Investigation of the effect of planting density and supplementary irrigation on response of photosynthetic pigments and catalase and ascorbate peroxidase and forage yield of two safflower cultivars (Carthamus tinctorius L.)

Due to the high resistance of safflower to environmental severe conditions, many researchers use this plant as a model to explore and understand the defense mechanisms against environmental stresses. In this regard, an experiment was carried out to investigate the reaction of photosynthetic pigments and catalase and ascorbate peroxidase in planting density of two safflower cultivars under supplementary irrigation conditions at the farm of Faculty of Agriculture, Ilam University. The experiment was conducted in a split- plot design with factorial arrangement. The treatments which included the main factor of irrigation at two levels (supplementary irrigation and dry-land) and sub -factors, including density at five levels (20, 30, 40, 50 and 60 kg/ha) and two cultivars (Goldasht and Faraman) were performed with three replications. The results of evaluation of these traits showed that the highest total chlorophyll content (a and b) occurred in supplementary irrigation treatment, and carotenoid content was not affected by any of the treatments. When density increased, anthocyanin level increased, but the highest density was observed at 40 (kg ha-1). Similarly, Faraman cultivar had better performance in terms of anthocyanin than Goldasht. Flavonoids, also, augmented when planting density increased. Catalase enzyme had better performance in dry-land treatment, and both catalase and ascorbate peroxidase increased with the increase of planting density, which improved the adaptability and drought tolerance in semi-arid areas (the area where the experiment was conducted) for this product.