Abstract
The present writers made studies on the following matters for four years from 1956 to 1959 applying the field and pot tests in the University of Fukui (Fukui City) and Tatetsu Branch Station of Osaka Prefectural Agricultural Experimental Station (Kawachi City). We studied how the thickness of bran layer is influenced by (1) the conditions of fertilization, (2) the position of spikelet and the size of rice kernel, (3) stage in ripening process, (4) transplanting time, (5) shading of the sunlight and changing air temperature. We also measured how thick the bran layer was and studied the characteristics of its forms. Our results were a s follows: I Bran layer becomes thicker according to the different amounts of fertilizer given, namely, none, standard, or plenty; and nitrogen fertilizer proved to be most effective. The same tendency may be observed when we use base or additional fertilizer, or foliage sprays after flowering. II We noticed a considerable difference between Fukui yields and Osaka ones. Regardless of the varieties of rice or conditions of applying fertilizer, Fukui yields were always thicker. It may be conjectured that it was caused by the difference of meteorological conditions, especially that of air temperature. III A difference of the thickness of bran layer was not observed according to the position of spikelet and the width of rice grain, but the thicker grain had comparatively a thicker bran layer. IV In measuring how thick the bran layer was, we compared the materials every five days from the fifteenth day after flowering and continued our observation until the ripening time. The thickness of bran layer 15 days after flowering amounted to 80∼98 % of that of ripe one and Fukui yields grew thicker than Osaka ones. From this fact we can conjecture that the thickness of bran layer will be influenced by climatic conditions, especially air temperature during the 15 days after flowering. V One plot was transplanted at the standard time and two transplanting were caried out prior to this, while four others were done later. Every transplanting were done at a regular interval of 15 days. Then we measured thickness of bran layer and found respective significant correlations between the thickness of bran layers of the dorsal part and the average air temperatures in a day, in the daytime, and at night, and the average daily duration of sunshine for the two periods extending over 10 days and 15 days respectively after flowering. VI After shading of the sun light, and low temperature treatment we confirmed that both thse factors are harmful to the thickening of aleuron layer. VII By the morphological observation of the thickening stage of bran layers and the vascular bundles, it is possible to classify the seed formation into six types as shown in Fig. 1.
