黑豆边缘细胞对干旱胁迫的响应和对根系生理特性的影响

以黑豆Glycine max (L.) Merrill为材料,采用静置培养(保持边缘细胞和黏液附着在根尖)和振荡培养(移除边缘细胞及根尖黏液)方法,比较研究干旱胁迫下黑豆根尖边缘细胞(root border cells, RBCs)产生和黏液分泌以及对根系生理特性的影响。结果表明,与对照相比,11%和22%的聚乙二醇(PEG)处理使RBCs数目分别降低了18.1%～21.6%和28.8%～30.4%,胞外黏液分泌分别增加了62.8%～140.7%和133.8%～172.7%,表明干旱胁迫抑制了RBCs的发育,增加了RBCs黏液分泌量。移除边缘细胞的根伸长抑制率、根系相对电导率和丙二醛(MDA)含量高于保留边缘细胞的根,而根系脯氨酸含量则是前者显著低于后者。说明干旱胁迫下,黑豆根尖附着的RBCs及黏液分泌量的增加,减缓了根尖细胞损伤,有利于根系生长,从而提高黑豆的抗旱能力。

Response of root border cells to drought stress and their effects on physiological characteristics of roots of black soybean seedlings

Root border cells and root cap cells secrete mucilage into root rhizosphere which acts as a chemical, physical and biological interface between roots and their surrounding environment. The effects of root border cells (RBCs) and root mucilage on protection of roots from drought stress were carried out by two cultivation methods, a shaking cultivation method to remove RBCs from root tips and a static cultivation method to maintain RBCs adhered to the root tips. Compared to the control, the root elongations are decreased by about 18.1~21.6% and 28.8~30.4% , respectively under the treatments of the roots with 11% and 22% PEG, while the thicknesses of the mucilage layer around RBCs are increased by about 62.8%~140.7% and 133.8%~172.7%. These results suggest that the drought stress inhibits RBCs development and enhances mucilage secretion. The physical removal of RBCs from root tips results in a more severe drought-induced inhibition of root elongation, relative electric conductivity and malondialchehyche (MDA) content. The proline content in roots of black soybean with RBCs removed is significantly lower than that in roots with RBCs surrounding. These results suggest that RBCs adhered to the root tips tend to enhance RBCs’ mucilage secretion, decrease the damage to root cells, promote root growth, and thereby promote drought tolerance in black soybean seedlings.