【作者】 李凯；

【导师】 张满让；

【作者基本信息】 西北农林科技大学 ， 果树学， 2022， 硕士

【摘要】 土壤盐渍化是我国北方干旱和半干旱地区苹果生产的主要限制因素之一,深入研究盐胁迫条件下苹果的响应机制,对提高苹果的抗盐性以及培育抗盐性较强的苹果品种具有重大意义。本研究以苹果砧木M26组培苗为试验材料,120 mmol·L^-1NaCl模拟钠盐胁迫,通过喷施5种浓度NO供体硝普钠（SNP）:50μmol·L^-1,100μmol·L^-1,150μmol·L^-1,200μmol·L^-1和300μmol·L^-1,系统地研究了外源NO对NaCl胁迫下M26苹果幼苗生长发育、养分吸收、蔗糖代谢、氮代谢以及抗氧化系统的影响,为提高苹果的耐盐性提供理论依据,主要研究结果如下:1.NaCl胁迫显著抑制了M26苹果幼苗的生长、光合作用和养分吸收能力,适宜浓度SNP的喷施处理改善了NaCl胁迫对幼苗株高、干鲜重、叶绿素含量、光合作用和叶绿素荧光系统的抑制,增强了幼苗对氮、磷和钾的吸收能力,并以200μmol·L^-1SNP处理的缓解效果最佳。2.NaCl处理后,M26苹果幼苗蔗糖磷酸合成酶（SPS）和蔗糖合成酶（SS）的活性升高,酸性转化酶（AI）和中性转化酶（NI）的活性降低,Md SPS6、Md Su Sy2、Md SUT1的表达上调和Md NINV2的表达下调,适宜浓度SNP的喷施处理进一步提高了SPS和SS的活性以及Md SPS6和Md Su Sy2的表达水平,并且AI和NI的活性也得到了提高,说明外源NO能够提高NaCl胁迫下M26苹果幼苗的蔗糖代谢水平,进而增强植株在NaCl胁迫下的耐受性。3.NaCl处理后,M26苹果幼苗铵态氮的含量升高,表现出了铵的毒害作用,并且幼苗硝态氮的含量以及硝酸还原酶（NR）、谷氨酰胺合成酶（GS）和谷氨酸脱氢酶（GDH）的活性均降低,同时Md NR和Md NIR的表达下调,幼苗的氮同化能力受到抑制,适宜浓度SNP的喷施处理不仅提高了NR、GS、GDH的活性和硝态氮的含量,降低了铵态氮的含量,而且也上调了Md NR和Md NIR的表达,说明外源NO能够提高NaCl胁迫下M26苹果幼苗的氮代谢能力。4.NaCl处理后,M26苹果幼苗的叶片相对电导率以及过氧化氢（H₂O₂）和丙二醛（MDA）的含量增加,超氧化物歧化酶（SOD）、过氧化物酶（POD）和抗坏血酸过氧化物酶（APX）的活性降低,同时幼苗自身也通过提高脯氨酸（Pro）和可溶性蛋白的含量以及上调Md NHX1和Md AKT1的表达来抵御NaCl胁迫导致的渗透胁迫和离子毒害;适宜浓度SNP的喷施处理降低了幼苗叶片的相对电导率以及H₂O₂和MDA的含量,提高了SOD、POD、CAT和APX的活性,并进一步增加了Pro和可溶性蛋白的含量,表明NaCl胁迫下外源NO能够增强M26幼苗的抗氧化能力和渗透调节能力,进而提高植株的耐盐性。综上所述,外源NO能够改善NaCl胁迫下M26苹果幼苗的光合作用和抗氧化能力,提高幼苗的蔗糖代谢和氮代谢水平,并增强幼苗对矿质元素的吸收能力,缓解了NaCl胁迫对幼苗的伤害,进而促进植株的生长发育。更多还原

