CSIRO Plant Industry, Canberra, Australian Capital Territory 2601, Australia.
Plant Cell Environ. 2010 Feb;33(2):133-48. doi: 10.1111/j.1365-3040.2009.02059.x. Epub 2009 Nov 4.
We analysed the abundance, spatial distribution and soil contact of wheat roots in dense, structured subsoil to determine whether incomplete extraction of subsoil water was due to root system limitations. Intact soil cores were collected to 1.6 m below wheat crops at maturity on a red Kandosol in southern Australia. Wheat roots, remnant roots, soil pores and root-soil contact were quantified at fresh breaks in the soil cores. In surface soil layers (<0.6 m) 30-40% of roots were clumped within pores and cracks in the soil, increasing to 85-100% in the subsoil (>0.6 m), where 44% of roots were in pores with at least three other roots. Most pores contained no roots, with occupancy declining from 20% in surface layers to 5% in subsoil. Wheat roots clumped into pores contacted the surrounding soil via numerous root hairs, whereas roots in cracks were appressed to the soil surface and had very few root hairs. Calculations assuming good root-soil contact indicated that root density was sufficient to extract available subsoil water, suggesting that uptake is constrained at the root-soil interface. To increase extraction of subsoil water, genetic targets could include increasing root-soil contact with denser root hairs, and increasing root proliferation to utilize existing soil pores.
我们分析了密植、结构化的底土中小麦根系的丰度、空间分布和与土壤的接触情况，以确定是否由于根系系统的限制导致未能完全从底土中提取水分。在澳大利亚南部的红色 Kandosol 上，当小麦作物成熟时，我们从 1.6 米深处采集完整的土壤芯。在新鲜的土壤芯断裂处对小麦根系、残余根系、土壤孔隙和根土接触进行定量分析。在表层土壤层（<0.6 米）中，有 30-40%的根系聚集在土壤中的孔隙和裂缝中，在底土（>0.6 米）中增加到 85-100%，其中有 44%的根系位于至少有其他三根根系的孔隙中。大多数孔隙中没有根系，其占有率从表层的 20%下降到底土的 5%。聚集在孔隙中的小麦根系通过许多根毛与周围土壤接触，而裂缝中的根系紧贴土壤表面，根毛很少。假设良好的根土接触的计算表明，根密度足以提取可用的底土水，这表明吸收受到根土界面的限制。为了增加底土水的提取，可以将遗传目标包括增加根土接触的密集根毛和增加根系增殖以利用现有的土壤孔隙。
