Burdick, A.B.
Seeds of autodiploid L. pimpinellifolium line 208 were exposed to thermal neutrons in the reactor at Brookhaven National Laboratory in February 1955. Part of the seeds was exposed dry (ca. 8% moisture) and another part exposed wet (soaked 24 hours at 25 deg. C then sealed in plastic bags at 3 deg. C for irradiation). Wet seeds were saturated with water and, except for the 24 hour soaking period and the period of irradiation exposure, were kept at 3 deg. C until dry again.
Three different wet pre-treatments were used 0.2% colchicine, 0.2% paradichlorobenzene, and distilled water, however most of the data were homogeneous among the three pre-treatments so the results have been grouped and reported together as a single wet treatment. One item of data mean days to germinate, did vary among the wet pre-treatments paradichlorobenzene treated seed requiring about 1.5 days longer to germinate.
The principal data from this experiment are given in table 1. Germination, survival, and sterility data are comparable for both wet and dry seeds except for the slower germination of wet-treated seeds which is entirely due to the delay, noted above, associated with the paradichlorobenzene sub-treatment.
Mutation data were taken by selfing R1 plants and observing 36-72 seedling progeny from each R1 plant for lethal and visible mutations. Lethals were expressed as a 25% reduction in germination and visibles as 25% of the progeny. Visibles were classified as "chlorotic lethals", "morphological lethals", "chlorotics", and "morphologicas". The results given in the last column of table 1, indicate a much higher mutation rate for dry-treated seed than for wet-treated seed although these differences are in no way indicated in the foregoing germination, survival, and sterility data from R1 plants. We expect to discuss elsewhere the general aspects of this apparent radiation protection by hydration. (AEC Contract AT(11-1) 335).
Table 1
EFFECT OF THERMAL NEUTRONSS ON WET AND DRY TREATED TOMATO SEED
Mean
Days %
Pre- Neutron Dose No. % to Sur-
treatment x10^13/sq.cm. Planted Germ. Germ. vival
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Dry 0 84 99 7.18 100
3.30 84 96 7.50 100
7.05 84 94 8.41 99
11.00 84 77 9.38 80
14.80 84 39 10.36 6
. . .
Wet 0 252 97 8.66 100
3.30 252 99 8.75 100
7.05 252 90 9.86 99
11.00 252 87 9.51 73
14.80 252 69 10.39 6
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No.
Tested
% for %
Plants Muta- Having
Sterile tion Mutation
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0 10 10.0
5 26 65.4
38 26 38.5
99 1 100.0
100
. . .
10 73 19.2
37 55 27.3
50 3 33.3
100
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