Answer to Question #1280 Submitted to "Ask the Experts"

Q

What are the effects of radiation on a bean seed during germination?

A

The term "radiation" covers a wide variety of types of energy, from the nonionizing radiations to the ionizing radiations. All the forms of radiation may have some effects on plants or seeds, good and bad. To answer your question thoroughly, we would need more information—like what type of radiation and how much. Nonionizing radiations include microwaves (heating effects), visible light, and UV (sunburn), not to mention the lower-energy forms like radiowaves. The ionizing radiations include x rays, gamma rays, beta and alpha particles, and neutrons.

All seeds are exposed to natural radiation, as is everything in the world. So, a small amount of radiation would have no effect on the seeds or plants. The higher the dose (amount of radiation), the more of an effect you would expect. Ionizing radiation at high levels can cause inhibited sprouting and slow seedling growth and with increasing dose, reduced plant fertility and induced chromosome aberrations. But, these effects are only seen at very high doses.

The Food and Drug Administration has approved irradiation of seeds for sprouting (like alfalfa sprouts) with doses up to 8 kGy (21 CFR 179 U.S. Nuclear Regulatory Commission). Doses this high can kill microorganisms (pathogens like E. coli) on the sprouts without affecting the seeds or sprouts appreciably. This should reduce some cases of food poisoning that occur from eating the raw sprouts each year.

Research has been going on for a number of years with ionizing radiation and plants, due to the space program. Will seeds survive and be able to grow if sent on space missions? How much shielding is needed to protect them? Questions like these are what scientists, both in the United States and Russia, have been studying for years.  A resource for you to look at is The Effects of Over Exposure to Ultraviolet Radiation on the Growth of Plants and Bacteria.

Bruce Busby, CHP