不同土壤pH和铵硝态氮配比对杉木和木荷幼苗生理特性及各器官氮含量的影响

[Objective]In the context of soil acidification and nitrogen(N)deficiency and the intensification of heterogeneous distribution environment,to investigate the effects and differences of different soil pH and ratios of ammonium to nitrate on the physiological characteristics and root,stalk,and leaf N content of seedlings of the subtropical major coniferous tree,Cunninghamia lanceolata,and broadleaf tree,Schima superba,which can provide a scientific basis for the screening of the optimal environment for the growth of the two species in soil pH and nitrogen form ratios.[Methods]In this study,two pH levels(pH1=4.5 and pH2=6.5)and five ratios of ammonium to nitrate(NH4+-N∶NO3+-N∶10∶0,7∶3,3∶7,0∶10,5∶5)were used in the simulation of the nutrient environments with different pH and ratios of ammonium to nitrate for the seedlings of C.lanceolata and S.superba.In order to analyze and compare the differences in physiological characteristics and N uptake and utilization efficiency of the seedlings of the two species,we used the following methods.[Results](1)Under the 2 pH treatments,the MDA content,SOD,POD,and CAT activities of C.lanceolata leaves and POD activities of leaves of S.superba seedlings showed higher levels at pH=4.5 than at pH=6.5.Under the five ratios of ammonium to nitrate treatments,SOD,POD,and CAT activities increased with increasing nitrate-N concentration in the treatments for C.lanceolata,and with increasing ammonium-N concentration in the treatments for S.superba.(2)Under the two pH treatments,pH=4.5 significantly inhibited the activities of the key enzymes of nitrogen metabolism GS,GOGAT,NR and NiR in C.lanceolata and S.superba,inhibited the assimilation and utilization of ammonium nitrogen and uptake of nitrate nitrogen by C.lanceolata seedlings,and inhibited nitrate nitrogen and ammonium nitrogen uptake by S.superba seedlings;and reduced the total nitrogen accumulation in the organs of the seedlings of the two tree species.Under the three treatments with the ratios of ammonium-nitrate nitrogen of 10∶0,0∶10,and 5∶5,the single ammonium nitrogen treatment significantly increased the GS,GOGAT,NR,and NiR activities of C.lanceolata leaves as a whole compared to the single nitrate nitrogen treatment.pH=4.5 level,the GS,GOGAT,NR,and NiR activities of S.superba were higher in the single ammonium nitrogen treatment,and pH=6.5 level,the Single ammonium nitrogen treatment increased GS activity and single nitrate nitrogen treatment increased NiR activity of woodhorn.The ammonium nitrogen content of C.lanceolata leaves was higher than that of higher ammonium nitrogen concentrations at the higher nitrate nitrogen concentration ratios,and the nitrate nitrogen content did not differ significantly among ratios;the ammonium nitrogen and nitrate nitrogen contents of S.superba leaves as a whole were higher than those of higher nitrate nitrogen concentrations at higher ammonium nitrogen concentration ratios.(3)Nitrogen accumulation in the organs of C.lanceolata seedlings was greater at higher ammonium nitrogen concentration ratios,while nitrogen accumulation in the organs of S.superba was greater at higher nitrate nitrogen concentration ratios.[Conclusion]The pH=4.5 of the cultivation substrate was unfavorable to the growth of C.lanceolata and S.superba seedlings,and the seedlings of the two species showed different nitrogen uptake preferences during cultivation,i.e.,the high ammonium nitrogen ration was suitable for the growth of C.lanceolata seedlings,and the high nitrate nitrogen ration was suitable for the growth of S.superba seedlings.