MadSci Network: Environment/Ecology

Re: What are the effects of ionizing radiation on plant life?

Date: Fri Mar 20 15:12:34 1998
Posted By: R. Ted Jeo, Bio Sci Tech, St. Paul, MN
Area of science: Environment/Ecology
ID: 885840486.En

Okay, Dustin,

Radiation is not a subject that I am too familiar with so I will collaborate with our post-doctoral lab person who knows more about it.

Essentially, when you are talking about ionizing radiation, you are taking about radiation that occurs below 380 nanometers (violet light) on the spectrum. This type of radiation starts with Ultraviolet (UV), then X-ray and down into Gamma rays. Basically what happens is that the radiation breaks apart atomic bonds in molecules which releases electrons and makes ions. That is why it is called ionizing radiation.

Plants are better adapted to cope with naturally occurring ionizing radiation, like UV, then people are because they contain special chemical compounds that protect against UV radiation. After all, they live in the out of doors exposed to sunlight all the time, right? But people, on the other hand, cannot cope with this radiation nearly as well, hence the increasing awareness of skin cancer. But, back to plants...

Molecules in living material (whether plant or animal) are complex and large in size. Ionizing radiation can cause changes in plants by breaking up these complex molecules. This may change the structure of the plant DNA, creating mutations or it might just kill the cell outright. The loss of a few cells has little effect on the growth of a plant. However, when massive amounts of cells are killed, the plant may become stressed and grow slower or even die. When DNA is mutated, the existing plant may not show any mutations itself but mutations may show up in its offspring. You cannot predict what ionizing radiation will do to a plant.

Mutations by radiation in plants can easily occur at certain stages. Radiation can change the reproducing portions of the parent plant causing mutations in its offspring. However, in nature, this does not occur often because pollen itself has an extremely tough exterior and contains special pigments that protect against naturally occurring radiation (UV). When people come along, however, and use very high concentrated doses of radiation, these protection mechanisms can be overcome. The next stage where a plant's DNA can be easily mutated is at the seed stage, before the plant begins to grow. And finally, a very young plant is more susceptible to radiation mutations than an older plant.

The radiation may or may not kill the plant out right. Also, the plant would not become "radioactive" unless it was physically contaminated with the source of radiation. Think about it this way. Fruits and vegetables can be irradiated to kill insect pests, but it does not contaminate the food. It is the same idea what happens when you get an X-ray taken. You do not become radioactive either.

I hope that this explains what you want to know. If not, you might want to re-submit your question to the physics category on MadSci Network.

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