Histogenesis and Polysaccharides at the Early Stages of Development in Rice Kernels

Abstract

Using a glutinous, an indica and several non-glutinous varieties on rice plants, the histochemical investigation was carried out on the localization and properties of polysaccharides, except for cellulose, hemicellulose, mucilages and gums, at various stages of seed development until 7 days after flowering. Within 3 days after flowering non-starch polysaccharides localized markedly in the epidermis of nucellus, inner integument and funicles, and they have had amylose-like properties, which were indicated by α-and β-amylase treatment, PAS and I2 reactions. Three days after flowering, a large amount of polysacharides was found in the endosperm tissues evenly, in which three or four cell layers had been formed already. Their properties were just similar to the marginal tissues mentioned above. On the 4th day the embryo sac was almost filled with the endosperm cells. On and after the 4th, the polysaccharides as yet, were found distributed in the inner integument and funicles but did not be found in the epidermis of nucellus. Coincidently the wall between epidermis of nucellus and inner integument being thickened and the radial cell wall of the epidermis of nucellus being indistinct in cross sections the structure of the epidermis of nucellus developed as a pipe sourrounding the endosperm tissues. On the 5th day after flowering, the aleuron layers were differentiated from the endosperm tissues. Amylose-like, non-starch polysaccharides were strikingly detectable in this aleuron layers adjacent to the epidermis of nucellus. At that stage the starch in the pericarp began to decrease. From these results, it is assumed that the sugars necessary for starch synthesis in the endosperm are mainly translocated (1) from dorsal vascular bundles via funicles, (2) from marginal tissues centripetally, and (3) from dorsal vascular bundles via epidermis of nucellus and aleuron layers. It seems to locate through the pathways of (1) and (2) within 3 days after flowering but (1) and (3) after 4 days. With jodocium response, the starch in endosperm cells was shown liquid and pink in japonica varieties while granular and light-brown in CENTURY PATNA, (an indica variety) on the 4th day. The results on the amylase treatments and the jodocium reaction seems to indicate that the starch is amylose-like, consisted of short chains α-D glucopyranose units, and low molecular compound having of a glycogen-like structure in japonica and CENTURY PATNA varieties respectively. These starches increased number of branches and developed chains as the seed matured. The polymerization pattern of japonica varieties is illustrated in figs. 35 to 41. However such pattern can not be observed in CENTURY PATNA. It can be concluded that the distribution of phosphorous body in the endosperm tissue, which is considered to be related to starch synthesis, corresponds with starch polymerization in japoica varieties but not in CENTURY PATNA.