Various characteristics of rice seedlings grown under 2 different sowing densities and growing temperature were investigated at the growth stage of 3.5 and 4.5 leaf age, and immediately after the investigation, the seedling were transfered in a batch filled with city water and water cultured 7 days in a growth cabinet and their rooting activities and the change in growth characteristics of seedlings during the 7 day period of the rooting experiment were examined. The results obtained were summaerized as follows ; 1. Leaf sheath dry weight of seedlings in the low-temprature and low-density plot were higher than those in high-temp. and high-density plot. 2. The NAR of seedlings in low-temp. and low-density plot were higher then those in high-temp. and high-density plot. 3. Close relation between root dry weight newly appeared durig the period of rooting experiment and sheath fresh weight/sheath length of seedlings was recognized and the correlation coefficient was 0.989. The substantiality of leaf sheath, therfore, seemed to be one of the indices to ascertain the quality of seedlings. 4. Percent increase in seedling dry weight during the period of rooting experiment was 12% and more than half of the increased dry matter was accumulated in the leaf sheath of seedlings. So that, it seemed that the increased dry matter during the period was not so much utilized for the growth and development of new root of the seedlings.

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