Iijima Morio, Griffiths Bryan, Bengough A Glyn
1 Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
New Phytol. 2000 Mar;145(3):477-482. doi: 10.1046/j.1469-8137.2000.00595.x.
Sloughing of root cap cells and exudation of mucilage plays an important role in the penetration of compacted soils by roots. For the first time we have quantified the rate of sloughing of root cap cells in an abrasive growth medium that was compacted to create mechanical impedance to root growth. The number of maize (Zea mays) root cap cells sloughed into sand increased as a result of compaction, from 1930 to 3220 d per primary root. This represented a 12-fold increase in the number of cells sloughed per mm root extension (from 60 to >700). We estimated that the whole of the cap surface area was covered with detached cells in compacted sand, compared with c. 7% of the surface area in loose sand. This lubricating layer of sloughed cells and mucilage probably decreases frictional resistance to soil penetration. The total carbon deposited by the root was estimated at c. 110 μg g sand d . Sloughed cells accounted for <10% of the total carbon, the vast majority of carbon being contained in mucilage exudates.
根冠细胞的脱落和黏液的分泌在根系穿透紧实土壤的过程中起着重要作用。我们首次在一种紧实的、对根系生长产生机械阻抗的砂质生长培养基中，对根冠细胞的脱落速率进行了量化。由于土壤紧实，每根初生根每天脱落到砂中的玉米（Zea mays）根冠细胞数量从1930个增加到3220个。这意味着每毫米根伸长脱落的细胞数量增加了12倍（从60个增加到700多个）。我们估计，在紧实砂中，根冠的整个表面积都被脱落的细胞覆盖，而在疏松砂中这一比例约为7%。这种由脱落细胞和黏液形成的润滑层可能会降低根系穿透土壤的摩擦阻力。根系沉积的总碳量估计约为110 μg g砂 d。脱落细胞占总碳量的比例不到10%，绝大多数碳包含在黏液分泌物中。
