硝普钠对黄瓜幼苗缺镁和硝酸盐胁迫的缓解效应

【目的】设施栽培中土壤次生盐渍化严重,导致植株出现缺镁失绿症状。通过研究硝酸盐胁迫下外源NO供体(硝普钠,SNP)对缺镁黄瓜幼苗生长的影响,探究硝酸盐胁迫下外源NO对缺镁黄瓜幼苗的胁迫缓解效应,为解决设施生产中黄瓜幼苗的缺镁失绿症状提供理论指导。【方法】采用水培的方式培养黄瓜幼苗,幼苗长至三叶一心时进行处理。营养液采用山崎配方,镁离子浓度设两个水平为2 mmol/L(正常浓度)和1 mmol/L(缺镁胁迫);硝酸盐浓度设两个水平为14 mmol/L(正常浓度)和140 mmol/L(硝酸盐胁迫);硝酸盐和镁正常浓度为对照。用0.1mmol/L SNP分别缓解缺镁胁迫、硝酸盐胁迫以及缺镁和硝酸盐双重胁迫,用0.1 mmol/L SF(铁氰化钠)处理,观察SNP反应产物的影响;NO-3由Ca(NO3)2·4H2O和KNO3提供,各占1/2,p H由H2SO4调节,保持在5.5 6.5。【结果】1)缺镁胁迫下,黄瓜幼苗株高和叶面积增加值、干物质增长量较正常处理的黄瓜幼苗显著降低;电解质渗漏率、丙二醛含量和可溶性蛋白含量较正常处理的黄瓜幼苗显著升高。缺镁处理的黄瓜幼苗根茎叶中镁离子含量、叶片光合色素含量、光合特性指标、叶绿素荧光及抗氧化酶活性与正常处理的黄瓜幼苗相比明显降低。2)硝酸盐胁迫下,黄瓜幼苗株高和叶面积增加值、干物质增长量、黄瓜幼苗根茎叶中镁离子含量、叶片光合色素含量、光合特性指标、叶绿素荧光及抗氧化酶活性较正常处理的黄瓜幼苗显著降低;电解质渗漏率、丙二醛含量和可溶性蛋白含量较正常处理的黄瓜幼苗显著升高。3)缺镁和硝酸盐双重胁迫下,黄瓜幼苗的相关生长指标和抗逆指标较正常处理的黄瓜幼苗降低或增大更为显著。4)缺镁胁迫,硝酸盐胁迫以及缺镁和硝酸盐双重胁迫下,外施0.1 mmol/L SNP处理的黄瓜幼苗,株高和叶面积增加值、干物质增长量、幼苗根茎叶中镁离子含量、叶片光合色素含量、光合特性指标、叶绿素荧光、可溶性蛋白含量及抗氧化酶活性较未添加SNP处理的黄瓜幼苗显著提高,电解质渗漏率和丙二醛含量则明显降低。外施0.1 mmol/L SF则没有表现出明显的作用。【结论】硝酸盐胁迫下缺镁黄瓜幼苗生长受到明显抑制,出现失绿症状,通过添加0.1 mmol/L SNP,黄瓜幼苗的生长抑制得到明显缓解,说明在硝酸盐胁迫下外源NO对缺镁黄瓜幼苗的胁迫有显著缓解作用,增强黄瓜幼苗的耐盐性和对镁的吸收能力。

Effects of sodium nitroprusside on alleviating magnesium deficiency of cucumber seedlings under NO-3 stress

【Objectives】Soils in the protected cultivation show serious secondary salinization, resulting in magnesium deficiency symptoms of plants. To explore effect of exogenous nitric oxide donor on alleviating magnesium deficiency under NO- 3 stress in the experiment, the effect of exogenous nitric oxide donor(sodium nitroprusside, SNP)on growth of cucumber seedlings under magnesium deficiency was studied for providing a theoretical guidance to solving the problem of chlorosis of cucumber seedlings caused by magnesium deficiency. 【Methods】The hydroponic method was used to cultivate cucumber seedlings, and seedlings with three real leaves were treated, and a basic nutrient solution was prepared according to the Yamazaki formula. The concentration of magnesium was designed as two levels, Mg2+ 2 mmol/L and Mg2+ 1 mmol/L, and the concentration of nitrate was designed as two levels, NO-3 14 mmol/L and NO-3 140 mmol/L. 0.1 mmol/L SNP was applied to decrease the stress of magnesium deficiency and NO- 3 stress on cucumber plants, and 0.1 mmol/L SF(sodium ferricyanide) was used to observe influence of the SNP reaction products. The normal concentration of magnesium and nitrate treatment was set as control. NO- 3 was provided by Ca(NO3)2·4H2O and KNO3 (1∶1), and pH was adjusted by H2SO4 to keep at 5.5-6.5. 【Results】1) The plant height, leaf area and dry matter of cucumber seedlings are significantly lower under magnesium deficiency than those in the control, and the electrolyte leakage rate, the content of MDA and soluble protein of cucumber seedling leaves are increased significantly compared with the control under magnesium deficiency. The magnesium contents of roots, stems and leaves, the Pn, Ci, Gs, Tr, Fv/Fm and ΦPSⅡ,and the activities of SOD and POD of cucumber seedling leaves are decreased obviously compared with the control under magnesium deficiency. 2) The plant height, leaf area and dry matter of cucumber seedlings, the magnesium contents of roots, stems and leaves, the Pn, Ci, Gs, Tr, Fv/Fm and ΦPSⅡ,the activities of SOD and POD of cucumber seedling leaves are significantly decreased compared with the control under NO- 3 stress, while the electrolyte leakage rate, the contents of MDA and soluble protein of cucumber seedling leaves are increased significantly. 3) Under the combined stress of magnesium deficiency and NO-3 stress, the changes of plant growth indicators and physiological indexes of plant stress are more obvious. 4) 0.1 mmol/L SNP significantly increases plant height, leaf area and dry matter of cucumber seedlings, the magnesium contents of roots, stems and leaves, the Pn, Ci, Gs, Tr, Fv/Fm and ΦPSⅡ,soluble protein content, and the activities of SOD and POD of cucumber seedlings under the magnesium deficiency, NO-3 stress or their combined stress. On the contrary, 0.1 mmol/L SF does not show such effect. 【Conclusions】The growth of cucumber seedlings is significantly inhibited, and chlorosis is observed under the magnesium deficiency and/or NO-3 stress, and adding 0.1 mmol/L SNP could mitigate the inhibition of growth of cucumber seedlings, indicating that exogenous nitric oxide could decrease the injury of cucumber seedlings induced by magnesium deficiency and/or NO-3 stress through increasing salt tolerance of cucumber seedlings and magnesium absorption.