Investigating the effect of different soil textures on morphological characteristics and the amount of essential oil of Lippia citriodora medicinal plant

Introduction The physical properties of soil are essential because of their role in supporting plant growth. These characteristics determine how the plant interacts with the soil, absorption of water and nutrients, root penetration, soil temperature, and the activity of microorganisms. Among the physical properties of soil, soil texture has a significant impact. On the other hand, with the increase in the population and the pharmaceutical industry's need for medicinal plants as the primary raw material for drug production, attention and research on the Lippia citriodora plant are essential. L. citriodora is effective in treating colds, asthma, colic, fever, diarrhea, dyspepsia, insomnia, and anxiety. L. citriodora tea is relaxing and soothing to the nerves. Its analgesic, anti-inflammatory, and antioxidant effects have been proven. Plants containing essential oil, such as L. citriodora may differ in yield and quality of oil according to the type of soil texture, so in order to achieve the highest yield of essential oil and the best quality, the soil should be adapted to the type and needs of the plant for better growth and development be provided. Therefore, the purpose of this research is to investigate the effects of different soil textures on the growth and development and the amount of essential oil of L. citriodora in greenhouse conditions. Materials and MethodsThis research has been carried out in pots in the research greenhouse of Yazd University in the crop year of 2017-2018. The experiment was conducted as a randomized complete block design in three replications for five months. Plastic pots with drains of 18 heights, opening diameter of 17 cm, and drain diameter of one cm were used for growing seedlings. The pots with different soil textures (loamy, sandy loam, sand, and silty clay loam) based on the calculation of the weight percent of soil moisture at the field capacity (FC) were irrigated. The length of the stem and roots were measured with a ruler with mm accuracy. A caliper was used to measure the thickness of the stem. The samples of shoots and roots were kept in an oven at 70 °C for 48 hr. A digital scale with an accuracy of 0.001 gr was used to measure the dry weight of the shoots and roots of the plants. In order to measure the root volume after separating and washing the roots, the roots of each replicate were placed inside a graded cylinder with a certain amount of water, and the volume of the root was measured in mm based on the chang