稲品種における胚の発育に関する形態学的研究 (予報)

抄録

In this paper the writer dealt, first, with the developmental process of the rice embryo in detail, especially with the progress of differentiation of its various parts and the change in the size and shape at different stages from twenty-four hours after the anthesis to the maturation of the ovule into a seed, and with the relation between the development of embryo and the ripening of grain, and secondly, with the varietal difference in the embryo and its comparative morphology between the rice plant and other cereals. For the comparative investigation amongst the cereals, the data in wheat, barley, rye and oats presented in the author's previous papers (SUETHUGU; 1950, 1951), were referred to. The materials used in this study were prepared from plants of 18 varieties different in the growth habit or other characteristics, belonging to either of the two subsp. "Indica" and "Japonica". The microscopical study was done by means of the usual paraffin method. In addition to them, other 32 varieties of which the embryos of dead ripened grains were sectioned by hand without fixing or staining were supplementarily for investigation of varietal differences in fully formed embryo. The results are summarized as follows : (1) In the material taken 24 hours after anthesis, the egg cell which had already been fertilized was divided into from 3 to 12 cells of the proembryo. These number of divided cells were found different for different varieties. In general, they were many in early ripening varieties, while were few in late varieties. (2) In most varieties the first sign of differentiation of the rudiment of each organ in the proembryo was noticed from 3 to 4 days after anthesis, but in one late variety it was after 5 days. (3) In most varieties, the coleoptile began to develop at that time, but in some varieties or samples, 5 days after it. (4) The rudiment of the first foliage leaf became visible about 5 or 6 days after anthesis in almost all varieties, while in the latest one variety it was seen about 7 days after anthesis. (5) In most varieties the rudiment of the second foliage leaf appeared about 6 or 7 days after anthesis, while in the latest variety it was seen about 9 days after anthesis. (6) About 4 or 5 days after anthesis, the scutellum began to develop into a scute form, and the epithelial cells of the scutellum commenced to show its own shape about 10 or 11 after anthesis; in most varieties, but in the ealier varieties it was 9 days, and in the latest one, 15 days, after anthesis. (7) The rudiment of the third foliage leaf became visible in most varieties about 11∼15 days, but in the earlist one 9 days, and in the latest about 20 days, after anthesis. (8) About 20∼25 days after anthesis, all the organs of embryo were found to differentiate completely, attaining to the forms typical in the full ripened grains. And the varietal differences were noticed in regard to the ripening times. (9) The stage of completion of morphological development of rice have been reported to be 10 or 14 days after anthesis by previous investigaters. The writer infers that the inconsistency of those results with that of this investigation may be attributed to the improper conception of the formation of the epithelial layer of scutellum or the differentiation of the primordium of third foliage leaf by most of the previous investigators. (10) It seemed that the length of the period from anthesis to the time of differentiation of each organs of the proembryo varied according chiefly to the temperature on and after the time of anthesis, viz. the early varieties required short periods, but the late ones required long periods in general. (11) The growth curves of the length and thickness of embryo fromed S-shapes in the rice plant similarly as in the other cereals, but the forms of the curvees showed certain variations according to the variety. [the rest omitted]