Abstract:

【Objective】 An experiment on root tip tolerance of non-transgenic control (CK) and citrate synthase (CS) transgenic plants from Medicago sativa L. cv. Yumu No.1 was conducted to find out the suitable conditions for Al-tolerance and to examine the Al-tolerance of the transgenic plants relative to the control plants. 【Method】 Using CS transgenic alfalfa No.4 and the control plant as materials, five AlCl3 concentration gradients were designed which were 0, 5, 15, 30, and 50 μmol?L-1, each with three replicates, the root tip elongation in the first three days was measured. 【Result】 The root tip elongation of transgenic and control plants on the first day was significantly higher than on the second and the third day in all five AlCl3 concentrations. The root tip elongation of transgenic plants at 15, 30, and 50 μmol?L-1 AlCl3 concentrations on second day was significantly higher than on the third day, while the root tip of control plant almost stopped elongating on the second and third day. With increased Al concentrations, the root tip elongation was inhibited seriously. The root tip of control plants in 15 μmol?L-1 Al treatment could elongate normally on the first day, while the elongation was seriously suppressed even if in 5 μmol?L-1 Al treatment on second day, indicating that the Al concentration the control plants could be tolerant of was less than 15 μmol?L-1. When the AlCl3 concentration increased to 30 μmol?L-1, the root tip elongation of transgenic plants was significantly suppressed (P＜0.05). 【Conclusion】 Al-tolerance conditions of transgenic alfalfa in Medicago sativa L. cv. Yumu No.1 were 15-30 μmol?L-1 AlCl3 concentrations for 2 days. Compared to the control, the transgenic alfalfa showed a significant resistance to Al.

Key words: Medicago sativa L., transgenic, citrate synthase, aluminum tolerance