Evaluation of Some Morphological Characteristics, Water Use Efficiency and Essential Oil of Basil (Ocimum basilicum var. keshkeni luvelou) under Application of Malva Leaves and Superabsorbent Polymer

Medicinal plants are rich in active substances and primarily have been used in the manufacture of many drugs. Basil (Ocimum basilicum L.) is one of the important medicinal plants whichbelongs to the Lamiaceae family. Basil essential oil content (between 0.5 to 1.5 percent) varies according to climatic conditions of habitat location. Basilneeds a lot of water during growth period and it is very sensitive to water stress and shows wilting symptoms very soon after water shortage. Iran is located in an arid and semi-arid region which has little precipitation that is not enough for crop water requirements. Nowadays, the use of superabsorbent polymers is one of the ways to create sustainable agriculture and increase irrigation efficiency. They can store high water or aqueous solutions in root zone of plants and to reduce negative effects of drought stress. So, improvement of plant growth, increasing of irrigation intervals, reducing water loss and costs of irrigation is due to the application of superabsorbent polymers. Mucilages are also the herbal polysaccharides, soluble in water, and commonly include carbohydrates and can be used as hydrophilic polymers. The aims of this investigation were to study the effects of hydrophilic polymers on water use efficiency, morphological characteristics (dry matter, leaf area, and leaf number), essential oil quantity and yield of basil to harden plant to drought stress and to evaluate its potential to cultivate in arid regions. In addition, taking steps forward towards sustainable agriculture, by reducing the cost of agricultural production, helps protecting the environment.
This research was conducted as a pot experiment at the department of Horticultural Science‚ college of Agricultural‚ Ferdowsi University of Mashhad‚ Iran, during 2012-2013.The research was set out in a factorial experiment on the basis of completely randomized block design with three replications.Two hydrophilic polymer Stockosorb® (industrial) and malva leaf (herbal) with two application methods (mixed with soil, mixed with soil꺊) at 4concentrations (0, 0.1%, 0.2% and 0.3% w/w) were used. Leaf number, leaf area, dry matter yield, water use efficiency, essential oil quantity and yield were measured. Improved seeds of Ocimum basilicum var. Keshkeniluvelou were sown and seedlings were transplanted to the pots in four-leaf stage. Hydrogels were prepared and mixed with water after weighing the polymers according to determined concentration. After establishment, all pots were irrigated with a determined amount of water after reaching to the highest concentration (0.3%) of the wilting point. So, in this state in addition to the treatment at 0.3% treatment, lower levels (0.2% and 0.1%)were reached to wilting point earlierand were exposed to water stress.
Superabsorbent polymers can by absorption of irrigation and rain water, prevent deep percolation of water and with decreasing irrigation interval and reduced water consumption and increase water use efficiency. The results showed that using Stockosorb superabsorbent polymer and malva leaf as herbal hydrophilic polymersare useful for water supply of the plant in water stress.Application of these substances on morphological characteristics, water use efficiency and basil oil, were superior to the control.According to the obtained results, malva leaf use in soil and roots in treatmentless than (0.1% and 0.2%)number and leaf area and higher than (0.3%)increased dry matter yield, water use efficiency and the essential oil quantity and yield. Stockosorb (0.2%) byboth applying methods increased dry matter yield and water use efficiency. Also Stockosorb (0.2%),soil application increased leaf number and area. The essential oil yield and quantity increasedwith use of Stockosorb in soil root in for0.2% and 0.3% treatments, respectively.
Due to the importance of cultivation of medicinal plants to provide conditions to increase essential oil yield and quantity at the same time, the best method used were malva leaf and Stockosorb with concentrations higher than (0.3%) and soil application methodor the use of both polymers with application method in soil root in the moderate concentration (0.2%).For that purpose, we obtained favorable conditions for improving the morphological characteristics, water use efficiency and increasing the quantity and of essential oil yield in drought stress simultaneously. The results showed that natural compounds can be a good alternative for chemical compounds, but further experiments are needed for their commercialization.