اثر کم آبیاری و تراکم بر رشد و عملکرد دانه و برخی صفات مورفولوژیک در گلرنگ )Carthamus tinctorius L(. پاییزه

Introduction
Vegetable oils such as safflower oil, due to high amounts of unsaturated fatty acids, play an important role in the fat balance of human diet and can reduce blood cholesterol level. Drought as the most important factor controlling the performance of the products, on a variety of factors that affect plant growth and yield (Ghamarnia and Sepehri, 2010). Although safflower is a drought resistant plant, but drought has significant effects on its duration of phenological stages, thus cause a significant reduction in yield, yield components, growth and some morphological traits such as plant height and distance to the first bifurcation branches from soil surface (Khoshnam et al. 2012). When the distance between plants in the row is low, vacancies are not green. Low density, especially in row plant spacing is not desirable. This experiment aims at identifying the critical stages of water and specifies the appropriate number of plants in conditions of stress and lack of tension in the area as well.
Material and Methods
In order to evaluate the effect of deficit irrigation and density on growth, seed yield and some morphological traits of a local variety of autumn safflower, an experiment was conducted with a spilt plot arrangement based on randomized complete block design with four replications at Research farm of Faculty of Agriculture, Birjand University in 2013-2014. Irrigation levels (complete irrigation, irrigation until flowering and irrigation until heading-bud stage) and plant density (20, 30, 40 and 50 plant per square meter) allocated randomly in main plots and subplots, respectively. Phonological aspects (number of days to emergence, stemming, heading bud, 50% flowering and physiological maturity) were recorded. The terms consisted of plant height, distance to the first bifurcation branches from soil surface and number of primary and secondary branches and seed yield. SAS ver. 9.1 statistical software was performed to measure the results of the analysis of variance (ANOVA) and means were compared with LSD test in 5% probability level.
Results Discussion
Results showed a significant reduction in plant growth period, plant height, distance to the first bifurcation branches from soil surface and number of primary and secondary branches in the irrigation until heading-bud treatment. The yield loss in this treatment was caused by early flowering and decrease in flowering period, seed filling period, maturity stage and yield components. It seems that the heading-bud stage is the most critical stage of the crop growing under water deficit conditions. Since all of the measured parameters had a positive correlation with seed yield, so a reduction of seed yield under the "irrigation until heading-bud treatment" is obvious. By increasing the plant density, plant height and distance to the first bifurcation branches from soil surface was increased but number of days until maturity and number of primary and secondary branches was reduced. In addition, the highest seed yield was obtained from full irrigation treatment with density of 40 plants in m2. In all plant densities, lowest seed yield was observed in the "irrigation until heading-bud" treatment. As it seems that this growth stage is the most susceptible stage of the crop to limited water, optimum irrigation in this stage may case a significant increase in seed yield.
Conclusion
According to the results of this experiment in order to achieve the maximum yield of safflower in Birjand region, full irrigation and density of 40 plant.m-2 is suggested. Supplementary irrigation during heading-bud stage is necessary to prevent a sharp drop in seed yield. The density of 40 plant.m-2 of safflower can cover the canopy faster and due to a reduction in soil evaporation, it can postpone the drought stress to the end of the growing season. This density, also with increasing the growing season, increasing the plant height and decreasing the number of low or non-fertile branches, results in better plant growth and thus helps to produce more seeds.


Materials and Methods In order to evaluate the effect of deficit irrigation and density on growth and seed yield and some morphological traits of autumn safflower (Mahali Isfahan, a local variety), an experiment was conducted in a spilt plot arrangement based on randomized complete block design with four replications at Research farm, Faculty of Agriculture, Birjand University in 2013-2014. Irrigation levels (perfect irrigation, irrigation until flowering and irrigation until heading-bud stage) and plant density (20, 30, 40 and 50) allocated in main plots and subplots, respectively. Phonological aspects (number of days to emergence, stemming, heading bud, 50% flowering physiological maturity) were recorded. The terms consisted of plant height, distance to the first bifurcation branches from soil surface and number of primary and secondary branches and seed yield. For statistical analysis, analysis of variance (ANOVA) and LSD test were performed using SAS ver. 9.1 software.

Results Discussion Results showed that a significant reduction in plant growth period, plant height, distance to the first bifurcation branches from soil surface and number of primary and secondary branches observed only in irrigation until heading-bud treatment. This treatment caused yield loss via early flowering decrease in flowering period, seed filling period and maturity stage and components yield. It seems that it is one of the most critical stages of the growing crop under drought conditions. As regards all of the measured parameters had a positive correlation with seed yield, as a result, reduction of seed yield under irrigation until heading bud treatment obviously. When plant density increased, plant height and distance to the first bifurcation branches from soil surface was increased but number of days until maturity and number of primary and secondary branches was reduced. In addition, the highest seed yield obtained in treatment of full irrigation with density of 40 plants in m2. In all densities, lowest seed yield observed in irrigation until heading-bud treatment. It seems that this growth stage is most susceptible stage to limited water and under this conditions with irrigated in this stage we can increase significantly seed yield.

Conclusion According to the results of this experiment in order to achieve maximum yield of safflower in Birjand region, full irrigation and plant density with 40 plant m-2, is suggested. It is necessary to the use of supplemental irrigation during heading bud stage to prevent a sharp drop in seed yield. At the beginning of the growth season, plant density with 40 plant m-2, with a faster cover due to reduce the influence of sunlight on the surface of the soil and reduces evaporation from it. Therefore it delays drought stress at plants this density. Also this density with the advance of the growing season, through increased plant height and decreased number of low or non-fertility branches results in better plant growth and thus helps to produce more seeds.

Keywords: drought stress, plant distance in row, developmental stage, seed yield, oil seed

References

• Sirus Mehr, A.R., Shakiba, M.R., Alyari, H., Tourchi, M., and Dabagh Mohammadi Nasab, A. 2008. Effect of drought stress and density on yield and some morphological characteristics of autumn safflower cultivars. Research in Agronomy and Horticulture.78:80-87. (In Persian with English abstract).
• Khoshnam, A., Haydari Sharifabad, H., Afsharmanesh, G.R. 2012. Effects of terminal water deficit stress and plant density on yield, yield components and some morphological traits of safflower in Jiroft Region, Iran. Plant Ecophysiology, 4: 111-117.
• Ghamarnia, H., and Sepehri, S. 2010. Different irrigation regimes affect water use, yield and other yield components of safflower (Carthamus tinctorius L.) crop in a semi-arid region of Iran. Journal of Food, Agriculture & Environment, 8(2): 590 - 593.