Effect of copper concentration on micropropagation and accumulation of some metals in the Dendrobium kingianum Bidwill orchid

The study focused on the influence of an increased copper content in the Murashige and Skoog (1962) solid medium on the in vitro plant growth and development of Dendrobium kingianum Bidwill. Sterile explants of pseudobulbs were used for micropropagation of orchid plants on the MS regeneration medium supplemented with 0.5 mg dm-3 NAA and 1.0 mg dm-3 kinetin. Copper (as CuSO4 × 5H2O) was added to all the combinations in concentrations of 0.025 (control), 0.625, 1.25, 2.5 and 5.0 mg dm-3. The results showed that the treatments with 1.25 and 2.5 mg dm-3 stimulated the orchid growth and development in in vitro culture. After eight months of growing in in vitro culture, the highest number of shoots, the longest roots and the heaviest fresh weight of plantlets were obtained in these treatments. In medium with the highest copper concentration (5.0 mg dm-3), a negative influence of the metal on the length of roots and fresh weight of orchids was noted. Spectrophotometric analysis (ASA) showed that the copper and iron accumulation increased in both shoots and roots with the increase in the external Cu level, whereas the zinc and calcium accumulation in these organs decreased. The copper and zinc accumulation in the roots was about 1.5-2.5 times higher than in the shoots, but the iron accumulation was about 3-3.5 times higher. The calcium accumulation in roots was only 5-12% higher than in shoots.