Physiological and molecular adjustment of cotton to waterlogging at peak-flowering in relation to growth and yield

Abstract

In the Yangtze and Yellow River Valleys of China, cotton usually suffers from waterlogging stress at peak flowering. The effects of waterlogging stress on cotton growth and yield are well documented, but little is known of its effects on the biomass allocation to reproductive parts and what determines waterlogging tolerance at physiological and molecular levels. Cotton was grown in a rain-shelter and subjected to a 10 day-waterlogging period to monitor plant growth and yield as well as physiology and expression of genes responsive for waterlogging tolerance. Plant growth and development as indicated by leaf area, plant biomass, biological yield and lint yield were significantly reduced by waterlogging stress. Averaged across the three years of study, the reductions were 26.3, 15.5, 19.8 and 26.1%, respectively. Boll weight and the number of bolls were also significantly reduced by waterlogging stress. The reduced lint yield was ascribed to the decreased boll weight and the number of bolls, as well as reduced plant dry matter accumulation and harvest index. Waterlogging reduced plant photosynthetic (Pn) rate by 16.9% and NO concentration by 17.5% but increased malondialdehyde (MDA) accumulation by 22.2%. The reduced photosynthetic performance was likely due to cell membrane damage resulting from H2O2 accumulation under hypoxic conditions. Waterlogging stress significantly regulated the expression of a set of genes associated with leaf photosynthesis, ROS scavenging, anaerobic metabolism or cell growth like LHCB, CSD, ACS6, ADH, PDC, ERFs, XTHs and EXPAs, which was the likely mechanism of cotton adaptability to waterlogging stress.