S.N. Banerjee: <i>Pinus resinosa</i>の発育中の

Abstract

Ovules ofPinus resinosafrom 1 and 2 year-old cones were collected periodically during July to August in 1963 and 1964. The embryo-gametophyte complex containing embryos at different stages of development were irradiated by a 60Co source with doses from 0.25 to 2 kilorads. The effects of radiation on the embryo and the gametophytes were determined on the basis of abnormal differentiation and abortion of embryos and the cytological anomaly in the gametophytic cells. There was less abnormal differentiation in the embryos irradiated at stage I in comparison to other stages whereas the percentage of aborted embryos was a maximum in stage I. A possible explanation of the varying radiation effect was attempted on the basis of the average nuclear volume of embryonic cells at each stage of development. In stage I, the average nuclear volume was increased about 11 to 14-fold over those in the other stages with a concomitant peak in the percentage of aborted embryos. In contrast, higher radiation effect in root apices than that in the shoot apices could not be explained through a difference in nuclear volume. The changes in the average nuclear volume in the embryonic cells at various stages of differentiation could not be explained on the basis of an increase in the DNA content alone.