马桑结瘤固氮与光合作用的关系

马桑(Coriaria sinica)植株的结瘤量、根瘤固氮活性和固氮能力均与植株叶面积和光合能力呈显著的直线相关关系，叶面积大、光合能力强的植株结瘤量大，根瘤固氮活性高，固氮能力强。马桑根瘤固氮活性呈白天升高夜间降低的昼夜变化特点，昼夜变幅为10～20μmol C2H2/g.h，光合作用是引起固氮活性昼夜变化的主要因素，同时受土壤温湿度的影响，遮阴或光照不足将引起马桑结瘤固氮能力的大幅度降低。

Relationship between nitrogen fixation and photosynthesis of Coriaria sinica

Nodulation, Nfixing activity and total nitrogen fixation per plant of Coriaria sinica were positively correlated with leaf area and photosynthesis per plant of the host. The host with higher leaf area and capacity of photosynthesis had a higher capacity of nitrogen fixation with higher nodule and N\|fixing activity. N\|fixing activity of C. Sinica nodule showed a daily variation model with a higher level (20.2μmol C2H2/g.h) in the day and a lower level (9.2μmol C2H2/g.h) in the night. The diurnal fluctuation in N\|fixing activity of C. Sinica seedling nodule was demonstrated mainly ascribed to photosynthesis of the host by an experiment, in which soil temperature variation was hold within 3.2℃ (20±1.6℃), and nearly 2 fold increase (10～19μmolC2H2/g.h) in acetylene reduction by C. Sinica nodule at midday compared with midnight was measured. However, changes in soil temperature and moisture appeared to be the important factors affecting daily changes in N\|fixing activity of C. Sinica seedling nodule. Shade or shortage of light made the N\|fixing activity reduced largely due to the decreased photosynthetic rate of the host. When light was shaded by 40% by seven days, photosynthetic rate and N-fixing activity of C. Sinica reduced by 26.56% and 25.96%. When light was shaded by 70%, photosynthetic rate and N-fixing activity reduced by 38.02% and 79.43%.