The radiosensitivity of gymnosperms. I. The effect of dormancy on the response of Pinus strobus seedlings to acute gamma irradiation

Abstract

Seedlings of Pinus strobus (white pine) were exposed for 16.5 hr to Co 60 gamma radiation at dosages from 50 to 1000 r during a period of dormancy or a period of active growth. The effect on growth was determined by measurement of needle lengths. The data show the dormant plants to be considerably more resistant than the actively growing plants. Measurements of interphase nuclear volumes in apical shoot meristems made at various times during the year show a large volume during stages of active growth and much smaller volumes during dormancy. The data strongly suggest that the differences in sensitivity of dormant and actively growing plants may be largely the result of differences in nuclear volumes of these stages.