Department of Plant Nutrition, China Agricultural University, Key Laboratory of Plant-Soil Interactions, Ministry of Education, Beijing 100193, PR China.
Ann Bot. 2010 Apr;105(4):585-93. doi: 10.1093/aob/mcq012. Epub 2010 Feb 11.
Phosphorus (P) is a major factor controlling cluster-root formation. Cluster-root proliferation tends to concentrate in organic matter (OM)-rich surface-soil layers, but the nature of this response of cluster-root formation to OM is not clear. Cluster-root proliferation in response to localized application of OM was characterized in Lupinus albus (white lupin) grown in stratified soil columns to test if the stimulating effect of OM on cluster-root formation was due to (a) P release from breakdown of OM; (b) a decrease in soil density; or (c) effects of micro-organisms other than releasing P from OM.
Lupin plants were grown in three-layer stratified soil columns where P was applied at 0 or 330 mg P kg(-1) to create a P-deficient or P-sufficient background, and OM, phytate mixed with OM, or perlite was applied to the top or middle layers with or without sterilization.
Non-sterile OM stimulated cluster-root proliferation and root length, and this effect became greater when phytate was supplied in the presence of OM. Both sterile OM and perlite significantly decreased cluster-root formation in the localized layers. The OM position did not change the proportion of total cluster roots to total roots in dry biomass among no-P treatments, but more cluster roots were concentrated in the OM layers with a decreased proportion in other places.
Localized application of non-sterile OM or phytate plus OM stimulated cluster-root proliferation of L. albus in the localized layers. This effect is predominantly accounted for by P release from breakdown of OM or phytate, but not due to a change in soil density associated with OM. No evidence was found for effects of micro-organisms in OM other than those responsible for P release.
磷（P）是控制根簇形成的主要因素。根簇的增殖往往集中在富含有机物（OM）的表层土壤层中，但根簇形成对 OM 的这种反应的性质尚不清楚。通过在分层土壤柱中种植白 Lupinus albus（白 Lupinus）来研究 OM 对根簇形成的刺激作用是否归因于（a）OM 分解释放的 P；（b）土壤密度降低；或（c）除从 OM 中释放 P 以外的微生物的影响，来对 OM 局部应用引起的根簇增殖进行了表征。
将 Lupinus albus 植物种植在三层分层土壤柱中，在 0 或 330 mg P kg(-1) 下施加 P，以创建 P 缺乏或 P 充足的背景，并将 OM、与 OM 混合的植酸或珍珠岩施加到顶层或中层，有无灭菌。
非无菌 OM 刺激根簇增殖和根长，并且当在 OM 存在下供应植酸盐时，这种作用变得更大。无菌 OM 和珍珠岩都显著降低了局部层中的根簇形成。在无 P 处理中，OM 位置并没有改变缺乏 P 处理中总根簇与总根的比例，但更多的根簇集中在 OM 层中，其他地方的比例降低。
局部应用非无菌 OM 或植酸盐加 OM 刺激 L. albus 在局部层中的根簇增殖。这种作用主要归因于 OM 或植酸盐分解释放的 P，但与 OM 相关的土壤密度变化无关。没有发现 OM 中除了负责 P 释放的微生物以外的微生物的影响。
