The present analysis was conducted to clarify the diagnostic characters of growth phase in the young seedling culture of paddy rice compared with the mature seedling culture of paddy rice, using the data obtained from 1975 to 1982 under the same field husbandry condition at Tottori Agricultural Experiment Station. The results are summarized as follows : 1) The vegetative-lag phase, the period from maximum tillering stage to the panicle formation stage was the most characteristic growth phase in either culture method. The period in young seedling cultures was longer than the one in mature seedling cultures. It was recognized that the vegetative-lag phase was more longer under the condition of early-planting culture with young seedlings. 2) The variation of vegetative-lag phase was controlled by the period from transplanting to the maximum tillering stage. It was estimated that the period from transplanting to maximum tillering stage was affected principally by the leaf emergence rate. 3) The panicle number per m^2 in young seedling culture was more ensured than in mature seedling culture, however, the grain number per m^2 in young seedling culture was not necessarily increased compared with mature seedling cultures because of the decrease in grain number per panicle.
