氮素营养水平对膜下滴灌玉米穗位叶光合及氮代谢酶活性的影响

Abstract

Jilin Province is the main maize-producing province in China but frequently suffers from drought. Western parts of the province,such as Baicheng and Songyuan,do not receive sufficient rainfall to support increased agricultural production,which severely limits enhancement of maize yield. A project to install drip irrigation to one million acres was initiated in the province,which is important for improving the drought resistance and yield of maize. Nitrogen,as the most important element for maize growth,has a major impact on yield and physiological characteristics. For maize cultivated with under-mulch drip irrigation with dual lines per ridge,what influence will the nitrogen nutrition level have on photosynthesis by the ear leaf and related physiological characteristics? To address this question,maize Xianyu420 was used as the test material and five nitrogen nutrition levels were applied. Starting !from the silking stage,on each morning at 09: 00—11: 00 for 10 days,six representative plants of uniform growth were selected from each treatment and the following photosynthesis parameters were measured: ear leaf net rate of photosynthesis( P n),transpiration rate( T r),stomatal conductance( g s), water use efficiency( WUE),maximum photochemical efficiency( F v / F m),actual photochemical efficiency( Φ PSⅡ), photochemical quenching( q P),nitrogen content,and the activities of phosphoenolpyruvate( PEP) and ribulose 1,5-biphosphate( RUBP) carboxylase,proteolytic enzymes( endopeptidase and aminopeptidase),nitrate reductase( NR),and glutamine synthetase( GS). The influence of nitrogen level on photosynthesis characteristics and activity of key enzymes involved in nitrogen metabolism in the ear leaf was studied with under-mulch drip irrigation with dual lines per ridge. The results showed that the average values for ear leaf nitrogen content,P n,T r,g s WUE,F v / F m,Φ PSⅡ and q P were highest in the N3 treatment( 300 kg N / hm2). The response of PEP carboxylase activity to nitrogen fertilizer application was more sensitive than that of RUBP carboxylase activity. When nitrogen fertilizer application was less than 100 kg N / hm2,RUBP carboxylase activity was significantly reduced. Application of nitrogen fertilizer increased the activity of NR and GS in the ear leaf. And the highest increases in NR and GS activity were recorded in the N3 treatment. Proteolytic activity showed the opposite response. The nitrogen content of the ear leaf was negatively correlated with endopeptidase and aminopeptidase activity,and positively correlated with all other indicators of photosynthetic activity. In the study area,when the total amount of nitrogen fertilizer applied is 300 kg / hm2,the ear leaf of maize maintains higher photosynthetic parameters and relevant enzyme activity and provides the foundation for increased grain yield. Adequate supply of nitrogen fertilizer can ensure smooth and efficient activity of enzymes involved in nitrogen metabolism in leaves of maize.