根际动态过程与植物营养

养分的有效性是由土壤物理、化学和生物学特性,特别是根系主导的根际动态过程所决定的。根系引起根际pH值和氧化还原电位、根分泌物以及由此引起微生物种群、数量和活性的改变,从根本上决定着根际养分的动态。而根系主导的根际动态又具有明显的基因型差异,并受植物营养状况的诱导和调控。因此,根际动态变化的方向和强度对植物适应土壤化学和物理逆境具有重要意义。本文从根际的一般概念入手,综述了近十余年来国内外根际动态研究的新成果,重点讨论了根际动态与植物营养的关系,并运用根际微生态系统的概念,把根际动态与植物对养分胁迫的适应性及其调控机理紧密联系起来,使根际动态和植物矿质营养基因型差异机理两个基础性研究热点融为一体,为解决重大的全球性环境、生态以及农业持续发展问题提供新的途径和理论依据。

RHIZOSPHERE DYNAMICS AND PLANT NUTRITION

The availability of mineral nutrients for plants is determined by the chemical, physical and biological characteristics of soils, especially by root-induced changes in the rhizosphere. Mineral nutrient supply to the root surface is mediated mainly by mass flow or diffusion. Accordingly, root surface area is important for the acquisition of nutrients. Acquisition of most nutrients is particularly dependent upon root-induced changes in rhizosphere pH, redox potential and the release of low molecular weight organic solutes. Depending on their chemical nature, these solutes can mobilise mineral nutrients directly, in the case of organic acids and phytosiderophores, or indirectly, by enhancing the activity of microorgpnisms in the rhizosphere. Rhizosphere microorganisms may, however, also decrease nutrient availability or affect nutrient acquisiton via changes in root morphology caused by hormones or by the infection of plant roots with mycorehiza. Root-induced changes in the rhizosphere vary between genotypes, and are affected by the nutritional status of the plant (e.g. phosphorus or iron deficiency). The extent of root-induced changes in the rhizosphere is important for adaptation of higher plants to soils with extreme themical and physical properties.