摘要
The effects of neodymium nitrate （Nd^3＋） on the adventitious rooting of Dendrobium densiflorum shoot cuttings were studied. The addition of Nd^3＋ （5 μmol/L） to culture medium significantly increased rooting frequency. Histological investigation showed that Nd^3＋ did not change the process of root initiation. Nd^3＋ did not influence total endogenous cytokinin levels, but significantly increased the level of endogenous indole-3-acetic acid （IAA） in the base of shoot cuttings. Compared to the control, the ratio of IAA/cytokinins was very high in the Nd^3＋ treatment. These results suggested that the enhanced rooting frequency may be related to the increase in endogenous IAA level in Nd^3＋ treatment. Analysis of enzyme activities showed that the enhanced accumulation of the endogenous IAA by Nd^3＋ should not be attributed to inhibition of IAA decomposition by IAA oxidase or promotion of cytokinin decomposition by cytokinin oxidase. Besides, Nd^3＋ increased the ratio of reduced glutathione （GSH） and oxidized glutathione （GSSG） in the process of adventitious rooting while the ratio of ascorbate （ASC） to dehydroascorbate （DHA） was not affected.
The effects of neodymium nitrate （Nd^3＋） on the adventitious rooting of Dendrobium densiflorum shoot cuttings were studied. The addition of Nd^3＋ （5 μmol/L） to culture medium significantly increased rooting frequency. Histological investigation showed that Nd^3＋ did not change the process of root initiation. Nd^3＋ did not influence total endogenous cytokinin levels, but significantly increased the level of endogenous indole-3-acetic acid （IAA） in the base of shoot cuttings. Compared to the control, the ratio of IAA/cytokinins was very high in the Nd^3＋ treatment. These results suggested that the enhanced rooting frequency may be related to the increase in endogenous IAA level in Nd^3＋ treatment. Analysis of enzyme activities showed that the enhanced accumulation of the endogenous IAA by Nd^3＋ should not be attributed to inhibition of IAA decomposition by IAA oxidase or promotion of cytokinin decomposition by cytokinin oxidase. Besides, Nd^3＋ increased the ratio of reduced glutathione （GSH） and oxidized glutathione （GSSG） in the process of adventitious rooting while the ratio of ascorbate （ASC） to dehydroascorbate （DHA） was not affected.
基金
supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (20060359006)
