Effects of exogenous nitric oxide on physiological characteristics of seedlings of malus hupehensis rehd. under continuous cropping | 外源NO对连作条件下平邑甜茶幼苗生理特性的影响

Chinese. 目的研究外源NO对连作条件下平邑甜茶幼苗生长、根系构型、土壤环境、叶片保护酶活性和氧化损伤的影响，探讨NO减轻连作障碍的机理，为生产上采取减轻苹果连作障碍措施提供理论依据。方法将0―1 000μmol#8226;L-1不同浓度的硝普钠溶液，浇至栽植平邑甜茶幼苗的营养钵中，定期取样测定植株株高、叶面积、根系体积、根尖数、土壤主要微生物数量、酚类物质含量、SOD、POD、CAT、APX酶活性、MDA含量和 释放速率等生理指标。结果试验范围内以200μmol#8226;L-1 SNP 处理减轻连作障碍的效果最好，该浓度显著提高了平邑甜茶幼苗株高、鲜重、叶绿素含量和叶面积，与对照一相比，分别增加了59.69%、74.25%、45.70%和116.58%；该浓度显著增加了根系平均直径、总体积和根尖数等根系构型指标；提高了SOD、POD、CAT、APX等4种保护酶活性；降低了MDA含量、 释放速率，对根际土壤主要微生物（细菌、真菌和放线菌）数量和酚类物质含量影响不大。结论外源NO 可减轻平邑甜茶幼苗连作障碍现象。外源NO对连作土中主要微生物数量和酚类物质含量有一定影响，但二者不是NO 缓解平邑甜茶幼苗生长胁迫的主要原因，SOD、POD、CAT等酶活性提高与MDA含量、 释放速率的显著下降是NO 缓解平邑甜茶幼苗生长胁迫的重要原因。

English. Objective Effects of exogenous nitric oxide on the growth, root architecture, soil environment, activities of protective enzymes and oxidative damage of seedlings of Malus hupehensis Rehd. under continuous cropping were investigated. The action mechanisms of nitric oxide were explored so as to provide a theoretical basis for alleviating apple continuous cropping. Method Sodium nitropprusside (SNP, an exogenous nitric oxide donor) at concentrations of 0-1 000 μmol#8226;L-1 were added to the containers, the plant height, leaf area, root volume, number of tips, quantity of major microorganism groups, phenolic compounds and the activities of protective enzymes (including SOD, POD, CAT and APX) in leaves, malondialdehyde (MDA) content , and producing rate in leaves were investigated. Result The above results indicated that the best alleviating effect was 200 μmol#8226;L-1 SNP. At this concentration, the plant height, fresh weight, chlorophyll content and leaf area were significantly increased, comparing with contrast one, increased by 59.69%, 74.25%, 45.70%, 116.58%, respectively. The parameters of root architecture, such as average diameter, total root volume and number of tips were significantly increased. The activities of SOD, POD, CAT and APX were higher significantly than untreated seedlings, while malondialdehyde (MDA) content and producing rate were lower significantly than untreated seedlings. Exogenous nitric oxide had little effect on the quantity of major microorganism groups (bacteria, fungi and actinomycete) and phenolic compounds in rhizosphere soil. Conclusion The above results indicated that exogenous nitric oxide had an effective function on the alleviation of continuous cropping obstacle in seedlings of Malus hupehensis Rehd. Exogenous nitric oxide had some influence on the biological factors and abiotic factors, but both of them were not the main reasons for alleviating continuous cropping obstacle in seedlings of Malus hupehensis Rehd. The activities of SOD, POD, CAT were improved obviously, while malondialdehyde (MDA) content and producing rate were decreased significantly, which were two kinds of important reasons.