Unveiling flooding tolerance in eggplant (Solanum melongena L.): insights into biomass allocation, photosynthetic resilience and antioxidant defence strategies

Abstract

Background and aims: Flooding is a significant abiotic stress that negatively impacts the growth and yield of flood-sensitive crops. Unlike other Solanaceae species, eggplant (Solanum melongena L.) maintains root viability under partial submergence without forming adventitious roots. This resilience is likely due to efficient carbohydrate utilisation, anatomical adaptations such as aerenchyma formation, and robust reactive oxygen species (ROS) scavenging systems. Flood-tolerant eggplant accessions are commonly used as rootstocks to confer waterlogging resistance to other crops, such as tomato. This study aims to explore the physiological and biochemical strategies employed by flood-tolerant eggplant accessions to mitigate waterlogging stress.Methods: Four flood-tolerant eggplant rootstocks were subjected to nine days of partial submergence at the end of which biomass, biometric and photosynthetic parameters were measured, and biochemical analysis mainly focused on antioxidant activity. Results: Flooded plants showed a conserved reduction in leaf area through early abscission, which reflects a critical water-saving strategy. Notably, photosynthetic efficiency in younger leaves remained largely unimpaired, with minimal photoinhibition, suggesting preserved PSII functionality. Ascorbic acid, one of the main antioxidant compounds found in plants, increased across genotypes despite unchanged ascorbate peroxidase and glutathione reductase activity, suggesting that de novo ascorbic acid biosynthesis serves as a non-enzymatic buffer against reactive oxygen species. These findings suggest conserved adaptations, where peroxidase activity compensates for the limited engagement of ascorbate peroxidase in leaves.Conclusion:This study enhances our understanding of flood tolerance in eggplant by revealing a coordinated response that involves selective biomass reallocation, maintenance of photosynthetic capacity, and diverse antioxidant strategies.