Comparison of the net photossynthetic rate, stomatal resistance and total yield of two cotton cultivars subjected to water stress

Abstract

This study was conducted at Instituto Agronômico do Paraná, in Londrina, PR, Brazil. Comparison was made between two cotton (Gossypium hirsutum L.) cultivars, IAC 17 and IAC 20, subjected to normal and stressed soil water availability conditions, for 25 days from the flowering onset. During this period, net photosynthetic rates (NPR) and stomatal resistance (SR) were monitored for individual leaves and, at the end, leaf water potential was also monitored. At the end of the crop cycle, yield and some yield components were compared. NPR, as well as the SR, plotted as function of photosynthetically active radiation, were fitted through the function Y = a + b* . In normal and in stressed conditions, there were not statistical differences, at 5% level, between both cultivars with respect to NPR, SR and leaf water potential. With respect to fiber length, number of boll per m² and yield, statistical differences were found only between normal and stressed conditions. Thus, it can be concluded that there was no difference in behavior between both cultivars when subjected to water stress during the studied period.