Effects of gamma irradiation of Pinus banksiana Lamb. seed as expressed by M1 trees over a 10-year period

Trees grown from seed gamma-irradiated at exposures of 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14,400 and 19,200 R, and a control were evaluated for survival, growth, flowering, and cone and seed production over a 10-yr period following seed irradiation. The LD50 for seed germination was approximately 16,000 R, but that for tree survival was 12,600 R at six months, and 11,300 R after 10-yr. Shoot growth in surviving trees was significantly reduced at seed exposures as low as 7200 R during the first 2 yr and differences in tree height among exposure levels were still significant after 10 yr. Earliness of flowering and number of cones per tree were not significantly related to seed exposure. However, total seeds per cone and percent of filled seed differed significantly among exposures through at least the first 6 yr, indicating persistent radiation induced genetic changes. (author)