Investigating the Applications of Selenium on Water Productivity and Some Characteristics of Mentha piperita L. under Drought Stress

Water and moisture in the soil is one of the main factors in determining area under cultivation and as a result production of agricultural products, which is limited in arid and semi-arid areas such as Iran, this limitation and lack of water resources affects the performance of plants and especially Medicinal plants. Using deficit irrigation methods and promoting the concept of water productivity in the production of agricultural products is a practical and common method in different parts of the world to maintain and optimally use water resources. Water productivity actually expresses the amount of product or income. It is obtained from the water consumption unit. During their growth period, plants may face many environmental stresses that have different effects on their growth and performance based on the sensitivity and growth stage of the plant. Drought stress is one of the most important factors limiting the physiological and nutritional growth of plants. It is always necessary and important to know the combination or combinations that lead to reducing the effects of drought stress in plants. Although the toxicity of selenium in high concentrations is evident on plants and it is considered a type of stress, nevertheless, the beneficial effects of its low concentrations in protecting plants against non-living stresses through almost complex mechanisms have been identified. Nowadays medicinal and aromatic plants have received a lot of attention in various fields, including agriculture and pharmaceutical industries. Peppermint plant is a herbaceous and perennial plant that is considered as a medicinal and aromatic plant and is widely used in the pharmaceutical industry. The main purpose of this research is to compare and investigate the effect of selenium in different situations of its application (Mixing with irrigation water and foliar spraying before and after applying moisture stress) on water productivity and some properties of peppermint plant )Mentha piperita L) was under Drought Stress.
For this purpose and in order to investigate the effects of drought stress and different forms of selenium application on water productivity and some characteristics of Mentha piperita L, an experiment was performed in factorial form and in a completely randomized design and in three replications on Mentha piperita L in the research greenhouse university of Torbat-e Jam. The effects of drought stress include two levels 100 (I1) and 50 (I2) percent of water requirement and the application of selenium includes four levels (no application (zero), I (Mixing with irrigation water at the rate of 5 milligrams per liter of sodium selenate (, Leafbefore (Foliar application of selenium at the rate of 5 milligrams per liter of sodium selenate before applying moisture stress) and Leafafter (Foliar application of selenium at the rate of 5 milligrams per liter of sodium selenate after applying moisture stress) was investigated. In order to properly establish the seedlings, plants were irrigated once every other day for two weeks after the transfer of rhizomes. Then the process of applying the treatments began. In this way, in the treatment of selenium mixing with irrigation water, sodium selenate at the rate of 5 milligrams per liter was mixed with irrigation water and given to the desired pots in each irrigation cycle, and moisture stress treatments were also applied at the same time. Finally, after 5 weeks of selenium treatments and moisture stress, the plant was harvested. Also, in the Leafbefore treatment, the desired pots were treated with sodium selenate (Na2SeO4) with a concentration of 5 milligrams per liter as a foliar spray solution. Foliar spraying was done three times every other day and 24 hours after the last foliar spraying, the desired pots were subjected to moisture stress for 30 days and then the plant was harvested. Also, in the Leafafter treatment, after proper establishment of seedlings, the pots were first subjected to moisture stress, and after 30 days of applying moisture stress, foliar spraying of selenium at the rate of 5 milligrams per liter of sodium selenate three times as It was done every other day and one week after spraying the plant, the plant was harvested. The results of this research showed that with the increase of drought stress level from 100% of water requirement to 50% of water requirement, fresh weight, dry weight, percentage of essential oil, plant height, number of leaves and root fresh weight Mentha piperita L decreased by 34/95%, 33/64%, 34/53%, 29/35%, 34/17% and 33/61% respectively, and water productivity increased by 30/69%. Also, in the selenium treatments including Leafbefore, Leafafter and I, compared to the absence of selenium, water productivity 66/87%, 41/79% and 29/25% respectively increased. Among the selenium treatments, the Leafbefore treatment had the highest increase in fresh weight, dry weight, water productivity, essential oil percentage, plant height and number of leaves, and treatment I had the highest increase in the root fresh weight Mentha piperita L. The results showed that selenium in the concentration used in this research increased some properties of Mentha piperita L and was effective in reducing the effects of drought stress in this plant.