Physiological evaluation of cotton genotypes (Gossypium hirsutum L.) Under water stress conditions

Abstract

A study was conducted to determine the Leaf Temperature, transpiration rate, Stomatal diffusive resistance and photosynthetic activity of Cotton Plants under Water stress. The field studies were carried out in the Department of Cotton, Centre for Plant Breeding and Genetics, TNAU, Coimbatore. KC 2 X MCU 13-F4 population along with parents were subjected for genetic diversity analysis using physiological features. The experiment was conducted by adopting Factorial Randomized Block Design with three replications. The treatments comprised of water stress imposed at vegetative, squaring and boll development stages of crop growth. Leaf temperature was usually positively correlated with light intensity and negatively correlated with transpiration, air VPD, and soil water. Stomatal and non- stomatal factors contributes to the effects of water deficit on photosynthesis and water use efficiency Water stress may reduce leaf net photosynthetic carbon assimilation through both stomatal effects, which reduce the leaf internal CO2 concentration, and non stomatal effects, which result in reduced net photosynthetic carbon assimilation rate at a given level of leaf internal CO2 concentration. Although stomata were more numerous in the lower than the upper epidermis, most of the time a greater percentage of the upper were open. With sufficient soil water present, stomata opened with light and closed with darkness. Fewer stomata opened under low than high light intensity and under even moderate, as compared with high soil water. It required several days following re-irrigation for stomata to regain original activity levels.