Aquatic Ecology and Environmental Biology, Institute for Water and Wetland Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
School of Biological and Chemical Sciences, Queen Mary University, E1 4NS, London, United Kingdom.
Sci Rep. 2018 Mar 13;8(1):4451. doi: 10.1038/s41598-018-22760-5.
Azolla spp., a water fern often used for phytoremediation, is a strong phosphorus (P) accumulator due to its high growth rate and N fixing symbionts (diazotrophs). It is known that plant growth is stimulated by P, but the nature of the interactive response of both symbionts along a P gradient, and related changes in growth-limiting factors, are unclear. We determined growth, and N and P sequestration rates of Azolla filiculoides in N-free water at different P concentrations. The growth response appeared to be biphasic and highest at levels ≥10 P µmol l. Diazotrophic N sequestration increased upon P addition, and rates were three times higher at high P than at low P. At 10 µmol P l, N sequestration rates reached its maximum and A. filiculoides growth became saturated. Due to luxury consumption, P sequestration rates increased until 50 µmol P l. At higher P concentrations (≥50 µmol l), however, chlorosis occurred that seems to be caused by iron- (Fe-), and not by N-deficiency. We demonstrate that traits of the complete symbiosis in relation to P and Fe availability determine plant performance, stressing the role of nutrient stoichiometry. The results are discussed regarding Azolla's potential use in a bio-based economy.
满江红 spp. 是一种常用于植物修复的水生蕨类植物，由于其生长速度快且具有固氮共生体（固氮菌），是一种很强的磷 (P) 积累者。众所周知，植物的生长受到 P 的刺激，但在 P 梯度下，两种共生体的相互作用响应的性质以及相关的生长限制因素的变化尚不清楚。我们在不同 P 浓度的无氮水中确定了满江红 filiculoides 的生长、N 和 P 固存率。生长响应似乎呈双相性，在≥10 P µmol l 时最高。随着 P 的添加，固氮 N 固存增加，在高 P 时比在低 P 时高 3 倍。在 10 µmol P l 时，N 固存率达到最大值，满江红 filiculoides 的生长达到饱和。由于奢侈消费，P 固存率增加到 50 µmol P l 。然而，在更高的 P 浓度（≥50 µmol l）下，会发生黄化，这似乎是由铁（Fe）而不是氮缺乏引起的。我们证明了完整共生体与 P 和 Fe 可用性的关系决定了植物的表现，强调了养分化学计量的作用。结果将根据满江红在生物基经济中的潜在用途进行讨论。
