The Effect of Water Stress on Evapotranspiration and Morphological Characteristics of Satureja Hortensis

Regarding the importance of medicinal plants cultivation such as Satureja hortensis and the state of the country's water resources, determination of medicinal plants' evapotranspiration, essential oil content and yield is very important under water stress. As, no comprehensive research has been done on determining evapotranspiration, essential oil content and morphological factors of Satureja hortensis under drought stress conditions, an experiment was conducted at research field of  Agricultural faculty in Lorestan University in 2017. For this purpose, mini lysimeters (pots with 25 cm in diameter and 30 cm in height) were used. In this research, irrigation was done by weighing method. Irrigation treatments included T100: supplying 100% of water requirement, T80: supplying 80% of water requirement, T60: supplying 60% of water requirement and T40: supplying 40% of water requirement. The results showed that all morphological characteristics (plant height, number of branches, stem diameter, as well as dry weight of leaf and flowering shoot, roots and stems) decreased significantly under water stress conditions. The dry matter (consist of leaf, flower and branch) in all treatments from T100 to T40 were 1731.92, 1640.9, 1529.9 and 1408.6 kg/ha, the essential oil percent were 1.08, 1.3, 1.58 and 2% and the amount of evapotranspiration were 758.68, 653.75, 566.47 and 479.208 mm, respectively. In T40 treatment the biomass decreased by 19%, the essential oil percent became double and water use efficiency increased by 29%. In this study, the yield response factor to water stress was estimated to be 0.61. According to this value, it seems Satureja hortensis is relatively resistant to water stress (under the condition of using pots).