Lead Stress On Nitrogen Assimilation And Photosynthetic Nitrogen Allocation In Toona Ciliata Roem.and Cinnamomum Camphora (L.) Presl

So far, the mechanism that lead stress on plant photosynthesis is unclear. In order to research the pathway that lead stress on photosynthesis is based on lead stress on the nitrogen metabolism and photosynthetic nitrogen distribution pattern in plants. This experiments take advantage of two common landscape plants to explore the results. In the experiments, the Toona ciliata Roem. and Cinnamomum camphora (L.) Presl. are put in different concentration of lead (0,50,200,400,800mgkg-1soil). Under the stress, we test the changes of photosynthetic physiological. The test focus on the relationship among nitrogen absorption, photosynthetic nitrogen distribution and photosynthesis. The purpose is to study the pathway that lead stress on photosynthesis is based on that lead stress on nitrogen cycle.The findings are as following:1) Under different concentration of lead, the activity of key enzymes in nitrogen metabolism NR and GS and the organic nitrogen content NW and NM were inhibited in Toona ciliata Roem. and Cinnamomum camphora (L.) Presl.2) With the influences of different lead concentration, the fraction of lead nitrogen is allocated to different components of photosynthetic machinery(PC, PB, PL and PT) and the the fraction of lead nitrogen content(NC, NB, NL and NP) were changed in Toona ciliata Roem. and Cinnamomum camphora (L.) Presl. in different degrees. And both two kind of plants reduce the fraction of leaf nitrogen allocated to carboxylation PC and distribute them in the fraction of leaf nitrogen allocated to bioenergetics PB and light-harvesting components PL. The difference between them is that Toona ciliata Roem. gives more nitrogen to PL and less to PB to reduce the damage of lead poison, and Cinnamomum camphora (L.) Presl. is balanced the growth of PL and PB to protect itself.3) With the rise of different concentration of lead, the photosynthesis, photosynthetic pigment(CC, Chla, Chlb, Chlr and Chla/b), photosynthetic parameters(Jmax, Vcmax and Rd) were inhibited by lead, and the photosynthetic nitrogen utilization efficiency PNUE were changed.4) Nitrogen is a large number of elements that is needed to make plants grow. And nitrogen metabolism and photosynthetic nitrogen distribution has significant meaning to the plants in photosynthesis. By comparing the correlation analysis shows that:Lead stress on photosynthetic physiology based on the influence of nitrogen metabolism and photosynthetic nitrogen distribution.In conclusion, lead stress on photosynthesis by influencing the activity of key enzyme NR and GS in nitrogen metabolism, further photosynthetic nitrogen distribution pattern (PC was maximum), photosynthetic pigments, the leaf nitrogen content, the photosynthetic correlation coefficient, the photosynthetic nitrogen utilization efficiency PNUE, special leaf area SLA, and finally the normal photosynthesis in two species. The results has tested the pathway that lead stress on photosynthesis in plants is based on lead stress on nitrogen metabolism and the photosynthetic nitrogen distribution pattern. And the purpose of this experiment is to offer a way to solve the problem and provides a way based on nitrogen cycle to improve the pollution of soil polluted by lead. Ultimately, it supplies an new cultivation, planting and landscape gardening advice and theoretical basis.