Accumulation of heat shock proteins in field-grown cotton.

Cotton (Gossypium hirsutum L.) plants grown under field water deficits exhibited an 80 to 85% reduction in leaf area index, plant height, and dry matter accumulation compared with irrigated controls. Midday photosynthetic rates of dryland plants decreased 2-fold, and canopy temperatures increased to 40 degrees C at 80 days after planting compared with canopy temperatures of 30 degrees C for irrigated plants. Leaves from dryland plants which had exhibited canopy temperatures of 40 degrees C for several weeks accumulated stainable levels of polypeptides with apparent molecular weights of 100, 94, 89, 75, 60, 58, 37, and 21 kilodaltons. These polypeptides did not accumulate in leaves from irrigated plants.Addition of [(35)S]methionine to leaves of growth chamber-grown cotton plants and subsequent incubation at 40 degrees C for 3 hours radiolabeled polypeptides with molecular weights similar to those that accumulate in dryland cotton leaves. These data suggest that the proteins which accumulate in water-stressed cotton leaves at elevated temperatures (40 degrees C) are heat shock proteins and that these proteins can accumulate to substantial levels in field-stressed plants.