Abstract:

Non-structural carbohydrates （NSC）， as the core carbon source for plant stress responses， perform dual functions of osmotic regulation and metabolic energy supply. In this study， Ammopiptanthus mongolicus seedlings were used as experimental materials to simulate continuous drought stress. The physiological processes and dynamic changes of NSC in roots， stems， and leaves were monitored， and the coupling relationship between NSC metabolism and physiological decline was analyzed via principal component analysis （PCA）. The results showed that： the relative water content （RWC） and photosynthetic rate of leaves approached 0 at 20-24 days of drought， indicating the loss of photosynthetic function； root soluble sugars （RSS） increased continuously， stem soluble sugars （SSS） increased first and then decreased， leaf soluble sugars （LSS） decreased sharply in the later stage； starch remained stable in the roots， initially increases and then decreases in the stems， and continuously declines in the leaves， with a reduction rate of up to 73.80%. With the intensification of drought， the intraspecific NSC allocation shifted from leaf-dominated （64%） to root-dominated （52%） before death. PCA revealed that photosynthetic-water variables were positively correlated with leaf NSC but negatively correlated with root NSC， reflecting the carbon resource trade-off of aboveground growth-underground survival. This study demonstrated that Ammopiptanthus mongolicus delays drought-induced mortality by regulating the metabolic and allocation strategies of NSC among organs， and the synchronous exacerbation of NSC metabolic imbalance and physiological function decline may be the key mechanism triggering death.

Key words: Ammopiptanthus mongolicus, drought-indu ced lethality, photosynthetic physiology, non-structural carbohydrates, metabolic dynamics