Accumulation of Heat Shock Proteins in Field-Grown Cotton

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Abstract
Cotton (G. hirsutum L.) plants grown under field water deficits exhibited an 80-85% 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.degree. C at 80 days after planting compared with canopy temperatures of 30.degree. C for irrigated plants. Leaves from dryland plants which had exhibited canopy temperatures of 40.degree. C for several weeks accumulated stainable levels of polypeptides with apparent MW of 100, 94, 89, 75, 60, 58, 37 and 21 kilodaltons. These polypeptides did not accumulate in leaves from irrigated plants. Addition of [35S]methionine to leaves of growth chamber-grown cotton plants and subsequent incubation at 40.degree. C for 3 h radiolabeled polypeptides with MW similar to those that accumulate in dryland cotton leaves. The proteins which accumulate in water-stressed cotton leaves at elevated temperatures (40.degree. C) are heat shock proteins; these proteins can accumulate to substantial levels in field-stressed plants.