This study aimed to evaluate the physiological performance of 13 promising advanced lines and the cultivar Namangan-77 of upland cotton (Gossypium hirsutum L.) under different water supply conditions. Genotypes enunciated significant differences for plastid pigments under optimal and water-stressed conditions. The results revealed that a marked decrease in pigment content expressed impaired photosynthesis, weakened leaf energetic status, and increased metabolic disruptions in drought-sensitive genotypes, whereas pigment retention reflected robust adaptive mechanisms in drought-tolerant cotton genotypes. These physiological mechanisms confirmed that pigments served as reliable biomarkers for assessing drought-tolerant cotton genotypes. The results exhibited water deficit conditions significantly affect key processes in cotton plant leaves, from water balance to the stability of the photosynthetic apparatus. Under optimal conditions, all physiological processes proceeded efficiently, while under modeled drought, it activated complex adaptive mechanisms to preserve more water and pigments, reduce transpiration, and stabilize the leaf structure.

Keywords: Upland cotton (G. hirsutum L.), water regimes, drought stress conditions, physiological traits, chlorophyll, carotenoids, morphological traits, agronomic variables

Key findings: The plastid pigments’ analysis showed drought-tolerant cotton (G. hirsutum L.) genotypes (T-217, T-4, and Xi Zhong 52) retained higher pigment levels under water stress, while drought-sensitive genotypes (Namangan-77, T-2, and Xi Zhong 78) exhibited a significant decrease in pigment content. The results highlighted the effectiveness of using a comprehensive assessment of physiological, morphological, and agronomic traits to select drought-tolerant cotton genotypes.