Saline-Alkali Stress Influences Ecological Stoichiometric Homeostasis of Manganese and Zinc in Leymus chinensis

Soil salinization is a major environmental issue that adversely affects plant growth and nutrient balance, posing challenges to sustainable agriculture. Understanding how plants regulate essential trace elements under saline-alkali stress is crucial for improving stress tolerance and ecosystem stability. The ecological stoichiometric homeostasis of Leymus chinensis ( L. chinensis ) in relation to the trace elements manganese (Mn) and zinc (Zn) under saline-alkali stress remains unclear. Mn and Zn are vital for photosynthesis, enzyme activation, and antioxidant defense, and are often deficient in Northeast China’s saline-alkaline soils; thus, their balance affects plant tolerance and nutrient uptake under saline-alkali stress, making homeostatic regulation essential for resilience and productivity. The effects of Mn and Zn addition under different saline-alkali stress levels on their homeostasis in L. chinensis were examined. Under different saline-alkali conditions with Mn and Zn addition, aboveground Mn and belowground Zn conformed to the homeostasis model, indicating stabilized regulation of Mn in shoots and Zn in roots. However, the homeostasis indices for both Mn and Zn were greater in the aboveground than in the belowground parts of L. chinensis , indicating stronger overall homeostatic strength in shoots. The addition of high concentrations of Mn (Mn = 2 mmol L −1 ) and Zn (Zn > 0.8 mmol L −1 ) significantly increased Mn and Zn in L. chinensis . Excessive Mn and Zn supply was not beneficial for maintaining homeostatic control, leading to Mn and Zn imbalance in L. chinensis . This study suggests that adding 0.75–1.5 mmol L −1 Mn and 0.4–0.6 mmol L −1 Zn is optimal for maintaining Mn and Zn content and homeostasis in L. chinensis . Identifying these optimal ranges is important for formulating targeted micronutrient management strategies to enhance the resilience of L. chinensis in saline-alkali degraded grasslands characterized by Mn and Zn deficiency.