Aims Manganese (Mn) is toxic to plants at high concentrations with recent evidence indicating slowed tropical-tree growth by high soil Mn concentrations. However, little information exists about the physiological effects of high Mn on tropical trees. We investigated physiological responses and toxicity effects of Mn in several tropical tree species. Given potential physiological interactions between Mn and phosphorus (P), we also hypothesised that P could be used to detoxify Mn. Methods We conducted two controlled-growth experiments on seedlings of five tree species from Panama. The first experiment tested the effects of increasing concentrations of soil Mn; the second examined whether P availability mitigates Mn toxicity. Results Severe Mn toxicity occurred at 5 mM Mn, with toxicity symptoms in some species at 1.5 mM Mn. Responses to Mn toxicity were species-specific and depended on P supply. One species intolerant of high Mn responded by using P for detoxification; others either tolerated or detoxified Mn by another mechanism. Conclusions We conclude that Mn can be toxic to tropical tree species and Mn toxicity increases P demand in some species. Other species are broadly tolerant of high Mn, suggesting that Mn tolerance might contribute to differences in species distributions and growth of tropical trees.

中文翻译：

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土壤锰对热带树木的毒害作用

目的 锰 (Mn) 浓度高时对植物有毒，最近的证据表明土壤中锰浓度高会减缓热带树木的生长。然而，关于高锰对热带树木的生理影响的信息很少。我们研究了锰在几种热带树种中的生理反应和毒性作用。鉴于 Mn 和磷 (P) 之间潜在的生理相互作用，我们还假设 P 可用于解毒 Mn。方法 我们对来自巴拿马的五种树种的幼苗进行了两次控制生长试验。第一个实验测试了增加土壤锰浓度的影响；第二个检查 P 可用性是否减轻 Mn 毒性。结果 在 5 mM Mn 时出现严重的 Mn 毒性，在 1.5 mM Mn 时某些物种出现毒性症状。对锰毒性的反应是物种特异性的，取决于磷的供应。一种不耐受高锰的物种通过使用磷来解毒；其他人通过另一种机制耐受或解毒锰。结论 我们得出结论，锰可能对热带树种有毒，锰毒性会增加某些树种的磷需求。其他物种广泛耐受高锰，这表明锰耐受可能导致物种分布和热带树木生长的差异。