Comparative Morpho-Physiological and Biochemical Responses of Waterleaf (Talinum fruticosum) to Drought and Waterlogging Stresses

Waterleaf (Talinum fruticosum) is an underutilized leafy vegetable with recognized tolerance to environmental stresses, yet comprehensive characterization of its morpho-physiological and biochemical responses to contrasting water stress conditions remains limited. This study aimed to evaluate the morphological, physiological, and biochemical responses of waterleaf to continuous drought and waterlogging stress, and to examine trait interrelationships under each stress using correlation analyses, providing exploratory insights into coordinated stress responses. The experiment was conducted under controlled greenhouse conditions using a completely randomized design. Plants were subjected to three watering regimes: well-watered control, continuous flooding, and severe drought (≤10% field capacity). Drought stress induced more severe growth suppression than waterlogging, with reductions of 3.8-fold in leaf area and 5.5-fold in flower production compared to control. Net photosynthetic rate declined by 5.7-fold under drought and 3.1-fold under waterlogging, accompanied by corresponding reductions in stomatal conductance and transpiration rate. Proline accumulation was substantially enhanced under drought (3.6-fold increase), while soluble sugars increased by 1.7-fold. Total phenolics and flavonoids increased by 1.8-fold and 1.7-fold, respectively, under drought stress, with more moderate increases under waterlogging. Oxidative stress markers, including malondialdehyde (3.4-fold increase) and hydrogen peroxide (2.9-fold increase), were significantly elevated under drought compared to waterlogging. Correlation analyses revealed stronger and more numerous interrelationships among traits under drought stress, indicating a more coordinated and integrated stress response. The findings demonstrate that waterleaf exhibits differential sensitivity to drought and waterlogging, with drought imposing more severe constraints on growth, photosynthesis, and reproductive output. The stress-induced accumulation of phenolic compounds and enhanced antioxidant capacity suggests that controlled water stress may influence the phytochemical profile of waterleaf, presenting opportunities for further research to optimize irrigation practices for balancing yield and quality in sustainable production systems.