Abstract

Approximately 30% of the world’s land area is acidic soil (pH < 5.5), and aluminum (Al) toxicity and phosphorus (P) deficiency are two main constraints of plant growth in acidic soil. However, direct application of P fertilizer to acidic soil can form insoluble Al–P precipitates, thus reducing P availability. We used a split-root technique to experimentally investigate whether Eucalyptus seedlings can translocate P from root halves with no Al stress to root halves experiencing Al stress, thus ameliorating the Al toxicity of the latter. The results revealed that P application led to fixation of Al in the form of an Al–P precipitate in sand, thus relieving Al toxicity. In addition, the application of P increased the nutritive P supply and alleviated P deficiency within the plant. In Eucalyptus seedlings, increased P application to the root half without Al³⁺ exposure alleviated Al toxicity in the other root half. The extent of resistance to Al stress depended on the genotype of the Eucalyptus seedlings. Based on our findings, P can be applied to areas not only through roots, but also by other methods, such as leaf fertilization or application of nutrient solutions to the trunk, preferably avoiding the formation of Al–P precipitates in the soil.

摘要

全世界约30％的土地是酸性土壤（pH <5.5），铝（Al）毒性和磷（P）缺乏是酸性土壤中植物生长的两个主要限制因素。但是，在酸性土壤上直接施用磷肥会形成不溶性的Al-P沉淀，从而降低了磷的利用率。我们使用了分根技术，通过实验研究了桉树幼苗是否可以将P从无Al胁迫的根一半转移到遭受Al胁迫的根一半，从而减轻后者的Al毒性。结果表明，磷的施用导致以沙子中的Al–P沉淀形式固定Al，从而减轻了Al的毒性。另外，磷的施用增加了植物中营养性磷的供应并减轻了磷的缺乏。在桉树中幼苗中，在不暴露Al ^3+的情况下，增加对根半部的磷施用量可以减轻另一半根中的Al毒性。对铝胁迫的抗性程度取决于桉树幼苗的基因型。根据我们的发现，磷不仅可以通过根部施用到区域，还可以通过其他方法施用，例如叶面施肥或向树干施用营养液，最好避免在土壤中形成Al-P沉淀。