Abstract:

A pot experiment was conducted to study effects of aged peach orchard soil on the growth of Malus hupehensis Rehd. seedlings，and M. hupehensis Rehd. was used in this study. The biomass，root structure parameters，root respiration rate，root protection，photosynthetic parameters of M. hupehensis Rehd. and microbial population in soil were measured. Three treatments were designed as follows：fallow soil（the soil beside peach orchard），methyl bromide fumigation aged peach orchard soil and aged peach orchard soil. The results showed that the plant height，plant ground diameter，fresh weight and dry weight of M. hupehensis Rehd. in aged peach orchard soil were significantly lower than those of the fallow soil and methyl bromide fumigation aged peach orchard soil，and 17.59%，13.51%，23.22% and 28.61% were lower than those of the fallow soil；and 20.54%，17.29%，33.28% and 39.21% were less than those of methyl bromide fumigation aged peach orchard soil. The root length，root surface area and root volume were decreased by 37.57%，36.33% and 46.63% respectively compared with fallow soil，and 43.62%，48.67% and 54.11% were lower than those of methyl bromide fumigation aged peach orchard soil. The root respiration rate，superoxide dismutase（SOD），peroxidase（POD）and catalase（CAT）activities were significantly decreased by 28.21%，43.91%，44.46%，51.44% respectively compared with fallow soil，and 36.88%，57.78%，54.88% and 57.59% were lower than those of methyl bromide fumigation aged peach orchard soil respectively. The net photosynthetic rate（Pn）were decreased by 40.8% and 49.65% respectively compared with fallow soil and methyl bromide fumigation aged peach orchard soil. The fungi number of aged peach orchard soil was 1.91 times higher than that of fallow soil，while the bacteria number was 47.80% lower than that of fallow soil. The ratio of bacteria to fungi was：fallow soil > methyl bromide fumigation aged peach orchard soil > aged peach orchard soil. Therefore，M. hupehensis Rehd. seedlings directly planted in aged peach orchard soil was not good for its growth. But after methyl bromide fumigation，the damage effect was obviously reduced.

Key words: Malus hupehensis, aged peach orchard soil, photosynthetic rate, microorganism, protective enzyme system activity