|Fig. 1: Three irradiated plants (right three).  (Source: Wikimedia Commons).|
Before I explain how radiation can affect plant-life, I must first explain what exactly radiation is, and how it is able to affect matter. Radiation comes from many places, from the Sun, to things man makes like cell phones and TV's. Radiation is not always dangerous. Radiation can become very dangerous depending on what kind of radiation it is, and how long something is exposed to it. Radiation has two types, non-ionizing, which is mostly harmless, and ionizing. This high-energy, ionizing radiation can lead to serious problems within an organism. Radiation energy is transferred by particles or waves . While non-ionizing radiation is relatively low-energy, ionizing radiation is so high in energy it can break chemical bonds. This means it can change the charge of an atom that interacts with it. At high levels, this can even damage and destroy the nucleus of an atom, directly affecting an organism's DNA. Once DNA is tampered with, an organism can develop dangerous mutations. 
The effects of high levels of radiation on organisms include: 
chromosomal aberrations, defined as visually observable changes in chromosome structure.
DNA damage, defined as any damage to DNA molecules, including DNA sequence "inversion" (TCAG now GACT) as well as sections of sequences being "deleted". 
growth reduction, defined as a reduction in the rate of growth of organisms.
reproduction effects, including sterility, reduction in reproduction rate, and occurrence of developmental abnormalities or reduction in viability of offspring.
reduced seed germination.
mortality, including both acute lethality and long-term reduction in life span.
direct burn damage to exposed tissue. 
The amount that a plant, or any organism, is affected by radiation is determined by how much radiation the organism receives, as well as long it is exposed. Data from the Chernobyl incident lends some more precise numbers. "No deleterious effects of radiation could be observed in locations where radiological doses were less than or equal to 5 rad/year. Where doses between 5 and 400 rad/year were received, radiation effects were 'ecologically masked,' meaning that adverse effects on individual organisms were observed but no changes in populations or ecosystems occurred. Where doses were >400 rad/year, damaging effects on populations and communities occurred." 
Direct contact with radiation or radioactive materials is not required to affect local plant life; the mere presence of a reactor is often enough. To build a nuclear reactor, one requires a great deal of space, usually near water, which means clearing out any local vegetation. Heat given off by the reactor can change nearby water temperature, disturbing the delicate conditions required for coastal vegetation. 
© Reed Miller. 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.
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