BACKGROUND AND AIMS UV-B radiation damages the DNA, cells, and photosynthetic apparatus of plants. Plants commonly prevent this damage by synthetizing UV-B protective compounds. Recent laboratory experiments in Arabidopsis and cucumber indicate that plants can also respond to UV-B stress with endopolyploidy. Here we test the generality of this response in natural plant populations, considering their monocentric or holocentric chromosomal structure. METHODS We measured the endopolyploidy index (flow cytometry) and the concentration of UV-B protective compounds in leaves of 12 herbaceous species (1007 individuals) from forest interiors and neighboring clearings where they were exposed to increased UV-B radiation (103 forest+clearing populations). Then we analyzed the data using phylogenetic mixed models. KEY RESULTS Concentration of UV-B protectives increased with UV-B doses estimated from hemispheric photographs of the sky above sample collection sites, but the increase was more rapid in species with monocentric chromosomes. Endopolyploidy index increased with UV-B doses and with concentrations of UV-B absorbing compounds only in species with monocentric chromosomes, while holocentric species responded negligibly. CONCLUSIONS Endopolyploidy seems to be a common response to increased UV-B in monocentric plants. Low sensitivity to UV-B in holocentric species might relate to their success in high-UV stressed habitats and corroborates the hypothesized role of holocentric chromosomes in plant terrestrialization.

中文翻译：

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内多倍体是天然植物群体对 UV-B 胁迫的常见反应，但其大小可能受染色体类型影响

背景和目的 UV-B 辐射会损害植物的 DNA、细胞和光合作用装置。植物通常通过合成 UV-B 防护化合物来防止这种损害。最近在拟南芥和黄瓜中进行的实验室实验表明，植物也可以通过内多倍体响应 UV-B 胁迫。在这里，我们考虑到自然植物种群的单中心或全中心染色体结构，测试了这种反应的普遍性。方法 我们测量了森林内部和邻近空地的 12 种草本植物（1007 个个体）的叶子中的内多倍体指数（流式细胞术）和 UV-B 保护化合物的浓度，这些草本植物在这些植物中暴露于增加的 UV-B 辐射（103 个森林+空地）人口）。然后我们使用系统发育混合模型分析数据。主要结果 UV-B 防护剂的浓度随着根据样本采集地点上方天空的半球照片估计的 UV-B 剂量而增加，但在具有单着丝粒染色体的物种中增加得更快。仅在具有单着丝粒染色体的物种中，内多倍体指数随着 UV-B 剂量和 UV-B 吸收化合物浓度的增加而增加，而全着丝粒物种的反应可以忽略不计。结论 内多倍体似乎是单中心植物对 UV-B 增加的常见反应。全着丝粒物种对 UV-B 的低敏感性可能与它们在高紫外线胁迫栖息地中的成功有关，并证实了全着丝粒染色体在植物陆化中的假设作用。