Studies on the Developmental Physiology of the Cortical Disintegration in Rice Roots

[摘要] In the previous paper, one of writers has suggested that the physiological significance of cortical disintegration in rice roots might be the energy supply to the elongation of the root axis and the lateral root growth. These experiments, using the rice seedlings from 1 to 14 days after bedding were carried out to throw light on the relations among the nitrogen and phosphorus metabolism, the growth of various seedling organs and the cortical disintegration in seminal roots. In 3 days after bedding, the adventitious and lateral roots emerged on the seedling axis. Length of seminal root elongation per day, and initiation and developement of lateral roots were most vigorous in this stage. Increase of the total nitrogen and phosphorous contents in seminal roots carne to the saturation level in 6 and 4 days after bedding respectively. But, after that the elongation of the seminal root went on for 10 days to attain about 50 to 60% of the total langth. This result indicates that the elongation of the seminal roots depend upon the nitrogen and phosphorus derived from aged tissues, after supply of the same to seminal root ceased. While the increase of total nitrogen and phosphorus contents of seminal root cylinder (seminal root cutting off lateral roots) took 3 days after bedding to be saturated and began to decrease later on. These results indicate that the nitrogen and phosphorus contents of the root cylinder might have moved to the lateral roots. The formation of lacunae began 2 days after bedding and developed rapidly till 6 days after bedding. The initiation and developement of lateral roots, closely related to the lacunae emergence and developement, proceeded to keep pace with them. On the other hand, soluble fraction of nitrogen and phosphorus compounds changed remarkably from 1 to 4 days after bedding. SPN meant the cytoplasmic protein nitrogen increased from 1 to 3 days after bedding. Nevertheless the maximum growth rate was found at 3 days after bedding, the increasing rate of SPN at 1 to 2 days was higher than 2 to 3 days after bedding. As the process of the cortical disintegration can be regarded as the catabolic process of cytoplasmic protein, the synthetic process of cytoplasmic protein is superior than that of catabolic one for 1 to 2 days after bedding; both processes are in equibrium for 2 to 3 days after bedding and after that the catabolic one is dominant. In 4 days after bedding, SP containg P compounds decreased, whereas the inorganic phosphorus increased. Generally speaking the decrease of ∼P level shows that in the metabolic pattern synthetic charactor is converted into the catabolic and in the functional pattern, the developmental one into the preservative. This result indicates that these changes of metabolic pattern take place in seminal root at 4 days after bedding. The collective estimation of the physiological significance of the cortical disintegration by these results is tiat this physiological role may be the system of energy supply to elongation of the root axis and lateral root developement. The stage of the changes of the metabolic pattern in seminal root agrees with that of begining of adventitions root growth.

[学科分类] 农业科学（综合）