Effects of Different Mineral Concentrations and Investigation on Lemon Verbena (Lippia citriondora L.B.K) Production under Hydroponic Conditions

Optimum nutrition is one of the most important factors that affecting quantity and quality of medicinal plants. Therefore, 4 formulation with different electrical conductivity (EC= 0.7, 1.4, 2.8 and 5.6 dSm-1) were investigated on vegetative characteristics, concentration and components of essential oil of lemon verbena in a soilless culture system. Based on our results, leaf fresh weight was affected by nutrition elements (p<0.05); so that the maximum and minimum fresh weight was observed at 1.4 and 5.6 dSm-1, respectively. With increasing in EC (more than 1.4 dSm-1) stomatal conductance and consequently net photosynthesis declined. Probably, decrease in fresh weight in response to high level of EC, resulted by decreasing in stomatal conductance and consequently decreasing in net photosynthesis. Essential oil content in lemon verbena increased synchronously with increasing in nutrition elements (p<0. 5); so that with an increasing in EC level from 1.4 to 2.8 dSm-1 and from 2.8 to 5.6 dSm-1, 37 and 45% of essential oil was increased, respectively. Geranial, neral and Alpha-curcumene were the main components of essential oil, and geranial was influenced by different formulation more than other components. These results led to conclution that optimum concentration of nutrient element has a key role on physiological factors, such as stomatal conductance, net photosynthesis, chlorophyll, proline, concentration and components of essential oil.