ACUTE GAMMA IRRADIATION OF QUERCUS SEED--ITS EFFECT ON GERMINATION AND SEEDLING GROWTH

Dormant seed of Quercus alba and Quercus rubra were irradiated with gamma rays from Co/sup 60/ to determine the efiect on cytological and morphological expression in the resulting seedlings. Investigations included varying moisture content and physiological state of the seed prior to treatment, and preliminary evaluation of induced mutation. The following observations were made. The lethal radiation exposure was the same for both species although there were differences in germination within the treatment range of 1 to 10kr. Quercus alba showed an LD/sub 50/ of 6kr with a significant regression for radiation level. The regression of germination on radiation level was not significant for seed of Quercus rubra, but germination was suppressed at the higher levels. These species differences are thought to be due more to physiological than genetic factors. Height growth in the two species was complexed by sprouting in reaction to radiation damage of the apical primordia. Seedling height at the end of one year was not a significant measure of radiation damage. The type of sprouting obtained is discussed in relation to diplotonic selection within the irradiated embryonic primordia. Growth of the root at 10 days following inception was established as a macro-measure of genetic damage. Changes in moisture content (above 25%) or metabolic activity prior to germination did not significantly change the response of root growth to radiation exposure. It is suggested that initial root growth is useful as a bioassay of radiation effect on the seed of woody angiosperms where sprouting is comraon. The range of 1 to 10kr is recommended for use in oak seed irradiation experiments for the induction of mutations. Preliminary evidence at the end of the first growing season indicates that most aberrations observed are generally deleterious to total growth. However, many of the irradiated seedlings were as large as the controls and at least one irradiated seedling was outstanding in total growth. (auth