AbstractThe effect of seedling pretreatment at different temperature levels and periods of exposure on growth, pigments, carbohydrates and proteins was studied in three grain crops; sorghum, wheat and barley at different stages of growth. Greater shoot‐dry weights were obtained in sorghum with exposure for 15 hrs at 40 °C in the flowering, in wheat for 2 hrs at 10 and 40 °C in the fruiting and in barley for 15 hrs at 0 °C in the flowering stage. Increased root‐dry weights were achieved by wheat with exposure for 4 and 15 hrs at all levels even at 0 °C in the flowering and for 15 hrs at 40 °C in the fruiting stage. Chlaand Chlbwere more responsive in sorghum to higher temperature pretreatments than either wheat or barley. In sorghum the temperature extremes (0 and 50 °C) had resulted in a substantial reduction of Chla, and Chlbin the fruiting stage. Lower and higher temperature‐pretreatments had resulted in total available carbohydrate reduction in shoot and root of sorghum and wheat at the early stage, but the reverse was true later in flowering. In contrast, lower and higher temperature pretreatments had increased shoot‐protein in sorghum and wheat in the vegetative and in sorghum in the flowering stage. Root‐protein was more responsive to low temperature‐pretreatments in sorghum and barley during t
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