Iijima Morio, Higuchi Toshifumi, Barlow Peter W
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
Ann Bot. 2004 Sep;94(3):473-7. doi: 10.1093/aob/mch166. Epub 2004 Jul 26.
The impedance to root growth imposed by soil can be decreased by both mucilage secretion and the sloughing of border cells from the root cap. The aim of this study is to quantify the contribution of these two factors for maize root growth in compact soil.
These effects were evaluated by assessing growth after removing both mucilage (treatment I -- intact) and the root cap (treatment D -- decapped) from the root tip, and then by adding back 2 micro L of mucilage to both intact (treatment IM -- intact plus mucilage) and decapped (treatment DM -- decapped plus mucilage) roots. Roots were grown in either loose (0.9 Mg m(-3)) or compact (1.5 Mg m(-3)) loamy sand soils. Also examined were the effects of decapping on root penetration resistance at three soil bulk densities (1.3, 1.4 and 1.5 Mg m(-3)).
In treatment I, mucilage was visible 12 h after transplanting to the compact soil. The decapping and mucilage treatments affected neither the root elongation nor the root widening rates when the plants were grown in loose soil for 12 h. Root growth pressures of seminal axes in D, DM, I and IM treatments were 0.328, 0.288, 0.272 and 0.222 MPa, respectively, when the roots were grown in compact soil (1.5 Mg m(-3) density; 1.59 MPa penetrometer resistance).
The contributions of mucilage and presence of the intact root cap without mucilage to the lubricating effect of root cap (percentage decrease in root penetration resistance caused by decapping) were 43 % and 58 %, respectively. The lubricating effect of the root cap was about 30 % and unaffected by the degree of soil compaction (for penetrometer resistances of 0.52, 1.20 and 1.59 MPa).
土壤对根系生长的阻抗可通过黏液分泌以及根冠边缘细胞的脱落来降低。本研究旨在量化这两个因素对紧实土壤中玉米根系生长的贡献。
通过评估根尖去除黏液(处理I——完整)和根冠(处理D——去冠)后的生长情况,然后向完整(处理IM——完整加黏液)和去冠(处理DM——去冠加黏液)根系中回加2微升黏液来评估这些效应。根系在疏松(0.9 Mg m(-3))或紧实(1.5 Mg m(-3))的壤质砂土中生长。还研究了在三种土壤容重(1.3、1.4和1.5 Mg m(-3))下去冠对根系穿透阻力的影响。
在处理I中,移植到紧实土壤12小时后可见黏液。当植株在疏松土壤中生长12小时时,去冠和黏液处理对根系伸长率和增粗率均无影响。当根系在紧实土壤(1.5 Mg m(-3)密度;贯入阻力1.59 MPa)中生长时,D、DM、I和IM处理中胚轴的根系生长压力分别为0.328、0.288、0.272和0.222 MPa。
黏液以及无黏液的完整根冠对根冠润滑效应(去冠导致的根系穿透阻力降低百分比)的贡献分别为43%和58%。根冠的润滑效应约为30%,且不受土壤紧实度程度的影响(贯入阻力为0.52、1.20和1.59 MPa时)。