氮素对荒漠C3植物异养器官富集13C的调控机制

与自养器官相比，C3植物异养器官相对富集13C，这一普遍现象在60年前就已首次报道。由于对植物后光合代谢过程未完全了解，导致目前C3植物异养器官富集13C的机制尚不清楚。为证实养分能够通过后光合代谢调控C3植物异养器官富集13C，本项目拟从氮素研究入手，以油蒿、红砂、白刺、四合木、半日花5种荒漠C3植物为对象，采用整株挖掘法和稳定同位素分析方法测定每种植物叶片、花、种子、茎、树皮、粗根和细根的氮含量和δ13C，通过对异养器官氮含量与Δ13Corgan分析，揭示C3植物异养器官氮素调控Δ13Corgan的生理过程；通过测定5种植物叶片δ13C、氮含量和光合生理指标的季节变化，分析三者间的关系，探讨叶片碳同位素分馏差异的原因，重点揭示C3植物叶片氮素调控异养器官Δ13Corgan的生理过程，构建氮素调控C3植物异养器官富集13C的生理机制，为解决C3植物异养器官富集13C指出一个新的方向。

Heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) in C3 plant species. This universal phenomenon was first reported 60 years ago. Currently control mechanism of heterotrophic organs 13C enrichment in C3 plant is unclear since deficiencies in understanding post-photosynthetic metabolic processes. We hypothesize that nutrients may control heterotrophic organs 13C enrichment in C3 plant in post-photosynthetic metabolic processes. Here, we excavated five desert C3 plant species of whole plant architectures, including Artemisia ordosica Krasch, Reaumuria soongarica (Pall.) Maxim., Nitraria tangutorum Bobrov, Tetraena mongolica Maxim., Helianthemum songaricum Schrenk. We will systematically and simultaneously measure nitrogen concentrations and carbon isotopic ratios (δ13C) of different parts of the excavated plants (coarse roots, fine roots, stems, barks, leaves, flowers, seeds) using the whole plant excavation method and stable isotope analysis methods, and then we analyzed the relationship between nitrogen content and Δ13Corgan in heterotrophic organs to reveal the physiological process of nitrogen control Δ13Corgan in heterotrophic organs of C3 plant. Meanwhile, we also determined the seasonal variations of the five kinds of plants in leaf carbon isotopic ratios, photosynthetic physiology parameters and nitrogen concentrations, analyzed the seasonal dynamic relationship among the three indexes and discussed the physiological processes of carbon isotopic difference occurring inside leaves. Present study primarily revealed physiological processes of nitrogen control of Δ13Corgan in heterotrophic organs and discovered preliminarily physiological mechanisms of nitrogen control heterotrophic organ 13C enrichment in C3 plants. In addition, this studies also pointing to a new direction to explain heterotrophic organs 13C enrichment in desert C3 plants.