Analysis on the growth pattern of glume in rice.

Abstract

Grain size is one of the important yield components and it has influences on grain yield as well as grain quality. However, it has not been well understood how grain size is determined. Certainly, glume size is one of the important factors affecting grain size. We analyzed in detail the growth of glume (floral glume) of several rice varieties differing in sizes of their glumes. 1. The growth of glume in both length (lemma length) and width (floret width) were well fitted to a logistic curve (Fig. 1). This indicates that the growth pattern of glume can be characterized by parameters estimated from the logistic curve. In every variety, the growth of the glume in length ceased earlier than that in width (Figs. 2 and 3). Thus, the growth of glume in length did not synchronize with that in width. The intervarietal differences of growth period did not correspond with those of the glume length. However, the maximum growth rate of glume in length correlated highly with the final glume length, indicating that the differences in the final glume length was due to the differences in the maximum growth rate of glume length among the variesies (Table 1, Fig. 2). on the other hand, in the glume width, we could not detect any distinct intervarietal differences in growth period or maximum growth rate (Table 2, Fig. 3). It must be noticed that the relatively wide glume of "Arborio" was caused by the prolonged growth but not by the high growth rate (Table 2). 2. The growth patterns of glume in length and in width are different and the length and width of glume may be controlled by different regulatory systems. In this point, we need to analyze the growth pattern of glume and the mechanism of determination of its size in more detail. 3. Intersecting lines comprising three straight lines could be fitted to the allometric growth between the glume length and width (Fig. 4). In every variety, the coefficient of allometry was minimum in the second section and maximum in the last (Table 3). Intervarietal differences were detected in the coefficients of allometry and the positions of intersecting points. It is clarified that the shape of glume is affected by both the ratio of growth rate in length and to that in width of glume and the time lag of the growth period in the width relative to that in the length. 4. The present results show that the size and shape of rice glume are controlled by various parameters and we cannot assign any single factor determining the size or shape of glume during its growing process.