Abstract:Winter wheat “Nong Da 139” and spring wheat “Zhong 8022” were used for this experiment. The effect of low temperature treatment at different periods on protein content and composition of the seedling shoots as well as subsequent development was studied. The main results are as follows: 1. More than 40 days of vernalizing treatment were required for a rapid and uniform earing by winter wheat “Nong Da 139”. After 14–21 days vernalization, the winter wheat is possible to ear in summer, but in an irregular manner. The results indicate that during the whole vernalization process, the effect of low temperature on earing development varies with the duration of treatment. At the earlier stage, it is likely that the Iow temperature induces a change in physiological process, and in the later stage, it only accelerates the development. It is there- fore, suggested that there are two distinct processes existing during vernalization. The transformation from the former to the latter state appears to occur at the middle period of vernalization process. 2. The protein metabolic inhibitors, such as ethionine and p-fluorophenylalanine, interfere with the vernalizing process of winter wheat also at its middle period. 3. With low temperature treatment for different periods, the soluble protein content and composition are found to be changed in winter wheat shoots. At the middle-stage of vernalization (after 14 days low temperature treatment), not only is the content of protein increased twice as compared with the control, but new proteins (on electrophorestic gel) are also produced. On the contrary, there was no difference in protein bands for spring wheat. Spring wheat not to be treated by low temperature, has already possessed the proteins that appeared in vernalized winter wheat shoots. These results demonstrated that the days of 14–21 are the critical time for the vernalization of the winter wheat. The new proteins synthesized at this stage might be the factor of the determination whether or not the plants will transform from vegetative stage into reproductive phase.