Responses Of Enzyme Activities To Nitrogen Addition In The Leaves Of Larch From The Greater Khingan Mountains

At present,most of the studies on the effects of nitrogen nutrition and photosynthesis in plants indicate that nitrogen addition will increase the nitrogen content in leaves,and the result will increase the net photosynthetic rate of plants,while excessive nitrogen deposition will reduce the photosynthetic rate.However,the response mechanism of leaf enzyme to nitrogen addition is insufficient.A study on Larix gmelinii in Daxing'anling is carried out.Establishment of four nitrogen(Nitrogen,N)level treated plots with unified site conditions,control(CK,0g N m^-2a^-1),low nitrogen(LN,2.5g N m^-2a^-1),medium nitrogen(MN,5g N m^-2a^-1),high nitrogen(HN,7.5g N m^-2a^-1)four nitrogen levels were treated.Selective selection of Larix gmelinii,and determine photosynthetic rate(Photosynthetic rate,Pn)of fresh leaves,chlorophyll(chlorophyll),nitrogen content,carbon content(carbon,C),enzyme activity of ribulose-1,5-Diphosphate carboxy/oxygenase(ribulose bisphosphate carboxylase/oxygenase,Rubisco),enzyme activity of 3-glyoxal phosphate dehydrogenase(glyceraldehyde-3-phosphate dehydrogenase,GAPDH),enzyme activity of fructose-1,6-bisphosphate phosphatase(fructose-1,6-bisphosphate phosphatase,FBPase),enzyme activity of glycolate oxidase(glycolate oxidase,GO),at different nitrogen levels.The purpose of this study is to explain the effect of nitrogen addition on leaf enzyme and the physiological mechanism of leaf enzyme activity on photosynthesis,so as to provide ideas and think about the physiological mechanism of nitrogen-leaf enzyme activity-photosynthesis interaction in the future.The main findings are as follows:(1)With increased nitrogen levels,blade nitrogen content increased and high nitrogen significantly.(2)With the increase of nitrogen application level,chlorophyll content increased gradually.The linear relationship between nitrogen application and chlorophyll content.The chlorophyll content under HN treatment was significantly higher than that under other treatments,and the chlorophyll content under CK treatment was significantly lower than that under other treatments.(3)As the nitrogen application level increases,the photosynthetic rate rises first and then decreases.The photosynthetic rate gradually increased from control to MN treatment,showing a downward trend at high nitrogen treatment.The photosynthetic rate under MN is higher than other processes and high nitrogen is lower than other processes.(4)With the increase of nitrogen application level,the enzyme activity of GO increased gradually,and the enzyme activity of Rubisco,the enzyme activity of GAPDH,the enzyme activity of FBPase all increased first and then decreased.The enzyme activity of Rubisco,the enzyme activity of GAPDH increased gradually,and was significantly higher than that of other treatments.The enzyme activity of FBPase gradually increased,to low nitrogen treatment significantly higher than other treatments..The GO enzyme activity under HN treatment was significantly higher than that under other treatments.(5)There was significant positive correlation between chlorophyll content,photosynthetic rate and Rubisco enzyme activity in CK?LN?MN treatment.The enzyme activity of Rubisco was also positively correlated with the enzyme activity of GAPDH during CK treatment.The enzyme activity of FBPase was positively correlated with chlorophyll content,photosynthetic rate and Rubisco activity,respectively.The enzyme activity of FBPase was negatively correlated with chlorophyll content,photosynthetic rate and Rubisco activity,respectively.The photosynthetic rate was positively correlated with chlorophyll content and Rubisco enzyme activity,respectively.There was significant negative correlation between GO activity and chlorophyll content,photosynthetic rate and Rubisco activity.