Characteristics of absorption, distribution and utilization of 13C and 15N in young grape plants

Abstract: 【Objective】Carbon and nitrogen metabolisms play a very important role in plant life activities. Carbon and nitrogen metabolisms interact with and restrict each other. Carbon metabolism provides carbon source and energy for nitrogen metabolism, while nitrogen metabolism contributes to the synthesis of photosynthetic pigments and proteins including enzymes crucial for carbon metabolism.Both metabolisms need common carbon skeleton, ATP and reducing power. N fertilization not only promotes growth and biomass production, but also results in alterations in the allocation of resources and in plant morphology. Regulation of photosynthetic carbon metabolism is central for plant growth and development. The dynamic changes in carbon and nitrogen in plants directly affect the formation and transportation of photosynthetic products and the absorption and utilization of mineral elements. Carbon and nitrogen isotope tracing technique is an effective means to study the partitioning of the photosynthetic products and nitrogen nutrition. In recent years, stable carbon and nitrogen isotope tracing techniques have been applied to the study of the fate of photosynthetic products and the absorption, transport and distribution characteristics of nitrogen. This experiment focused on(1)13C abundance, content and distribution rate,(2) Ndff%,15N content, distribution rate, and utilization ratio and(3) the correlation among the indexes of young grape plants at different sampling times, and explored the changes in carbon and nitrogen uptake, distribution and utilization in different organs at different time after ammonium nitrogen application.【Methods】In this study, we applied 300 mg(~(15)NH4)2 SO4 to two-year-old grape(Vitis vinifera L.'Red Globe') young plants, labeled13C at 15 d, 30 d, 45 d and 160 d after nitrogen application and sampled at 72 h after13C labeling.【Results】The biomass of new organs(new roots,leaves and new branches) increased significantly with time. At 45 d, the new root biomass increased by410.34% and 60.87% at 15 and 30 d, respectively, and the biomass of new branches by 397.22% at 160 d compared with 45 d. The biomass of roots and old shoots did not change significantly from day 15 to day 45, but increased significantly by 160 d. The13C abundance in the new roots, leaves and new shoots was significantly higher than in the old roots and old shoots, with the new roots having the highest abundance. The content of13C in the new root was the highest at 15 days after nitrogen application, followed by the leaves. Leaves had the highest content from 30 d. The carbon content in the new branch and old root had increased significantly by 160 d. The13C allocated to the new roots and leaves was high,13C allocated to the new roots being 1.37 times that to the leaves at 15 days after nitrogen application. From30 to 160 days,13C allocated to the leaves was 18.04% to 104.97% higher than to the new roots. The distribution rate in the new roots and old roots had increased significantly by 160 d. After application of nitrogen, the Ndff of each organ reached the maximum at 45 d. Nitrogen recruitment in the new organs was significantly higher than in the old branches and in the old roots, and the new roots had the highest nitrogen recruitment. After nitrogen application, the amount of nitrogen in the leaves was the highest throughout the experiment. The amount of nitrogen in the new roots increased significantly in the early stage. By day 30 and day 45 it had increased by 9.48 times and 1.17 times compared with the previous sampling day, respectively. The nitrogen content in the new branches at 160 d had increased by 19.80 times compared with that at 45 d. The distribution rate of nitrogen applied in the leaves was significantly higher than in the other organs. The distribution rate in the new roots increased first, reached the highest at 45 d, and then decreased. There was no significant difference in the distribution rate compared with the new branches, in which it had increased significantly by 160 d and was 8.30 times higher than that at 45 d. During day 15-30, the leaf nitrogen utilization rate was the highest, followed by the root system. The nitrogen utilization rate in all organs except for the new branch reached the highest values at 45 d. The utilization rate in the new branch had increased significantly by 80.13% by 160 d. There was significant positive correlations between grape biomass and13C content(r=0.578**) and15N content(r=0.657**), between13C content and15N content(r=0.708**), and between the13C allocation rate and the15N distribution rate(r=0.501**).【Conclusion】Nitrogen application promotes the absorption and distribution of carbon nutrients in the new organs, as well as the absorption, distribution and utilization of nitrogen nutrients. The distribution of carbon and nitrogen in plants is mutually influenced and mutually restrictive. The carbon-nitrogen cycle is also an interactive and coupled process.