عنوان مقاله [English]
Medicinal plants are in use by a large portion of population for their medicinal therapeutic effects. Borage (Borago officinalis L.) is an annual herbaceous, and hairy medicinal plant which height changes within 70 to 100 cm. Stems are straight, often branched, hollow, and covered by tough fibers. Its leaves are alternate and simple and are covered with tough fibers. The flowers are blue and rarely appear white or rose colored. This plant belongs to the family of Boraginaceae. The plant is also commercially cultivated for borage seed oil extracted from its seeds. Water is one of the important factors affecting growth and yield of medicinal plant. Increasing plant production per unit of water is one of the greatest challenges facing the researchers especially in arid and semi- arid regions. Plant density is an important agronomic factor that manipulate micro environment of the field and impacts growth, development and yield of plants. Within certain limits, increase of plant population density decreases the growth and yield per plant but the reverse occurs for yield per unit area. The optimum plant density to attain highest yield may vary with the plant and geographical location. Present study aims to investigate the possibility of improving the yield and yield components of borage affected as irrigation levels and plant densities.
Materials and Methods
A field experiment was conducted as split plot experiment based on a complete randomized block design (CRBD) with three replications at Agricultural Research Station, College of Agriculture, Ferdowsi University of Mashhad, Iran, during growing season of 2012-2013. Three irrigation levels (1000 (I1), 2000 (I2) and 3000 (I3) m3.ha-1) and four plant densities (16 (D1), 20 (D2), 26.67 (D3), 40 (D4) plants.m-2) allocated to the main plot and sub plot, respectively. Water requirement for the medicinal plant under Mashhad climatic conditions was determined by using AGWAT equal to 2000 m3.ha-1. When the plants were yellow harvesting operation was performed. At first, five plants per plot were randomly selected for measurement of yield components. After removal of margins, to determine the seed yield, the remaining area was harvested. The studied criteria were number of flowers, flower yield, biological yield, seed yield, number of seed, 1000-seed weight and number of branches per plant of borage. To analyze the variance of the experimental data and drawing of diagrams, MSTAT-C 8 and Excel software was used. Means were compared according to Duncan multiple test at the 5% probability level.
Results and Discussion
Results showed that simple and interaction effects of irrigation level and plant density were significant on flower yield, seed yield, biological yield, flower number, branch number and seed number of borage. One thousand-seed yield affected significantly by different irrigation levels. These morphological changes in growth can be considered as a morphological adaptation of the medicinal plant to water and environmental stresses to decrease transpiration and to induce a lower consumption of water. The growth is the most important process that is affected by water stress and the decrease in the growth of cells leads to decrease the plant height and number of branches. The highest and the lowest flower yield were observed in I3D3 and I1D1 with 0.81 and 0.14 g.m-2, respectively. The maximum and the minimum flower number, biological yield and seed yield were recorded in D3I3 (with 69.60 flowrs.m-2, 592.07 g.m-2 and 29.57 g.m-2) and D1I1 (with 3.89 flowrs.m-2, 134.42 g.m-2 and 3.36 g.m-2) respectively.
According to the results obtained in the present study, the effects of irrigation levels and plant densities had significant effects on yield and yield components of borage. By increasing in irrigation level improved growth characteristics and yield, but by increasing in plat density up to 40 plants.m-2 declined its growth and yield due to inter species competition for water and nutrient absorption.
This research was funded by Vice Chancellor for Research of Ferdowsi University of Mashhad, which is hereby acknowledged.