Integrated physiological and antioxidant responses in roots and shoots underpin aluminium tolerance in sesame

Aluminium (Al 3+ ) phyto-toxicity is detrimental to crop productivity on acidic soils across tropical and subtropical climates. Sesame ( Sesamum indicum L.) is a high-valued oilseed crop of these regions, yet its physiological responses to Al 3+ toxicity is critically undefined compared to cereals, a significant bottleneck for tolerance breeding. Here, we comprehensively assessed the growth, physiological and biochemical traits of two contrasting sesame cultivars (Zhongzhi-13 and ZZM2748, representing V 1 and V 2 , respectively) under controlled Al³⁺ stress (30 mg/L aluminium sulfate) conditions. V 1 showed superior tolerance through conserving higher root length (7.4% less reduction; p ˂ 0.05), root fresh weight (25.4% decrease vs. 51% in V 2 , p ˂ 0.05), and relative water content (RWC = 71.5% vs. 56.5%). Less oxidative damage was recorded in V 1 , with electrolyte leakage (EL) and H 2 O 2 activity increasing only 1.9- and 1.6-folds, respectively, versus 3.8- and 4.4-folds in V 2 ( p ˂ 0.05 for all comparisons). Additionally, V 1 displayed a robust antioxidant defense (SOD, CAT, GR) with high accumulation of proline and soluble sugar contents ( p ˂ 0.05), whereas maintaining chlorophyll (21.7% loss vs. 39% in V 2 ; p ˂ 0.05) and preserving superior canopy architecture (canopy area, width and green ratio (GRatio); p ˂ 0.05 for CW, CA and GRatio interactions). Furthermore, genotype-specific strategy was affirmed by multivariate analysis, with V 1 traits grouped with osmoprotectants and antioxidants, while V 2 clustered with oxidative damage indicators. These observations showed a coordinated multi-component system comprising root integrity, membrane stability, osmotic regulation, and antioxidant activities in sesame for Al tolerance. This research forms one of the first comprehensive physiological report present critical insights, actionable criteria with practical and non-destructive screening tools (EL, RWC, proline and GR), and emphasize future validation across the broader range of this genotype to develop resilient cultivar for acidic regions.