Ammonium nutrition as a strategy for cadmium mobilisation in the rhizosphere of sunflower
Ammonium nutrition as a strategy for cadmium mobilisation in the rhizosphere of sunflower
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DOI：
10.1007/s11104-007-9418-y
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发表时间：
2006-05
期刊：
影响因子：
4.9
通讯作者：
P. Zaccheo;L. Crippa;Valeria Di Muzio Pasta
中科院分区：
文献类型：
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作者：
P. Zaccheo;L. Crippa;Valeria Di Muzio Pasta
高等植物的铵营养导致根际酸化，这是由于根细胞排出质子所致。由铵喂养的植物诱导的酸化可以被利用来促进中性到碱性污染土壤中的局部金属动员，从而改善植物提取。研究了向日葵（Helianthus annuusL.）通过水培试验，研究了不同浓度外源镉对植物生长、地上部和根系生长的影响以及植物对可溶性镉的耐性。铵喂向日葵诱导强烈的酸化的解决方案，相比，硝酸盐喂向日葵，一个小的修改，在矿物质营养和不同的镉分配之间的根和芽。此外，铵营养被发现诱导一个很大的动员难溶形式的镉（CdCO 3）。盆栽试验研究了不同铵基肥料（硫酸铵，硫代硫酸铵，尿素）修改散装和根土壤pH值的能力，与硝酸钙和未施肥土壤的效果相比。此外，为了提高铵态氮在土壤中的持久性，进行了硫酸铵和硝化抑制剂DMPP的组合处理试验。土壤pH值强烈修改化肥转化所涉及的化学和生物过程。特别是，由于硝化作用，所有铵为基础的治疗表现出超过1.5 pH值单位和根土壤pH值的相对增加，作为硝酸盐吸收的结果，大量的土壤酸化。DMPP处理则表现出相反的趋势，根际土壤pH值低于非根际土壤。在另一个盆栽实验中，使用三种不同性质的土壤，在不同程度和类型的重金属污染的铵喂植物的能力，以调动重金属从非不稳定池。无论土壤中，金属浓度在芽中较高的植物喂铵（硫酸铵加DMPP处理）。我们的研究结果支持这一假设，铵营养与硝化抑制剂是一个可行的策略，以提高重金属植物提取，同时保护散装土壤酸化，大概从金属浸出。
Ammonium nutrition of higher plants results in rhizosphere acidification due to proton excretion by root cells. The acidification induced by ammonium-fed plants can be exploited to promote a localised metal mobilisation in neutral to alkaline polluted soils and therefore to improve phytoextraction. The effects of ammonium uptake by sunflower (Helianthus annuusL.) plants on the external medium pH, aerial and root growth and tolerance to soluble Cd were studied in hydroponic culture. The ammonium-fed sunflowers induced a strong acidification of the solution and, compared to the nitrate-fed sunflowers, a small modification in mineral nutrition and a different Cd partitioning between root and shoot. Moreover, ammonium nutrition was found to induce a great mobilisation of a sparingly soluble form of cadmium (CdCO3). A pot experiment studied the ability of different ammonium-based fertilisers (ammonium sulphate, ammonium thiosulphate, urea) to modify bulk and rhizo-soil pH, compared to the effect of calcium nitrate and to the unfertilised soil. Furthermore, in order to promote the persistence of ammonium in soil, a combined treatment of ammonium sulphate and DMPP, a nitrification inhibitor, was tested. Soil pH was strongly modified by chemical and biological processes involved in fertiliser transformations. In particular, due to nitrification, all ammonium-based treatments showed a bulk soil acidification of over 1.5 pH units and a relative increase in rhizo-soil pH as a consequence of nitrate uptake. The treatment with DMPP showed an opposite trend with a lower pH in rhizo-soil than in bulk soil. The ability of ammonium-fed plants to mobilise heavy metals from the non-labile pool was studied in another pot experiment using three soils with different properties and at different degree and type of heavy metal contamination. Whatever the soil, the metal concentrations in shoots were higher in plants fed with ammonium (ammonium sulphate plus DMPP treatment). Our results support the hypothesis that ammonium nutrition with nitrification inhibitors is a viable strategy to improve heavy metals phytoextraction while protecting bulk soil from acidification and presumably from metal leaching.