Analyses on the Growth of Embryo in Some Gramineae

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Embryo growth in rice, wheat and barley was analyzed in detail. Embryo length increases very slowly at the begging stage and begins to grow exponentially when the embryo consists of 100-200 cells. Cell nurnber increases exponentially freurl the beginning but the rate of Increase falls when the embryo consrsts of 20-40 cells. Thus, the globular stage of embryo may be divided into three periods: the early period from fertilization to 20-40 cells; the middle period -frorn 20-40 cells to 100-200 cells; the late period from 100-200 cells to "two point projection" (the frst morpho-logical change from a globular embryo). Starts of the exponential growth and two growth rate rhythms at the 100-200 cell suggest that embryo metabolism is activated and cells begin to interact actively at this stage. By analyzing allometric growth between the length and thickness, we discovered that the coefficient of allometry changes a little before "two point projection" and at the late development stage, in rice and wheat. The ratio of thickness to length changes correspondingly to the change of the cofficient of allometry, both of which vary more wldely at the globular stage than after "two pomt proJectron". This indicates that the form of embryo varies greatly and is unstable at the globular stage. These results apply to rice, wheat and barley and, suggest that embryos share a ccunmon developing mechanism at least in Gramineae.
日本育種学会の論文