Caplin Nicol, Willey Neil
Centre for Research in Biosciences, University of the West of England, Bristol, Bristol, United Kingdom.
Front Plant Sci. 2018 Jun 26;9:847. doi: 10.3389/fpls.2018.00847. eCollection 2018.
Understanding the effects of ionizing radiation (IR) on plants is important for environmental protection, for agriculture and horticulture, and for space science but plants have significant biological differences to the animals from which much relevant knowledge is derived. The effects of IR on plants are understood best at acute high doses because there have been; (a) controlled experiments in the field using point sources, (b) field studies in the immediate aftermath of nuclear accidents, and (c) controlled laboratory experiments. A compilation of studies of the effects of IR on plants reveals that although there are numerous field studies of the effects of chronic low doses on plants, there are few controlled experiments that used chronic low doses. Using the Bradford-Hill criteria widely used in epidemiological studies we suggest that a new phase of chronic low-level radiation research on plants is desirable if its effects are to be properly elucidated. We emphasize the plant biological contexts that should direct such research. We review previously reported effects from the molecular to community level and, using a plant stress biology context, discuss a variety of acute high- and chronic low-dose data against Derived Consideration Reference Levels (DCRLs) used for environmental protection. We suggest that chronic low-level IR can sometimes have effects at the molecular and cytogenetic level at DCRL dose rates (and perhaps below) but that there are unlikely to be environmentally significant effects at higher levels of biological organization. We conclude that, although current data meets only some of the Bradford-Hill criteria, current DCRLs for plants are very likely to be appropriate at biological scales relevant to environmental protection (and for which they were intended) but that research designed with an appropriate biological context and with more of the Bradford-Hill criteria in mind would strengthen this assertion. We note that the effects of IR have been investigated on only a small proportion of plant species and that research with a wider range of species might improve not only the understanding of the biological effects of radiation but also that of the response of plants to environmental stress.
了解电离辐射（IR）对植物的影响对于环境保护、农业和园艺以及空间科学都很重要，但植物与从中获取许多相关知识的动物在生物学上存在显著差异。由于存在以下情况，人们对IR在急性高剂量下对植物的影响了解得最为透彻：（a）在野外使用点源进行的对照实验；（b）核事故后立即进行的实地研究；以及（c）对照实验室实验。对IR对植物影响的研究汇编表明，虽然有大量关于慢性低剂量对植物影响的实地研究，但使用慢性低剂量的对照实验却很少。我们建议，如果要正确阐明慢性低水平辐射对植物的影响，就需要开展植物慢性低水平辐射研究的新阶段。我们强调了应指导此类研究的植物生物学背景。我们回顾了先前报道的从分子水平到群落水平的影响，并利用植物应激生物学背景，针对用于环境保护的推导考虑参考水平（DCRLs），讨论了各种急性高剂量和慢性低剂量数据。我们认为，慢性低水平IR有时可能在DCRL剂量率（或许更低）下对分子和细胞遗传学水平产生影响，但在更高的生物组织水平上不太可能产生具有环境意义的影响。我们得出结论，尽管目前的数据仅满足布拉德福德-希尔标准的一部分，但目前针对植物的DCRLs在与环境保护相关的生物尺度上（以及它们所针对的尺度）很可能是合适的，但考虑到适当的生物学背景并牢记更多布拉德福德-希尔标准进行的研究将加强这一论断。我们注意到，仅对一小部分植物物种研究了IR的影响，对更广泛物种的研究不仅可能增进对辐射生物学效应的理解，还可能增进对植物对环境应激反应的理解。