【Abstract】 Soil salinization is one of the major limiting factors for apple production in arid and semi-arid regions of northern China.An in-depth study on the response mechanism of apples under salt stress conditions is of great significance to improve the salt resistance of apples as well as to breed apple varieties with stronger salt resistance.In this study,the effects of exogenous NO on the growth and development,nutrient uptake,sucrose metabolism,nitrogen metabolism and antioxidant system of M26 apple seedlings under NaCl stress were systematically investigated by spraying five concentrations of NO donor sodium nitroprusside（SNP）:50μmol·L^-1,100μmol·L^-1,150μmol·L^-1,200μmol·L^-1,300μmol·L^-1,using apple rootstock M26 histoculture seedlings as test materials and 120mmol·L^-1NaCl to provide a theoretical basis for improving the salt tolerance of apples.The research results are as follows:1.NaCl stress significantly inhibited the growth,photosynthesis and nutrient uptake capacity of M26 apple seedlings,and the spray treatment with appropriate concentration of exogenous SNP improved the inhibition of NaCl stress on seedling height,dry and fresh weight,chlorophyll content,photosynthesis and chlorophyll fluorescence system,and enhanced the uptake capacity of nitrogen,phosphorus and potassium of seedlings,and the best alleviation effect was achieved by 200μmol·L^-1SNP treatment.2.NaCl stress increased the activities of sucrose phosphate synthase（SPS）and sucrose synthase（SS）and decreased the activities of acidic convertase（AI）and neutral convertase（NI）in M26 apple seedlings,and up-regulated the expression of Md SPS6,Md Su Sy2,Md SUT1 and down-regulated the expression of Md NINV2.The spray treatment with suitable concentration of SNP further increased the activity of SPS and SS as well as the expression levels of Md SPS6 and Md Su Sy2,and the activities of AI and NI were also increased,indicating that exogenous NO can increase the sucrose metabolism level of M26apple seedlings under NaCl stress,and thus enhance the tolerance of the plants to NaCl stress.3.NaCl treatment increased the ammonium nitrogen content of M26 apple seedlings,which exhibited the toxic effect of ammonium,and decreased the nitrate nitrogen content of seedlings and the activities of nitrate reductase（NR）,glutamine synthetase（GS）,and glutamate dehydrogenase（GDH）,and also down-regulated the expression of Md NR and Md NIR,so that the nitrogen assimilation ability of seedlings was inhibited.The spraying treatment with suitable concentration of SNP not only increased the activities of NR,GS,GDH and nitrate nitrogen and decreased the content of ammonium nitrogen,but also up-regulated the expression of Md NR and Md NIR,indicating that exogenous NO could improve the nitrogen metabolism of M26 apple seedlings under NaCl stress.4.NaCl stress increased the relative leaf conductivity and the content of hydrogen peroxide（H₂O₂）and malondialdehyde（MDA）,and decreased the activities of superoxide dismutase（SOD）,peroxidase（POD）,and ascorbate peroxidase（APX）in M26 apple seedlings.The seedlings themselves resisted the osmotic stress and ion toxicity caused by NaCl stress by increasing the content of proline（Pro）and soluble protein and by upregulating the expression of Md NHX1 and Md AKT1 to resist osmotic stress and ion toxicity caused by NaCl stress.Spraying a certain concentration of SNP reduced the relative conductivity and the content of H₂O₂and MDA in seedling leaves,increased the activities of SOD,POD,CAT and APX,and further increased the content of Pro and soluble protein.It was shown that exogenous NO treatment under NaCl stress could enhance the antioxidant capacity and osmoregulatory capacity of M26 apple seedlings,and thus improve the salt tolerance of the plants.In conclusion,exogenous NO could improve photosynthesis and antioxidant capacity of M26 apple seedlings under NaCl stress,enhance sucrose metabolism and nitrogen metabolism levels of seedlings,and enhance nutrient uptake and utilization of seedlings,alleviating the damage caused by NaCl stress to seedlings,thus promoting plant growth and development.更多还原