The Effects of Gamma Radiation on Plants
Gamma rays are a high-energy form of electromagnetic radiation.
Gamma rays are photons of electromagnetic radiation emitted from unstable nuclei like those formed during nuclear fission. Their wavelengths are typically less than 10 ^ -12 meters, and their frequencies usually exceed 10 ^ 20 Hertz; consequently, they have sufficient energy to eject electrons from atoms and cause damage to tissues in living organisms. At high doses, gamma rays can harm plant life.
If doses are high enough, irradiation with gamma rays may be sufficient to kill most or even all of the plant species in a community. An Oak Ridge National Laboratory paper in 1995, for example, cited previous work studying past radiation releases in the Soviet Union like the Chernobyl disaster. Doses of radiation exceeding 500 rads (a unit measuring radiation and equivalent to 10 milliGray) per day completely killed off plants, even those that had higher tolerance levels. Doses of 10,000 rads per year caused complete destruction of exposed ecosystems and their plant inhabitants. Some species were more sensitive than others; pine trees, for example, fell victim to doses as low as 5 to 10 rads per day according to the report.
Lower doses of radiation do not kill plants but can induce a range of abnormalities. Withered crowns, underdeveloped or misshapen leaves and unusual growth patterns such as gigantism -- excessive height and over-rapid growth -- characterize plants exposed to intermediate doses of gamma rays. When doses are sufficient to kill many of the existing plants, subsequent recovery may be slow.
Seeds exposed to high levels of radiation will not germinate. Seeds exposed to intermediate levels of radiation may actually exhibit higher growth rates at first, although the percentage of seeds that germinate decreases as the radiation dose increases. The gamma rays induce DNA damage and the higher the dose, the more damage to the plant's DNA they cause. Different plants may exhibit different tolerance levels; some seeds and seedlings can survive higher doses than others.