Effects of biochar combined with nitrogen on physiology and ecology of Paulownia fortunei seedlings under Cd stress
[Objective]The study aimed to explore the effects of biochar combined with nitrogen on morphological characteristics,root mor-phology,antioxidant activity,photosynthetic characteristics and Cd accumulation,accumulation and transport of Paulowniafortunei seedlings under Cd stress.[Method]Taking'Paulownia fortunei 1201'seedlings as materials,a combination of tissue culture and hydroculture tests was set up.The growth index,root parameters,photosynthetic gas parameters,antioxidant enzyme activity,MDA content,Cd accumula-tion,enrichment coefficient and transport coefficient of seedlings were measured by biochar and nitrogen single treatment and biochar com-bined with nitrogen treatment.[Result](i)Under Cd stress,application of biochar and nitrogen could significantly increase plant height,biomass and root parameters,and their combination could achieve the optimal effect.(ii)SOD and CAT activities increased and MDA activ-ities decreased in leaves and roots of Paulownia fortunei seedlings,POD activity decreased with increasing concentration under single appli-cation of biochar and nitrogen,and slightly increased with increasing concentration under combined application of biochar and nitrogen.(iii)Chla,Chlb and Chl(a+b)increased significantly,but Chl(a/b)had no significant change;Photosynthetic gas parameters(Pn,Tr,Ci,Gs)increased,WUE was the highest,and Ls decreased significantly.(iv)With the application of biochar or nitrogen,the Cd content and enrichment coefficient of Paulowniafortunei seedlings decreased,while the transport coefficient and Cd accumulation increased.(v)Accord-ing to the correlation and PC A analysis of each index of seedlings,it was found that there was correlation among each index,and the overall promoting effect was biochar combined with nitrogen＞biochar＞nitrogen.[Conclusion]The application of biochar and nitrogen can im-prove the photosynthetic capacity of Paulownia fortunei seedlings,reduce the absorption of Cd,alleviate the toxicity of Cd,and then increase the biomass and promote the accumulation of Cd in various organs.
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