原花青素对设施连作土壤反硝化作用及黄瓜幼苗生长的影响OA

To investigate the effects of exogenous proanthocyanidin on soil denitrification in facility-grown cucumber monoculture systems and on the growth of cucumber seedlings,soil from plastic greenhouse where cucumbers had been continuously cultivated for nine years was sued as the experimental material.A control treatment(T0)without proanthocy-anidin(T0)was established,along with treatments in which proanthocyanidin were added at rates of to 0.5,1,2,and 3 g·kg-1 dry soil(designated as T0.5,T1,T2,and T3,respectively).The effects of proanthocyanidin on cucumber seedling growth,root nitrogen metabolism enzyme activities,denitrifying microbial community structure,and relative abundance of functional genes associated with denitrification were analyzed.The results demonstrated that compared with T0,the T2 treatment significantly promoted the growth of cucumber seedlings,increasing plant height,stem diameter,total root length,root surface area,and root volume by 25.5%,14.2%,101.27%,112.51%,and 214.56%,respectively.The addition of proanthocyanidin increased nitrogen content in both the aboveground biomass and roots of cucumber,as well as root ni-trogen metabolism enzyme activity.Specifically,the T2 treatment increased root nitrate nitrogen content by 171.52%.Fur-thermore,proanthocyanidin altered the community structure of denitrifying bacteria in the soil,reduced the abundance of related microbial populations,and inhibited nitrite reductase activity(NiR)and the relative abundance of its functional genes nirK and nirS,thereby increasing soil nitrate nitrogen content by 38.57%to 235.77%through the inhibition of deni-trification.Redundancy analysis(RDA)indicated that soil organic matter(SOM)and nitrate nitrogen content were signifi-cantly positively correlated with the denitrifying bacterial community.Pearson correlation analysis further demonstrated that soil environmental factors had a substantial influence on the abundance of denitrification functional genes.In conclu-sion,exogenous addition of proanthocyanidin can regulate soil nitrogen cycling by inhibiting denitrification,reduce ni-trate nitrogen loss,enhance plant nitrogen uptake,and consequently promote cucumber growth.