Effects Of Different Nitrogen Forms And Ratios On Growth Characteristics Of Phyllostachys Edulis And Evergreen Broad-leaved Forest Species Seedlings

In order to test the preference for inorganic nitrogen（NO₃^--N/NH₄⁺-N）of Phyllostachys edulis,Schima superba,Cinnamomum camphora and Quercus glaucaseedlings,we conducted the experiments in hydroponic culture and pot culture.Physiological characteristics and enzymes activities of plants,physicochemical properties and enzymes activities of rhizosphere soil under different forms and ratios of inorganic nitrogen were investigated.The experimental treatments included five different ratios of NH₄⁺-N:NO₃^--N（0:100;25:75;50:50;75:25;100:0）in hydroponic culture.The results showed that there were significant effects of different nitrogen forms and ratios on growth characteristics of Phyllostachys edulis and Quercus glauca seedlings.The SPAD value,root length,root surface area and NRA of Phyllostachys edulis seedlings were highest in the treatment with theratio of 75:25.And the root length and root surface area of Cyclobalanopsis glauca seedlings were highest in the treatment with the ratio of 25:75.The SPAD value of Cyclobalanopsis glauca was significantly higher in the treatment with the sole nitrogen source（0:100）than other treatments.The NRA in roots of Cyclobalanopsis glauca was positively correlated with nitrate concentration in nutrient solution.However,the above correlation was not observed for Phyllostachys edulis seedlings.These findings indicated that Phyllostachys pubescens might show its preference in absorbing ammonium nitrogen at seedling stage,while Cyclobalanopsis glauca might show its preference in absorbing nitrate nitrogen.The experimental treatments included three different ratios of NH₄⁺-N:NO₃^--N（25:75;50:50;75:25）in soilinpot culture.The results showed that there were significant effects of different nitrogen forms and ratios on growth characteristics of different plants.We find that plant biomass,SPAD value and glutamine synthase activity increased with increasing concentration of ammonium,while soil pH was significant decreased in rhizosphere soil of Phyllostachys edulis.The biomass of C.glauca,S.superba and C.camphora,SPAD value of C.camphora and C.glauca,intercellular carbon dioxide concentration of S.superba and C.glauca,and NRA significantly increased with increasing concentration of nitrate.As compared to other treatments,the photosynthetic characteristics and urease activities of four plant spices were obviously improved under the treatment of the ratio of 50:50.In summary,there were significant different in the absorption and growth characteristics of ammonium and nitrate of Phyllostachys edulis and subtropical evergreen broadleaf tree species including S.superba,C.camphora and C.glauca.When nitrogen forms were dominated by ammonium nitrogen,P.edulis showed its preference in absorbing ammonium nitrogen at seedling stage than broadleaf species,while S.superba,C.camphora and C.glauca might show its preference in absorbing nitrate nitrogen.