title: Response and tolerance of root border cells to aluminum toxicity in soybean seedlings.
abstract: Root border cells (RBCs) and their secreted mucilage are suggested to participate in the resistance against toxic metal cations, including aluminum (Al), in the rhizosphere. However, the mechanisms by which the individual cell populations respond to Al and their role in Al resistance still remain unclear. In this research, the response and tolerance of RBCs to Al toxicity were investigated in the root tips of two soybean cultivars [Zhechun No. 2 (Al-tolerant cultivar) and Huachun No. 18 (Al-sensitive cultivar)]. Al inhibited root elongation and increased pectin methylesterase (PME) activity in the root tip. Removal of RBCs from the root tips resulted in a more severe inhibition of root elongation, especially in Huachun No. 18. Increasing Al levels and treatment time decreased the relative percent viability of RBCs in situ and in vitro in both soybean cultivars. Al application significantly increased mucilage layer thickness around the detached RBCs of both cultivars. Additionally, a significantly higher relative percent cell viability of attached and detached RBCs and thicker mucilage layers were observed in Zhechun No. 2. The higher viability of attached and detached RBCs, as well as the thickening of the mucilage layer in separated RBCs, suggest that RBCs play an important role in protecting root apices from Al toxicity.
authors.affiliation: College of Geography and Environmental Sciences, Zhejiang Normal University, 688 Yingbin Road, Jinhua, Zhejiang, China. mzcai@zjnu.cn
authors.forename: Miao-Zhen
authors.initials: MZ
authors.lastname: Cai
authors.forename: Fang-Mei
authors.initials: FM
authors.lastname: Wang
authors.forename: Rong-Feng
authors.initials: RF
authors.lastname: Li
authors.forename: Shu-Na
authors.initials: SN
authors.lastname: Zhang
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.forename: Gen-Di
authors.initials: GD
authors.lastname: Xu
mesh_terms: D000535:Aluminum / Q000494:pharmacology*; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D057075:Enzyme Assays; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development; D058441:Rhizosphere; D036226:Seedlings / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development; D013025:Glycine max / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development
chemical_list: D000535:Aluminum; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase