Abstract: The heading behaviour of 3 spring wheat cv, and their difference in photoperiod sensitivity were subjected to an examination in this study. By means of the vertical poly1acrylamide gels electrophoresis the developmenetal changes of the esterase, α-amylase isozymes in a successive series of young leaves newly expanded were studied under anatural growth-condition of winter, a higher temperature of autumn and different photoperiod treatments. The results showed that the electrophoretic patterns of the twoisozyme systems varied with plant growth-ages, and all may develop certain intense enzyme bands at the 5th or 2nd leaf stage. Under the natural growth-condition of winter the 3 wheat cv. have a similar mature periods, and their zymogram patterns at 5th leaf stage appear to be the same. But at the higher temperature of autumn the intervarietal difference in the types of photoperiod sensitivity were displayed, and the isozyme phenotypes at the 5th leaf stage exhibited a corresponding variation: for the two lower sensitive wheatcv. under LD (cont. illum.) treatments some characteristic enzyme bands appear at 5th leaf stage, whereas for the higher sensitive wheat cv. under LD treatments the similar enzyme bands may develop a very high intensityat 2nd leaf stage, or at 5th leaf stage under SD (8hr)treatments.