1.The results obtained in different experiments on the period of potassium supply, indicate that the maximum of partial productive efficiency on grain yield was seen during 35 to 45 days before heading, but it of straw decreased rapidly after the middle decade of July.(See table II). 2.The influence of potassium defficiency of this period on the nutritional condition of whole plant appears at the young panicle formation stage resulting in the incomplete formation of panicles.(See table III and IV). 3.As shown in table I and III the increase of potassium content of young panicle and stem in potassium defficient plant is larger than that of boot leaf. This result points out that in low potassium level the transfer of potassium from leaves to young panilce and stem would be restricted by the strong adsorptive power(viz.activity of living protoplasm)of active leaves in the stage of young panicle formation.balance of the activity level of these organs remarkably affecting its translocation.