Interactive effects of high planting density and drought on physiological traits and yield in tomato

Abstract Background This study investigated the combined effects of high planting density and drought stress on morpho‐physiological traits, yield, and fruit quality in tomato plants. The research addresses knowledge gaps in plant responses to multiple concurrent stressors and explores strategies for maximizing yield per cultivation area under water scarcity conditions. Two experimental approaches were employed: a controlled environment study with 30‐day‐old tomato seedlings grown under low density (LD) or high density (HD) conditions with normal or restricted water supply, and a field experiment carried out up to the fruiting stage. Measurements included morphological traits, photosynthetic parameters, oxidative stress markers, pigment content, gene expression of shade marker genes, yield components, and fruit quality attributes. Results HD cultivation triggered typical shade avoidance syndrome responses, but unexpectedly enhanced photosynthetic rates compared to LD. HD did not exacerbate the physiological response to drought but did reduce per‐plant yield when combined with drought. Light quality modifications under HD led to increased lycopene content in fruits, suggesting potential nutritional quality benefits. Conclusions The findings challenge simplistic views of combined stress effects, revealing that moderate shade from HD cultivation may mitigate certain aspects of drought stress. While combined HD and drought reduced yield, the enhanced photosynthetic efficiency and improved fruit quality parameters suggest optimized HD cultivation could represent a viable strategy for sustainable intensification of tomato production under water‐limited environments. © 2025 Society of Chemical Industry.