Abstract:When sorghum seedlings were rapidly shifted from the cultural temperature of 30℃ to 40℃ and 45℃, a set of abnormal proteins, generally referred to as heat shock proteins were induced. They are a group of high molecular weight proteins (about 66–117 kD), a few intermediate molecular weight proteins (33–66kD) and a low molecular weight protein of 18 kD. At the same time, the synthesis of normal proteins was relatively depressed. The res ponse of the shoot tissues of sorghum seedings to heat shock is similar to that of the root tissues, but there are some differences in more detail between the two tissues. The synthesis of heat shock proteins in sorghum seedlings was rapid. After one-hour exposure at 45℃ their synthesis in the roots was detectable. Maximum induction took place in the second hour of exposure, thereafter their synthesis began to decline markedly. Finally, there appear to be some proteins whose synthesis was not supressed during heat shock, It is not yet known why the synthesis of these proteins is so stable.