Effecct of manganese on the in vitro development and accumulation of iron and magnesium in Dendrobium kingianum Bidwill

The objective of the study was to determine the effect of increasing manganese concentrations, 2, 4, 8 and 16 times higher than the standard content in Murashige and Skoog (1962) medium, on morphological traits and on the accumulation of iron and magnesium in the roots and shoots of Dendrobium kingianum Bidwill. For micropropagation of orchid plants we used shoots placed on solid MS medium supplemented with 1.0 mg dm-3 kinetin and 0.5 mg dm-3 NAA, as well as different concentrations of manganese (as MnSO4· 4H2O): 22.3 (control), 44.6, 89.2, 178.4 and 356.8 mg dm-3. After 18 months of in vitro culture, the increased concentrations of manganese, from 44.6 to 356.8 mg dm-3 in the MS medium, had no stimulatory effect on orchid development in the in vitro culture. The greatest number and length of shoots and roots and the greatest fresh weight of plantlets were noted in the control. At the high manganese concentrations of 178.4 and 356.8 mg dm-3 in the MS medium, the number and length of these organs and the fresh weight of entire plantlets were statistically significantly lower than in the control. Spectrophotometric analysis (ASA) showed that as the manganese concentrations in the medium increased, there was an increase in the manganese content and a decrease in the iron and magnesium content in the orchid shoots and roots. Moreover, the iron accumulation in roots was 2-3 times greater than in shoots, while the magnesium accumulation was only 15-30% greater. In contrast to these metals, the accumulation of manganese was 2-3 times greater in the orchid shoots than in the roots.