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| Fig. 1: Picture of the growing forest in the Chernobyl Exclusion Zone. (Source: Wikimedia Commons) |
Given the well-documented lethality of nuclear radiation exposure to humans and animals, radiation has become associated with the sights of inhospitable wastelands, places where no life could hope to survive. Despite this common portrayal, images of some of the greatest nuclear disasters in history, such as Chernobyl in Fig. 1, tell a different story. Although devoid of human life, another type of life appears to be flourishing despite the continual radiation: plant life. This paper seeks to explain how flora is able to survive in radioactive environments and what effects the radiation may have created.
Before analyzing the effect of radiation on plants, it is necessary to first understand why radiation is dangerous to humans and animals. In addition to the burns and nausea that result from high levels of exposure, high-energy radiation is able to corrupt cells at a genetic level, which can cause the cell to die or spread the corruption as a cancer. [1] Unlike animals, however, plants are generally resistant to deadly cancers. The resistance arises from their cellular walls, which prevents cancerous cells from spreading, and their adaptive growth, which allows plants to work around damaged cells and regenerate new cells. [2] Some plants are therefore able to survive X-ray doses up to 10 Grays without significant detriment despite that same dosage being deadly for humans. [3]
Although plants are able to survive cancerous growth caused by radiation, they are still at risk of death during initial exposure. This may be seen, for example, in the pine trees closest to the Chernobyl reactor, where high exposure to radiation resulted in radiation poisoning that caused the trees pines to turn red and eventually die. [4] Due to the presence of radiation preventing microbial decomposition, the nutrients of such plants are often unable to re-enter the soil, resulting in the slow regrowth of newer trees. [5]
The adaptivity of plants allows flora to survive in radioactive environments, but survival in these radioactive areas often leads to changes in the plant itself. Some plants, such as soybeans, were found to have reduced water uptake and yield smaller fruits when grown in radioactive areas. Soil radioactivity of 7.3 × 106 Bq m-2 resulted in soybeans weighing 100 milligrams, or almost fifty percent, less than their counterparts grown in a non-radioactive environment. [6] Many plants were also found to develop defensive mechanisms that prevent dispersed radionuclides from being transferred to the plant's seeds, allowing these radionuclides to instead build up in other locations of the plant, such as the leaves and stem. [6]
Plants are able to survive nuclear disasters due to their adaptiveness in replacing cancerous cells, but they are still vulnerable to irreversible damage at high enough exposures. For plants that do adapt, survival is often accompanied with irregular growth and development of defensive mechanisms in an effort to protect both the plant and its seeds.
© Fletcher Newell. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] J. Doonan and T. Hung, "Why Don't Plants Get Cancer?" Nature 380, 481 (1996).
[2] S. Thompson, "How Plants Reclaimed Chernobyl's Poisoned Land," BBC, 1 Jul 19.
[3] C. Arena, et al, "Space Radiation Effects on Plant and Mammalian Cells," Acta Astronautica 104, 419 (2014).
[4] N. A. Beresford, E. M. Scott, and D. Copplestone, "Field Effects Studies in the Chernobyl Exclusion Zone: Lessons to be Learnt," J. Environ. Radioact. 21, 105893 (2020).
[5] R. Nuwer, "Forests Around Chernobyl Aren't Decaying Properly," Smithsonian Magazine, 14 Mar 14.
[6] M. Danchenko, et al, "Proteomic Analysis of Mature Soybean Seeds from the Chernobyl Area Suggests Plant Adaptation to the Contaminated Environment," J. Proteome Res. 8, 2915 (2009).
