Mild and moderate drought stress enhances resilience in Syzygium cumini seedlings by modulating physio-biochemical attributes

As climate change intensifies, understanding how Syzygium cumini (L.) Skeels (Jamun), a species vital for both ecology and horticulture, responds to drought stress is crucial for ensuring its survival and productivity. The critical question was whether the species exhibits adaptive or resilient responses or typical drought stress symptoms under varying irrigation schemes. Thus, the study aimed to evaluate the morpho-physio-biochemical and nutrient uptake traits of jamun seedlings under different stress conditions: 100% field capacity $${(F}_{wc}$$ ) (control), 75% (mild stress), 50% (moderate stress), and 25% (severe stress). Increasing the drought intensity significantly exacerbated drought stress symptoms, such as reduced stem height, diameter, leaf area, and leaf number, while root length and root–shoot ratio progressively increased. Physiological functions were impaired by drought evidenced by decreased photosynthesis, transpiration, chlorophyll, and an increase in electrolyte leakage. Under severe stress, photosynthesis, stomatal conductance, and transpiration decreased by 95%, 88%, and 89%, respectively, compared to the control. However, stomatal density and water use efficiency (WUE) showed a biphasic response; both initially increased under moderate stress as an adaptive response to optimize gas exchange, conserve water, but declined under severe stress, likely due to cellular damage. A prolonged water deficit led to a 21% increase in electrolyte leakage compared to the control. Consequently, oxidative stress was markedly elevated, with hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels rising by 276% and 210% respectively, under severe water deficit conditions. Despite moderate and severe stresses, plants survived, potentially by triggering water conservation strategies such as increased osmolytes accumulation and enhanced WUE accompanied by reduced transpiration rate and increased relative water content (RWC) in moderate stress. Accumulation of proline increased by 50% and 176% under moderate and severe water stress, respectively compared to the control. RWC decreased by 10% and 50% under moderate and severe water stress. Foliar macronutrient concentrations (N, P, K, Mg, Ca, and S) decreased below 75% $${F}_{wc}$$ water stress indicating reduced nutrient uptake and transport, which severely affect growth and tolerance. The results highlight compensatory physiological and biochemical responses under mild stress (75% $${F}_{wc}$$ ), which can increase the vulnerability of plants in drought-prone environments.