Effects Of Exogenous Nitric Oxide On Seedlings Of Malus Hupehensis Rehd. Under Continuous Cropping

This study was performed in the fruit roots laboratory of college of horticultural science and engineering, shandong agricultural university and state key laboratory of crop biology from 2009 to 2011. In this study, a commonly apple rootstock M. hupehensis seedlings were used as materials. Effects of exogenous nitric oxide on the biomass, root architecture, activities of protective enzymes, oxidative damage and soil environment of seedlings of Malus hupehensis Rehd. under continuous cropping were investigated. The main results were as follows:1. Comparing with clear water treatment, the plant height, fresh weight, chlorophyll content and leaves area were significant increased in continuous cropping soil with. SNP treatment. The growth of seedlings had some differences in different concentrations of SNP under continuous cropping. At 200μmol·L-1 concentration, the plant height, fresh weight, chlorophyll content and leaves area were significantly increased, comparing with clear water treatment, increased 59.69%, 74.25%, 45.70% and 116.58% respectively; with the SNP concentration increasing, plant height, fresh weight, chlorophyll content and leaves area were decreased.2. Comparing with SNP treatment, the total root volume were significant decreased in continuous cropping soil with clear water. The average diameter, total root volume, total root surface and number of tips had some differences in different concentrations of SNP under continuous cropping. At 200μmol·L-1 concentration, the average diameter, total root volume, total root surface and number of tips were the highest, with the SNP concentration increasing, root average diameter, total volume, total root surface area and number of tips were significantly decreased. Comparing with SNP 200μmol·L-1 treatment, the total volume and total root surface area decreased 59.1% and 64.7% than SNP 1000μmol·L-1 treatment.3. Comparing with SNP treatments, the number of bacteria, fungi and actinomyces had not significantly differences, SNP treatment reduced the density of herbivorous nematodes and soil pH, but different concentrations of SNP treatment herbivorous nematode density and soil pH had some differences, with the SNP concentration increasing, the density of nematode herbivores became smaller. Gallic acid, phloretin, p-hydroxybenzoic acid, ferulic acid and caffeic acid had some differences during with different concentrations of SNP treatment, but total phenolic acids.had not significant differences.4. The activities of SOD, POD, CAT and APX were affected by different concentrations of SNP treatment. Different concentrations of SNP treatment showed that, exogenous NO had dose effect with SOD, POD, CAT and APX, That was low concentrations increased enzyme activity, but tall concentrations decreased enzyme activity.