Application of lonizing Radiation as a Tool for Embryological Studies in Brassica. : I. Effects of Gamma Radiation on Cell Division and Growth of Embryos and Endosperms in B. pekinensis RUPR. irradiated at Different Stages of Embryo Development

Abstract

Effects of radiation on the embryonic development of Brassica pekinensis were inves-tigated quarititatively in relation to sizes of embryo, cell number of embryo and endosperm, mean cell size and difference between embryo and endosperm after irradiation. Embryos at different embryonic stages ranging from zygotes to small globular embryos were irradiated with 10 and 20KR of gamma rays for one day (Fig. 2). Pods were sampled for the observation of histological development of embryonic tissues. i. e., sizes of embryo, cell number of embryos and number of endosperm nuclei (apical and basal endosperm nuclei). A central size of continuous paraffin sections was selected as a part for measuring each tissue. The size of embryo expressed with transverse and longitudinal diameters of embryo tended to decrease when the plant was irradiated at more advanced stages. Cell number of embryos and the number of endosperm nuclei were seriously decreased by irradiation through entire stages tested, i, e. zygote through small globular at 6 days after irradia-tion.