Investigation of Germination Characteristics of Four Medicinal Plants Seed (Lavender, Hyssop, Black cumin and Scrophularia) Under Interaction Between Salinity Stress and Temperature Levels

Medicinal plants are stores of active and valuable secondary metabolites that have been economically beneficial for pharmacy and medicine. However, it is challenging to start large-scale and commercial cultivation of these plants since most of the arable land is mainly used to produce strategically essential crops. Other uncultivable lands are often affected by various abiotic stresses, one of the most important of which is salinity. Germination of plants is one of the critical stages during their growth period that is often affected by environmental stresses, especially salinity. In the present study, the seeds of medicinal plants such as Lavender (Lavandula angustifolia), Hyssop (Hyssopus officinalis), Black cumin (Nigella sativa L.), and Scrophularia (Scrophularia striata) were subjected to salinity stress at 20, 25, and 30 °C to determine the germination characteristics of their seeds. At each temperature, to create salinity stress, five levels of salinity potential, including 0, 50, 100, 150, and 200 mM NaCl were applied, prepared using sodium chloride salt with the required amounts. The results of this experiment generally showed that with increasing salinity concentration at different temperatures, all germination characteristics, including germination percentage, germination rate, shoot length, root length, shoot dry weight, dry root weight, and seed vigor index, decreased. Salinity stress is one of the most important abiotic stresses in areas with saline soil and water, which reduces the quality and yield of plants, especially medicinal plants, and weakens them against other environmental stresses. It seems that low salinity soil and water are needed to get the best yield for the commercial growth of plants.