Carbon-Nitrogen Metabolic Responses And Adaptive Strategies To Low-Nitrogen Stress In Glycine Soja

Wild soybean（Glycine Soja）is an important wild resource plant with many excellent characters,which has strong resistance and wide adaptability to adverse environment,and is also an excellent experimental material for the study of low nitrogen tolerance mechanism,which has certain application value in realizing the improvement of cultivated soybean varieties and increasing grain production.The study of basic metabolism and physiology of wild soybean and the understanding of its mechanism of low nitrogen tolerance are of great significance for the protection of wild soybean germplasm resources and the rational exploitation of endangered wild plant resources.In our study,two varieties of wild bean seedlings（common wild soybean W1 and low-nitrogen-tolerant wild soybean W2）were selected as experimental materials to simulate three kinds of low nitrogen stress environments with different intensities,in order to explore the physiological differences of seedling growth characteristics,photosynthetic carbon metabolism,nitrogen metabolism and carbon and nitrogen metabolism.The adaptive physiological mechanism of tolerance to low nitrogen in wild soybean was revealed,and the evolution process of basic metabolism and physiological plasticity of wild soybean in the process of adaptation ecological environment selection was understood,which provided physiological reference for protecting the rational and utilizing wild soybean germplasm resources.The experimental results showed that the two wild soybeans showed some resistance under different intensity low nitrogen stress,but under high intensity low nitrogen stress,the nitrogen-tolerant wild soybean alleviated the inhibition of low nitrogen stress on growth by maintaining high root length,root-shoot ratio and relative growth rate.Nitrogen-tolerant wild soybeans were able to accumulate more Mn²⁺、SO₄^2-and Ca²⁺in the roots by regulating the ionic equilibrium between the roots and leaves,maintaining a high absorption capacity of K⁺and Mg²⁺in the leaves.By comparing the photosynthesis parameters of the leaves of the two ecotype wild soybean seedlings,the content of carotenoids in the leaves of nitrogen-tolerant wild soybean increased gradually and the soluble sugar in the roots accumulated gradually with the increase of low nitrogen stress.Under low nitrogen stress,the photosynthetic assimilation capability of nitrogen-tolerant wild soybean is much steadier,and its photosynthetic capacity is larger than that of common wild soybean.Analysis of nitrogen metabolism related enzyme activity in leaves of two kinds of wild soybean seedlings showed that under low intensity low nitrogen stress treatment,compared with control group,the activity of nitrogen metabolism related enzyme in leaves of two wild soybean reduced,and with the increase of stress intensity,the decrease of common wild soybean was greater than that of nitrogen-tolerant wild soybean.Under high intensity low nitrogen stress,high soluble protein content was maintained in nitrogen-tolerant soybean leaves.The experimental results showed that the nitrogen-tolerant wild soybean was able to maintain high nitrogen metabolic enzyme activity and expression and maintain C-N assimilation balance to resist low nitrogen stress.In this study,the physiological response of wild soybean seedings under low nitrogen stress was closely related to the coupling of carbon and nitrogen metabolism,which provided a valuable basis for exploring the response of nitrogen-tolerant wild soybean to low nitrogen stress.