Shapiro, N. and A. B. Burdick
The effects of hydration on X-ray induction of mutations are being studied. Both seed and mature pollen are of special interest. Our first step with pollen was to study in vitro germination and tube growth after varying moisture and X-ray doses at room temperature. This note will present data of an experiment on line #206 of L. pimpinellifolium. Fresh pollen composited from plants grown under controlled conditions was divided into ten samples and dried over P\2\O\5 (10-12% RH) in open gelatin capsules for 24 hours. Following drying, samples were capped and irradiated. Prior to germination in a hanging drop of 25% sugar + 60 ppm boron, five of the ten samples were stored one half hour over water.
Average Average
Treatment % germ.^1 Treatment % germ.
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Control D^2 6.0 Control D-W^3 88.3
2,000r D 7.0 2,000r D-W 86.7
8,000r D 11.7 8,000r D-W 76.7
30,000r D 6.7 30,000r D-W 83.3
70,000r D <5.0 70,000r D-W 76.7
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^1 Based on 3 slides, 100 grains per slide.
^2 Dried over P\2\0\5 for one day.
^3 Dried over P\2\0\5 for one day followed by post irradiation
humidification.
Apparently dehydrated pollen, whether irradiated or not, will not germinate if
plunged directly into the germination solution; it must be air-hydrated first.
In both the D and D-W series, doses up to 70,000r did little to change
germination percentage. Previous data have indicated that samples treated
without drying, give results similar to those of the treated D-W samples.
This apparent uniformity at all levels of treatment changes somewhat when we
consider tubs growth. There are indications of variation in tube lenghts at
8,000r and an increase in short tubes at 30,000r with a further increase at
70,000r. Similar experiments when projected on a larger scale may become more
meaningful in relating radiation injury to induction of mtations.