Abstract: Aims Exploring the interactions between non-structural carbohydrates (NSC) allocation patterns and photosynthetic properties of different age classes of Artemisia ordosica under drought stress cannot only reveal the evolution of drought-resistant strategies during individual plant development but also provide theoretical support for predicting the dynamics of desert vegetation and formulating differentiated ecological restoration strategies in the context of climate change. Methods A. ordosica, a typical sandy plant in desert areas, was used as the research object. Four rainfall gradients were set up through a field precipitation control experiment to simulate the normal (natural precipitation); mild drought (30% rainfall reduction); moderate drought (50% rainfall reduction); and extreme drought (70% rainfall reduction) conditions for A. ordosica. Based on its morphological characteristics, we classified the age classes of A. ordosica (low, medium, and high) and measured the photosynthesis-related parameters as well as the NSC content in leaves and twigs of plants from these different age classes. Important findings Our main results showed that: (1) Mild drought did not affect photosynthetic carbon assimilation in A. ordosica, while moderate and extreme drought significantly suppressed it. (2) A. ordosica dynamically replenishes photosynthetic losses through organ-specific partitioning of NSC. Twigs rapidly responded to mild drought stress through significant soluble sugar accumulation and starch depletion. During moderate to extreme drought conditions, twig starch reserves recovered substantially while leaf soluble sugars maintained accumulation, with osmotic regulation sustained through starch hydrolysis. (3) Structural equation modeling (SEM) analysis demonstrated that drought's direct positive effects on twig and leaf NSC (β=0.78 and 0.90, respectively) substantially counteracted the indirect photosynthetic inhibition effects (β=-0.87 and -0.27), revealing this species' survival strategy of actively modulating carbohydrates’ allocation through the non-photosynthetic pathways under drought stress.

Key words: Artemisia ordosica, age class, drought stress, non-structural carbohydrates, photosynthetic properties