Statistical Studies on Various Characteristics of Crop Plants : IX. Studies on the variations of characters among individual plants of paddy rice and two-rowed barley varieties

Abstract

It is considered that the varieties of every crop plant consist of a population of many-individuals (hills) cultured on a widespread farm under given conditions. As a result, when a variety is observed as a population of many individual plants, the individual plants comprised in a population vary widely with one another, and that the individual variations are subject to wider when they are cultured under different conditions. From such reasons, it could not be regarded as a satisfactory indicator of the characteristics of a variety to show the characteristics of each variety merely by the mean value of characters of crop plants. It would be rather a better indicator to show the variations among the characters of individuals in a population together with these mean values. From such viewpoint, the authors, in order to ftnd the first clue for observing the crop varieties as a population of individual plants, devised to use the coefficients of variation found among individual plants of characters of paddy rice and two-rowed barley varieties, as an index to the variations found among the population, and the authors examined the relationship among the estimator of tlle coefticients of variation of the individual characters and the relationship of the estimators to the planting density. The comparison of the estimators of the coefficients of variation between paddy rice and two-rowed barley plants showed that the estimators of two-rowed barley plants were always larger than those of paddy rice plants, without any exception. When viewed from the relationship of the estimators of coefficients of variation to the planting densitry, two groups of different chardcters were observed among those sample varieties: (a) the characters which bring about changes in the avelage of estimator; and (b) the characters which britig about little or no changes in the average of estimator. And it was proved that in the former case, the range of the distribution of the estimators of all the varieties changed in accordance with the changes in the average of estimator, but in the latter case, little or no changes took place in, the range of the distribution of the estimators. Regarding the effect on the estimators of coefftcients of variation caused by the planting density under review, both the average of estimator and the range of estimator distribution of all paddy rice varieties showed a tendency to become smaller according as the rate of planting density has become lower. In the case of two-rowed barley varieties, however, the average of estimator and the range of estimator distribution became smaller up to a certain extent of sparse planting, but both the average of estimator and the range of estinlator distribution tended to become larger when planted more sparsely.