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| Fig. 1: Sunflower seedlings three days after germination. (Source: Wikipedia Commons) |
It is important to understand the implications radiation can have on seed survival and germination, because plants are a vital part of most sustainable ecosystems. Germination, the process by which a plant grows from a seed, is shown in Fig. 1.
Exposure to radiation has been found to cause a large range of effects on seeds. In a study done by Marcu et al. on the effects of radiation on seeds, it was found that radiation not only impacts the germination potential and actual qualities of the germinated seedlings (such as root and shoot lengths), where germination potential is the percentage of seeds that that germinated overall and the time of germination compared to when the seed was planted. [1] Furthermore, seeds were also found to have decreased photosynthetic pigment content when they were irradiated compared to those that were not irradiated. [1] Thus, it is clear that radiation not only impacts the quantity of seedlings, but also the quality of them.
From the Marcu et al. research, it is also clear that plants and seeds are much more radiation tolerant than are other living beings. For example, the smallest dose mentioned in the paper is more than 20 times what would be required to kill a vertebrate animal. [1] Even at radiation levels 200 times the dose required to kill a person, some seeds still germinated. Seeds are clearly more hearty than other animals, and likely even full grown plants.
While research has shown clearly that radiation has a large impact on both the quantity and quality of seedlings, it has also been shown that radiation impacts various seed varieties differently. [2] There has been research dedicated to determining how to increase the shelf-life of various plants and sprouts through the use of radiation. [2] Each type of produce seed and sprout has a different level of approved radiation, with the ultimate goal being the safety of the consumer. [2]
Even if seeds germinate, radiation can have long-lasting effects on the subsequent seedlings. When seeds are exposed to high levels of radiation, even if the seeds germinate, the subsequent seedlings are at high-risk of mortality. [1] In fact, when exposed to ≤ 0.5 kGy of radiation, subsequent seedlings only survived for a maximum of 10 days. [1] Because radiation can often lead to genetic mutations, seedlings are at high risk for reduced growth, seed production, and mortality at all radiation levels. [3] Continued radiation to seedlings will only continue to exacerbate these effects. [3]
Radiation not only impacts the probability of seed germination, but it also results in longer-term effects on seedlings and their ultimate rate of survival after germination. This is extremely relevant, because of the importance of plants within sustainable ecosystems. Plants are also often the key to an ecosystem reestablishing itself after a disaster and it is important to consider how radiation can impact the reestablishment of an ecosystem in terms of both quantity of plants and in quality of subsequent plants. Furthermore there has been quite a bit of research regarding the use of radiation within agriculture to manage bacteria growth. [4]
© Emily Xie. 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] D. Marcu et al., "Gamma Radiation Effects on Seed Germination, Growth and Pigment Content, and ESR Study of Induced Free Fadicals in Maize (Zea mays)," J. Biol. Phys. 39, 625 (2013).
[2] V. Komolprasert and K. Morehouse, Irradiation of Food and Packaging: Recent Developments (American Chemical Society, 2004), pp. 107-116.
[3] R. Miller, "Effects of Radiation on Plants," Physics 241, Stanford University, Winter 2015.
[4] I. Piri et al., "The Use of Gamma Irradiation in Agriculture," Afr. J. Microbiol. Res. 5, 5806 (2011).
