CUMULATIVE RADIATION EFFECTS ON SEXUAL REPRODUCTION IN PINE AND OAK

Trees in a natural pitch pine-oak forest have been exposed to varying amounts of low-level chronic gamma radiation for several years. Responses range from lethality to minute morphological changes, depending upon dose rate and species. The cumulative effects of low-level chronic gamma radiation on male and female flowers. pollen production. pollen germination and development of seedlings from seeds of irridiated mother trees are described. (C.H.

PROGENY TEST FROM A PITCH PINE-OAK FOREST, DAMAGED BY LOW LEVEL CHRONIC GAMMA RADIATION

A forest of Pinus rigida and Quercus sp. surrounding a Co/sup 60/ radiation field were exposed to about 2 to 4.5 r/20 hr day for the pine trees and 3 to 6 r/day for the oak trees during 1960 and 1961. The trees had been subjected to varying radiation doses since l95l. Seeds from cones collected from the pine trees and acorns from the oak trees were planted. Seeds that had matured during 1958. 1959. 1960. and 1961 were available from some-pine trees. All the acorns were formed during 196l. A significant decrease was noted in the germination of seeds from irradiated pine trees. This decrease in germination of the irradiated seed was associated with the total dose to which individual female parent trees were exposed prior to and during seed formation. There was a significant decrease in survival and rate of growth of oak seedlings from acorns of irradiated trees when compared with controls. The pines were observed to be much more sensitive to radiation than the oaks. Results indicate that a pitch pine forest severely damaged or killed by low-level chronic radiation could regenerate itself once radiation had ceased from seed stored in serotinous cones. Oak regeneration from seed would be dependent upon the timing of exposure in relation to the current flower and seed crop. (C.H.