EFFECT OF NUTRIENT SOLUTION'S IRON CONCENTRATION ON GROWTH AND ESSENTIAL OIL CONTENT OF OREGANO PLANTS GROWN IN SOLUTION CULTURE

An experiment was done with oregano [Origanum vulgare spp. hirtum (Link) Ietswaart] grown in NFT under 3 different target levels (2.5, 5.0 and 11.0 mg/l) of Fe-EDTA in the nutrient solution to study the effect of iron on growth and essential oil content of the plants. Iron uptake by plants was associated with the Fe concentration in the nutrient solution and the uptake rate during the growing season was maximal in the seed formation stage. Iron content in leaves and roots increased with increasing Fe concentration in the nutrient solution. Top (younger) leaves had less iron content than the older ones. Roots presented much higher accumulation of iron than leaves. Increasing iron concentration to 11.0 mg/l resulted in decreased plant growth parameters (fresh and dry mass of shoots, dry mass of roots), but increased the ratio of dry leaves/stem. Essential oil content of the shoots decreased in the highest (11.0 mg/l) Fe nutrient solution concentration. It can be concluded that under the conditions of the experiment the high iron concentration applied reduced both biomass and essential oil yield.