatments significantly reduced the K⁺/Na⁺, Ca²⁺/Na⁺, and Mg²⁺/Na⁺ ratios of roots, stems and leaves, the K⁺/Na⁺ ratio of roots was always greater than 1, which may be an adaptation of sour jujube seedlings to salt stress.2. Through the study of 10 mmol·L-1 CaCl₂ on O2.-production rate, H2O2 concentration, cell membrane permeability, MDA content, and the Na⁺, K⁺, Ca²⁺, Mg²⁺ concentrations in different organs of sour jujube seedlings under 150 mmol·L-1 Na Cl stress, we found 53% leaf wilting after six days in the 150 mmol·L-1Na Cl treatment.The Na Cl treatment significantly increased leaf O2.-production rates, H2O2 concentrations,cell membrane permeability, MDA concentrations and Na⁺ concentrations in roots, stems, and leaves. The Na Cl treatment significantly decreased K⁺, Ca²⁺ and Mg²⁺ concentrations in roots. Compared with the Na Cl treatment, 29% of the leaves showed wilting symptoms after adding exogenous CaCl₂. The Na⁺Ca treatment significantly decreased leaf O2.-production rates, H₂O₂ concentrations, cell membranepermeability, MDA concentrations and Na⁺ concentrations in roots, stems and leaves. K⁺ concentrations and K⁺/Na⁺ ratio in roots were significantly increased in the Na⁺Ca treatment. Ca²⁺ concentrations in stems,leaves and Mg²⁺ concentrations in roots were also increased. Thus exogenous CaCl₂ reduces Na Cl stress in sour jujube by reducing Na⁺ concentrations and increasing K⁺, Ca²⁺ and Mg²⁺ concentrations in various plant organs.3. By using small RNA sequencing, 11,808,185 and 11,260,090 and 12,275,617 and 12,200,968 and11,420,737 reads were respectively obtained in the five constructed small RNA libraries. 118, 96, 98, 97 and 98 known mi RNAs were identified in the five small RNA libraries through blast analysis in the mi RBase database. 545, 258, 311, 350, 188 new mi RNA precursors and 355, 164, 200, 220, 125 mature sequences were predicted. The target genes of mi RNA were also predicted.