Evaluation of the root-border-cells function in rhizosphere to decrease soil mechanical impedance.

在压实土壤中生长的植物根系必须克服土壤对根系伸长的机械阻抗。根缘细胞层的存在可以减小土壤与生长中的根之间的摩擦。我们试图评价根缘细胞对降低土壤机械阻抗的作用。在这一系列的实验中，我们发现了以下几点：1。我们首次量化了根缘细胞在磨料培养基中的脱落率。由于压实作用，玉米根缘细胞的数量从1930 d^<-1>增加到3220 d^<-1> /主根。在压实砂土中，整个帽盖表面都覆盖着分离细胞，而在松散砂土中，这一比例约为7%。2. 我们开发了一种图像分析程序来量化根冠中纵剖面上的细胞位置。根最外层仅有7%的细胞与帽部小柱区相关。机械阻抗略微增强了根冠外侧区域的分生组织活动。致密状态下的细胞生成率为2010个细胞d^<-1>，松散状态下为1570个细胞d^<-1>。4. 根冠的存在减轻了根系渗透的机械阻抗，使根系在压实土壤中生长得更快。5. 根缘细胞对根冠降低土壤阻力的贡献为58%。6. 研究了一种从土壤颗粒中分离根缘细胞的方法。湿土的根缘细胞数量显著大于干土。综上所述，根缘细胞的润滑层降低了土壤渗透的摩擦阻力。

Plant roots grown in compacted soils have to overcome the mechanical impedance of the soil to root elongation. The friction between soil and the growing root may be decreased by the layer of root border cells. We tried to evaluate the role of the root border cells to decreasing the soil mechanical impedance. In the series of experiment, we found the following:1. For the first time, we quantified the rate of sloughing of root border cells in an abrasive growth medium. The number of maize root border cells increased as a result of compaction, from 1930 to 3220 d^<-1> per primary root. The whole of the cap surface area was covered with detached cells in compacted sand, compared with about 7% of the surface area in loose sand. 2. We developed an image analysis procedure to quantify cell locations in the median longitudinal section of root caps. Only 7% of cells in the outermost layer of the root were associated with the columella region of the cap. 3. Mechanical impedance slightly enhanced meristematic activities in the lateral region of the root cap. Cell production rates were 2,010 cells d^<-1> in compact and 1,570 cells d^<-1> in loose. 4. The presence of a root cap alleviates much of the mechanical impedance to root penetration, and enables roots to grow faster in compacted soils. 5. The contribution of root border cells to the reduction in soil resistance by the presence of root cap was 58%. 6. A technique was developed to separate root border cells from soil particles. The number of root border cells in wet soil was significantly greater than that in the dry soil.In conclusion, the lubricating layer of root border cells decreases frictional resistance to soil penetration.