Effect of water stress and humic acid foliar application on morpho-physiological characteristics of Satureja hortensis

Satureja hortensis plant is a medicinal, annual, Herbaceous belonging to the family Lamiaceae, which is used as a medicinal plant and spice, as well as fresh vegetable. Various plant species show a wide range of resistance to drought due to their physiological, morphological and biochemical adaptations. The use of various organic fertilizers, including humic acid, has been widely used to improve the quality and quantity of crops and gardens without harmful environmental effects. Hormonal effects and enhancement of the absorption of nutrients to enhance performance, especially under stress conditions, are the effects of humic acid is derived from humus and other natural sources and Growth stimulating bacteria. Considering the dry and semi-dry nature of a large area of Iran, it is necessary to save water; on the other hand, nutrition is important in the yield and quality of the effective materials of medicinal plants. Therefore, the purpose of this study was to investigate the effects of drought stress and humic acid on morphological and physiological characteristics of Satureja hortensis. The experiment was a factorial based on a completely randomized design with four replications in greenhouse conditions in 2017. Four levels of irrigation water regulations 40, 60, 80 and 100% of field capacity and foliar application of humic acid in concentrations of 0, 150, 300 and 450 mg/L were applied. In the 6 to 8 leaves stage, Drought treatments were applied to the pots. Humic acid was applied in two stages in the desired concentrations. The first stage of spraying was when the plants were in the 4 to 6 leaves stage and the second stage was done two weeks after the first spraying. About 7 weeks after application of drought treatments, traits such as plant height, number of branches, number of leaves, leaf length, plant dry weight, proline, chlorophyll a, b and total, carotenoid and carbohydrates were measured. The results showed that the highest plant height, leaf number, number of branches and plant dry weight were obtained under irrigation conditions at 100% FC and spraying with 450 mg/l humic acid; While the highest leaf length, chlorophyll a, b and total, carotenoid and carbohydrate were obtained from irrigation treatment at 100% FC and 300 mg / l humic acid. Also, the highest proline content was obtained from irrigation treatments at 40% FC without humic acid application. Satureja hortensis plant is susceptible to drought stress and with increasing stress and reaching 40% of FC, decrease in the amount of physiological and morphological traits of Satureja hortensis. Meanwhile humic acid had a positive and significant effect on these traits. Finally, by improving the absorption of nutrients and the development of Vegetative and reproductive parts, the physiological and morphological traits increased. The highest effect of humic acid treatment on drought stress of Satureja hortensis was in the treatment of 450 mg/l. The highest salinity production was obtained in irrigation treatment with 100% FC and 450 mg/l humic acid.