The Effect Of Paecilomyces Variotii By Alleviating Salt Stress On Melon

Melon（Cucumis melo L.）is an annual vine herb.With the increasing demand of consumers for melon quality,the planting area is also increasing.In recent years,the cultivation area of protected melon in China has expanded rapidly,and the problem of soil salinization has become increasingly prominent,which has become one of the important abiotic stresses restricting melon production.This experiment was conducted to study the effects of ZNC on seed germination and seedling growth of muskmelon under salt stress,and the physiological mechanism of alleviating salt stress.The results are as follows:1.ZNC can significantly alleviate the inhibition of salt stress on melon seed germination（1）When melon seeds were treated with 0,50,100,150 and 200 mmol·L^-1 Na Cl solution,it was found that Na Cl above 100 mmol·L^-1 significantly inhibited the germination rate,taproot,length,lateral root number and seedling fresh weight of melon seeds;therefore,100mmol·L^-1 Na Cl was selected as the effective stress treatment.After 7 days of germination,it was found that 3～7 ng·mL^-1 ZNC could alleviate salt stress,especially 7 ng·mL^-1 ZNC compared with salt stress treatment,ZNC had the best alleviating effect,which significantly increased seed germination rate（25.42%）,main root length（63.7%）,lateral root number（176.7%）and seedling fresh weight（56.3%）.（2）7 ng·mL^-1 ZNC treatment significantly reduced the inhibition ofα-amylase,β-amylase and total amylase activities in cotyledons under Na Cl stress,and increased the activities of glutamine synthetase（GS）,nitrate reductase（NR）,glutamate synthetase（GOGAT）,superoxide dismutase（SOD）,peroxidase（POD）,catalase（CAT）and ascorbate peroxidase（APX）in radicle,It reduced the production rate of O₂.^-and the content of H₂O₂and MDA,alleviated the oxidative stress induced by salt stress on radicle.2.Root application of ZNC could significantly alleviate the inhibition of salt stress on muskmelon seedling growth（1）The seedlings of muskmelon were treated with 0,50,100,150 and 200 mmol·L^-1Na Cl solution.It was found that the growth of plant height,stem diameter,stem leaf and root system of muskmelon seedlings were significantly inhibited by more than 150 mmol·L^-1 Na Cl solution.Therefore,150 mmol·L^-1 Na Cl was selected as the effective stress treatment.After 7days of salt stress,root irrigation with 0,3,5,7 and 10 ng·mL^-1 ZNC solution could significantly alleviate the inhibition of salt stress on the growth of melon seedlings.（2）5 ng·mL^-1 ZNC had the best alleviating effect,significantly improved the photosynthetic performance,superoxide dismutase（SOD）,peroxidase（POD）,catalase（CAT）,glutamine synthetase（GS）,nitrate reductase（NR）,glutamate dehydrogenase（GDH）and glutamate synthetase（GOGAT）activities of muskmelon seedlings under salt stress.ZNC could reduce the accumulation of MDA,hydrogen peroxide（H₂O₂）and superoxide anion（O₂.^-）induced by salt stress.The concentration of Na⁺in muskmelon seedlings increased significantly under salt stress and significantly decreased the content of K⁺,and the ion balance in the plant was broken.ZNC increased the content of K⁺in muskmelon seedlings under salt stress,maintained cell turgor pressure,regulated the activity of transport protein,and reduced the content of Na⁺.