Cultivar variation in cotton photosynthetic performance under different temperature regimes

Abstract

Cotton (Gossypium hirsutum L.) yields are impacted by overall photosynthetic production. Factors that influence crop photosynthesis are the plants genetic makeup and the environmental conditions. This study investigated cultivar variation in photosynthesis in the field conditions under both ambient and higher temperature. Six diverse cotton cultivars were grown in the field at Stoneville, MS under both an ambient and a high temperature regime during the 2006-2008 growing seasons. Mid-season leaf net photosynthetic rates (P N) and dark-adapted chlorophyll fluorescence variable to maximal ratios (Fv/Fm) were determined on two leaves per plot. Temperature regimes did not have a significant effect on either P N or Fv/Fm. In 2006, however, there was a significant cultivar × temperature interaction for P N caused by PeeDee 3 having a lower P N under the high temperature regime. Other cultivars' P N were not affected by temperature. FM 800BR cultivar consistently had a higher P N across the years of the study. Despite demonstrating a higher leaf Fv/Fm, ST 5599BR exhibited a lower P N than the other cultivars. Although genetic variability was detected in photosynthesis and heat tolerance, the differences found were probably too small and inconsistent to be useful for a breeding program.