CaCl_2缓解酸枣幼苗NaCl胁迫的主成分分析

Principal component analysis of the alleviating effects of CaCl_2 on NaCl stress in sour jujube(Ziziphus acidojujuba) seedlings

【目的】筛选出影响CaCl_2缓解酸枣幼苗NaCl胁迫的主要指标。【方法】以酸枣水培幼苗为试验材料,研究了0mmol·L-1NaCl(对照)、NaCl处理、NaCl+CaCl_2处理对酸枣幼苗地上和地下部分自由水/束缚水、细胞膜透性、SOD、POD、CAT、MDA的影响,并采用主成分分析法对CaCl_2缓解NaCl胁迫的生理指标进行筛选。【结果】与对照相比,NaCl胁迫下酸枣幼苗地上和地下部分自由水/束缚水降低,细胞膜透性、SOD、POD、CAT、MDA升高。与NaCl胁迫相比,营养液中加入CaCl_2后,酸枣幼苗地上和地下部分自由水/束缚水、SOD、POD、CAT升高,细胞膜透性、MDA含量降低。【结论】通过主成分分析法得出细胞膜透性、MDA、POD、CAT可作为CaCl_2缓解酸枣幼苗地上部分NaCl胁迫的评价指标;细胞膜透性、MDA、SOD可作为CaCl_2缓解酸枣幼苗地下部分NaCl胁迫的评价指标。

[ Objective ] Calcium plays an important role in the responses of plants to stresses. Some studies have indicated that exogenous CaCl2 can reduce NaCl stress in jujube （Ziziphus acidojujuba） seedlings The objective of this hydroponic experiment was to identify indexes that could beused to evaluate the use of CaCl2 to alleviate NaCl stress in sour jujube seedlings [ Methods ]A hydroponic experiment was conduct- ed with three treatments： （i） no NaCl stress （control）, （ii） NaCl stress, and （iii） NaCl stress plus CaCl2, These treatments were chosen based on the results of our preliminary studies. Free water/bound water ra- tio, cell membrane permeability, superoxide dismutase （SOD） activity, peroxidase （POD） activity, catalase （CAT） activity, and malondialdehyde （MDA） concentration were measured in the shoots and roots of ju- jube seedlings. Principal component analysis was used to select physiological indexes for evaluating the al- leviating effect of CaCl2 on NaCl stress. [ Results ] Compared with the control, NaCl stress significantly re- duced the ratio of free water/bound water in the shoots and roots of jujube seedlings on all sampling dates. In contrast, NaCl stress significantly increased cell membrane permeability. On day 5, the cell membrane permeability of shoots and roots in the NaCl stress treatment was 2.62 and 1.24 times higher than in the control, respectively. The NaCl stress significantly increased MDA concentrations in jujube shoots and roots. On day 5, shoot and root MDA concentrations were 1.81 times and 3.27 times higher than those in the control, respectively. Shoot SOD activities were significantly greater in the NaCl stress treatment than in the control on all sampling dates. In jujube roots, SOD activities were significantly greater in the NaCl stress treatment than in the control on days 1, 2, 3, and 4. However, on day 5, NaCl stress significantly re- duced root SOD activities. On day 3, SOD activities in shoots and roots were 1.53 and 1.43 times higher than those in the control, respectively. The NaCl stress significantly increased POD activities in both the shoots and roots. On day 3, shoot and root POD activities were 1.41 and 2.32 times higher than in the con- trol, respectively. The NaCl stress treatment significantly increased CAT activity in jujube roots on all sampling dates. Shoot CAT activities were significantly greater in the NaCl stress treatment than in the control on days 1, 2, 3, and 4. However, there was no significant difference in shoot CAT activity between the control and NaCl stress treatments on day 5. On day 3, the CAT activities in the shoots and roots were 1.96 and 4.10 times higher than those in the control, respectively. Compared with the NaCl stress treat- ment, the NaCl plus CaCl2 treatment significantly increased the free water/bound water ratio on days 4 and 5. On day 5, the ratio in the shoots and roots was 2.54 and 1.04 times higher than those in the NaCl stress treatment, respectively. NaCl stress plus CaCl2 treatment significantly increased shoot SOD activities on days 1, 3, 4 and 5 and root SOD activities on days 1, 2 and 5. On day 5, shoot and root SOD activities were 15.15% and 27.91% higher than those in NaCl stress treatment, respectively. Addition of CaCl2 signifi- cantly increased shoot POD activities on all sampling dates and root POD activities on days 1, 2, 4, and 5. On day 5, shoot and root POD activities were 5.91% and 46.25% higher than those in NaCl stress treatment , respectively. The NaCl plus CaCI2 treatment also significantly increased shoot CAT activities on days 1 to 4 and root activities on days 3 and 4. On day 3, shoot and root CAT activities were 80.63% and 68.53% higher, respectively. The NaCl plus CaCl2 treatment significantly reduced cell membrane permea- bility in shoots on days 3, 4, and 5 and in roots on days 4 and 5. On day 5, cell membrane permeability in roots and shoots were 26.62% and 16.62% lower than that in NaCl stress treatment, respectively. The Na- Cl plus CaCl2 treatment also significantly reduced MDA concentrations in the shoots and roots on all sampiing dates. On day 5, the MDA concentrations in shoots and roots were reduced by 55.22% and 55.00% respectively by addition of CaCl2. [ Conclusion] Principal component analysis indicated that cell membrane permeability, MDA concentration, POD activity, and CAT activity can be used to evaluate the alleviating effect of CaCl2 on NaCl stress in sour jujube shoots. In sour jujube roots, cell membrane permeability, MDA concentration, and SOD activity are good indicators.