Changes in endogenous hormone levels and redox status during enhanced adventitious rooting by rare earth element neodymium of Dendrobium densiflorum shoot cuttings

The effects of neodymium nitrate (Nd3 ) on the adventitious rooting of Dendrobium densiflorum shoot cuttings were studied. The addition of Nd3 (5 μmol/L) to culture medium significantly increased rooting frequency. Histological investigation showed that Nd3 did not change the process of root initiation. Nd3 did not influence total endogenous cytokinin levels, but significantly increased the level of en-dogenous 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 Nd3 treatment. These results suggested that the enhanced rooting frequency may be related to the increase in endogenous IAA level in Nd3 treatment. Analysis of enzyme activities showed that the enhanced accumulation of the endogenous IAA by Nd3 should not be attributed to inhibition of IAA decomposition by IAA oxidase or promotion of cytokinin decomposition by cytokinin oxidase. Besides, Nd3 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.     

Ab initio calculation of electronic structures and 4f-5d transitions of some rare earth ions doped in crystal YPO4

The ab initio self-consistent DV-X_α (discrete variational X_α) method was used in its relativistic and spin-polarized model to investigate the ground-state electronic structures of the crystal YPO₄ and YPO₄:RE³⁺ (RE=Ce, Pr and Sm) and f-d transition energies of the lattice. The calculation was performed on the clusters Y₅P₁₀O₃₂ and REY₄P₁₀O₃₂ embedded in a microcrystal containing about 1500 ions, respectively. The ground-state calculation provided the locations of the 4f and 5d crystal-field one-electron levels of RE³⁺ relative to the valence and conduction bands of host, the curve of total and the partial density of states, and the corresponding occupation numbers, etc. Especially, the transition-state calculation was performed to obtain the 4f → 5d transition energies of RE³⁺ in comparison to the experimental observations. The lattice relaxation caused by the dopant ion RE³⁺ was discussed based on the total energy calculation and the transition-state calculation of the f-d transition energies.