| heal.abstract |
In order to study the pattern of in vitro accumulation of selected micronutrients in mistletoe (Viscum album L.) callus cultures, we inoculated leaf and stem explants on a Murashige and Skoog (MS) medium supplemented with different combinations of plant growth regulators at various concentrations. The accumulation of manganese (Mn), zinc (Zn), copper (Cu), and boron (B) in mistletoe callus cultures was significantly affected by both plant growth regulator (PGR) treatment and explant source, as well as their interaction. However, neither of these factors affected Fe accumulation in a statistically significant sense. The average concentration of iron (Fe), Mn, Zn, and Cu in vitro was higher in stem-derived callus cultures than in leaf-derived calli, and much higher than in mistletoe plants and in mistletoe hosts, such as fir, oak and chestnut. For stem-derived calli and with the exception of B, application of 4.65 μM potassium (K) was superior to other PGR treatments leading to the maximum in vitro accumulation of the selected micronutrients. Except for B, the accumulation of micronutrients in stem-derived callus cultures was highly correlated with dry weight concentration; a high positive correlation was also observed among Fe, Mn, Zn, and Cu concentration, while B accumulation was slightly negatively correlated with the other micronutrients. On the contrary, in leaf-derived cultures, a high positive correlation was observed only between Mn and Cu concentration. The concentration of the selected micronutrients fluctuated during a total incubation period of 10 weeks on MS+4.95 μM α-naphthylacetic acid (NAA), with an increasing trend after the eighth week (B concentration being again an exception). Finally, the addition of ascorbic acid to the culture medium generally promoted micronutrient accumulation, in particular Mn and Cu in stem-derived cultures and Fe, Zn, and B in leaf-derived calli. This effect was correlated with an increase in total free phenolics substances, and further discussed in view of various plant antioxidant systems in vitro. |
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