Differential response of growth and photosynthesis in diverse cotton genotypes under hypoxia stress

The objectives of the present study were to compare the dynamic of the growth and photosynthetic characteristics of cotton varieties contrasting in waterlogging (WL) tolerance when subjected to hypoxia stress. The growth of the WL-sensitive genotypes was notably inhibited by WL, mainly as a result of a significant reduction in the net photosynthesis (PN) after two days of hypoxia treatment; in the tolerant varieties, no significant changes in PN were observed until 8 d after hypoxia onset. The intercellular CO2 concentration and maximal photochemical efficiency of PSII significantly declined, and the nonphotochemical quenching increased in the sensitive varieties. Infrared thermography showed that a low stomatal conductance resulted in an increased leaf temperature under hypoxia stress. Spectral image analysis suggested that the pigment content and water content rapidly decreased in the leaves of the sensitive varieties. It is concluded that maintaining stomatal opening through the interaction of ethylene and abscisic acid may be an important strategy to improve waterlogging tolerance in cotton.