Influence of vitamins on growth performance of in vitro cultured Magnolia sp.

Bulgarian. The present work was undertaken to elucidate the effect of vitamins and their precursors on the physiological performance of in vitro proliferated Magnolia soulangeana and Magnolia grandiflora. Microplants were grown on Chee and Pool (C2D) Vitis (VM) basal medium supplemented with different concentrations of nicotinic acid, gly-cine, pyridoxine, thiamine, ascorbic acid and myo-inositol. The physiological behavior of explants was evaluated by development of axillary shoots and leaves and fresh and dry weights. The effects of combinations of VM with 10 mg/l myo-inositol, 1 mg/l nicotinic acid, 1 mg/l pyridoxine HCl and 1 mg/l thiamine HCl and VM vitamins) and VM supplemented with standard MS vitamins (100 mg/l myo-inositol; 2 mg/l glycine; 0.5 mg/l nicotinic acid; 0.5 mg/l pyridoxine HCl; 0.1 mg/thiamine HCl l) were compared to basal medium lacking vitamins. Besides, nicotinic acid, glycine, pyridoxine HCl and thiamine HCl were applied alone in concentrations of 0.1, 0.5, 1.0 and 2.0 mg/l added to VM basal salts. Ascorbic acid was used at 1, 2, 5, 10 and 50 mg/l. Myo-inositol was tested in a range of 10, 50, 100 and 200 mg/l. It was established that the plants growing on medium without vitamins showed statistically similar results to those growing on medium supplemented with vitamin mix MS. The plants cultured on VM supplemented with VM vitamin mix showed improved growth parameters in comparison to those cultured on medium without vitamins or enriched with vitamin mix MS. The strongest positive effect for both studied genotypes was established on VM medium containing 1 mg/l nicotinic acid, 2 mg/l thiamine HCl and 0.1 mg/l glycine. However, the growth response to ascorbic acid differed between the species. For M. soulangeana best effect was determined at concentration of 5 mg/l, whereas for M. grandiflora 10 mg/l appeared as most appropriate. No significant difference of plantlets growth was observed in dependence on the concentration of pyridoxine HCl, whereas in presence of all tested concentrations of myo-inositol the microplants showed worse characteristics than the ones cultured on medium lacking vitamins.In general, the tested concentrations of vitamins exerted the strongest effect on fresh and dry weight and height of microplants and least affected were the number of axillary shoots and leaves. From this study we conclude that the studied magnolia species differ relatively little in their requirements for the type and concentration of vitamins in the composition of the nutrient medium. However, our results indicate that the standard compositions of MS and VM vitamins are not the optimal for the studied geno¬types. The unsatisfactory effect of these compositions on growth and development might be eventually attributed to the relatively high myo-inositol concentration, which was found to reduce the quality of the plants in both spe¬cies. Our findings demonstrate that for the efficient development of magnolia species under in vitro conditions the most important of the tested compounds are nicotinic acid, thiamine, glycine and ascorbic acid.