The Effects of Nitrogen and Phosphorus Deficiency on the Main Physiology of Ilex chinensis and Transcriptomic Analysis

The elements nitrogen (N) and phosphorus (P) are essential nutrients required for normal growth and photosynthesis in plants. However, nitrogen and phosphorus deficiencies can have a significant impact on plant physiology and metabolism. In this study, the two-year-old Ilex chinensis seedlings were used as the research object, the growth environment of low nitrogen (LN) and low phosphorus (LP) was simulated, and two treatment gradients of mild and severe stress were set up, and the changes of the growth and development of wintergreen and the main physiological indexes were studied under normal growth conditions as the control. Differentially expressed genes (DEGs) were identified by transcriptomic analysis at 10 weeks of severe stress. The results showed that nitrogen and phosphorus deficiency inhibited the growth of shoots and promoted root development of I. chinensis , and LN ₂ and LP ₂ treatments had the most serious effects. The physiological indexes showed that the contents of nitrate reductase (NR), glutamine synthetase (GS), superoxide dismutase (SOD) and peroxidase (POD) and malondialdehyde (MDA) in the LN ₂ group were significantly increased by 112.36%, 290.19%, 67.56%, 151.79% and 248.04%, respectively, compared with the CK group after 10 weeks of treatment. The activities of acid phosphatase (ACP), SOD and POD, anthocyanins and MDA increased by 77.1%, 65.46%, 97.81%, 144.43% and 134.25%. Transcriptome analysis revealed that the key differentially expressed genes under the nitrogen and phosphorus deficit of wintergreen were mainly involved in the regulation of plant growth, root development, nitrogen and phosphorus uptake and other biological processes. These findings provide insights into the adaptation mechanisms of I. chinensis under nitrogen and phosphorus deficits and highlight potential target genes for improving nutrient use efficiency. This study contributes to a better understanding of the physiological and molecular responses of I. chinensis to nitrogen and phosphorus deficiency stress, and provides valuable information for optimizing its cultivation under nutrient-constrained conditions.