Journal of Plant Process and Function

To find out the effect of planting date and planting density on antioxidant capacity, phenolic compounds, yield dry matter and characteristics of medicinal plant purple coneflower root, a randomized complete block design in split plot arrangement with three replications was conducted in Research Farm of Sari Agricultural Sciences and Natural Resources University in 2012-2013. Experimental treatments included three planting dates (April 9, May 9 and June 8 2013) and three planting density (7, 10 and 16 plant/m2). Measurements were performed in full bloom stage. Results of experiment showed a significant increment of penetration depth of root in 9 may with a density of 16 plant/m2. The highest root volume and dry matter were related to 8 June and 7 plant/m2. However, the highest total dry matter (130.5 g/plant) was related to the purple conflowers that planted on 9 April with 10 plant/m2. Plants grown on 8 June with a density of 7 plant/m2 resulted to the highest ratio of dry matter root to total and root to shoot. The highest cichoric acid (19.5 mg/ g dry matter) and total phenol (30.8 mg of GAE/ g dry matter) content of root were observed in plants grown in 9 May with a density of 16 plant/m2. The highest amount of total flavoneid and antioxidant capacity of root were measured in coneflower plants that planed in 8 June with a density of 16 plant/m2. In conclusion, it seems that late planting date 8 June in this experiment conditions is suitable for more root dry matter, total flavoneid and antioxidant capacity, while planting date 9 May is suitable for more cichoric acid and phenollic content in the root of the coneflower plants. In addition to, low density of 7 plant/m2 resulted in increase in root dry matter and decrease in cichoric acid and total phenol content as well as antioxidant capacity in coneflower roots.