Effects of drought stress and Ca supply on photosynthesis, fluorescence parameters and growth of Glycyrrhiza uralensis in the Hexi Corridor.

Calcium (Ca) functions as a secondary messenger and contributes to plant drought tolerance. This study examined how Ca supplementation influences photosynthetic performance and growth in Glycyrrhiza uralensis seedlings under drought stress. Drought significantly reduced net photosynthetic rate, stomatal conductance, and transpiration rate. Under severe drought, photosynthesis was primarily constrained by non-stomatal limitations, indicating damage to the photosynthetic apparatus. Ca supplementation partially restored gas exchange and alleviated drought-induced photoinhibition by mitigating the decline in maximum PSII efficiency. Drought also reduced growth and root yield (plant height, basal diameter, crown area, root length), whereas Ca supplementation promoted seedling growth and alleviated drought-related damage, thereby enhancing overall drought adaptability. These findings demonstrate that Ca plays a key role in maintaining photosynthetic function and alleviating photodamage under water-limited conditions. Appropriate Ca supplementation may therefore serve as a practical strategy to improve drought tolerance and support the sustainable cultivation of G. uralensis in arid and semi-arid regions.