Different crop management practices significantly alter agronomic and physiological traits of cotton. Excessive vegetative growth results in low seed cotton yield as reproductive growth is suppressed. Mepiquat chloride (MC) is a plant growth regulator capable of suppressing vegetative growth and enhancing reproductive growth of cotton. Optimum plant spacing improves planting density and physiological attributes of crop plants. The current study was laid out according to split-plot arrangement with three replications at research area of Department of Agronomy, University of Agriculture Faisalabad. Treatments comprised of two factors, i.e., five levels of MC (0, 30, 60, 90, 120 g ha^-1) and two plant spacings (23 cm and 30 cm). Effect of plant spacing was non-significant for most of the studied agronomic, physiological and quality characters of cotton. Likewise, its interaction with MC was also non-significant except for seed cotton yield and ginning out turn. Application of MC helped the cotton plants to achieve optimal plant height which was reduced by 3 to 13%. Application of 90 and 120 g ha^-1 MC resulted in statistically similar plant height. Increments of 35 and 46% in sympodial branches were recorded in response to 90 and 120 g ha^-1 MC, respectively. Upper limit of seed cotton yield was noticed under wider plant spacing of 30 cm and application of 120 g ha^-1 MC. Among physiological characters’ nitrogen contents, chlorophyll a and b contents and relative water contents were increased by increasing MC levels regardless of plant spacing. Fiber quality traits also responded positively to MC application. The application of 120 g ha^-1 proved optimum level of MC for better growth and yield of cotton plants.

Keywords: Crop Stature, Canopy Architecture, Gossypium hirsutum; Mepiquat chloride; Plant spacing; Fiber Quality