Changes in some biochemical characteristics of purple coneflower (Echinacea purpurea (L.) Moench) medicinal plant in response to planting date and soil flooding duration

This research was aimed to investigate the effect of planting date and soil flooding duration on some biochemical characteristics of purple coneflower (Echinacea purpurea (L.) Moench) in Sari region. The study was conducted in a RCBD based split plot with three replications in the Research Farm of the Genetics and Agricultural Biotechnology Institute of Tabarestan، Sari Agricultural Sciences and Natural Resources University، in 2012. Experimental treatments included three planting dates (June 30، July 30 and August 29) and three soil flooding durations (without flooding as control، three and five-day flooding) which were considered as main and sub-plots، respectively. Malondialdehyde (MDA)، total phenols and flavonoids contents، protein oxidation of the leaves، enzyme activities of superoxide dismutase (SOD)، ascorbate peroxidase (APX)، peroxidase (POD) and catalase (CAT)، as well as percentage of DPPH free radical inhibition were determined. Results of this experiment showed a significant increment of malondialdehyde (MDA) content in purple coneflower leaf with the highest level in five-day flooding duration and in August 29 planting date. The highest decrease in total protein was found in the same planting data and flooding duration with 90 % decline than control. The highest activity of antioxidant enzymes of superoxide dismutase (SOD) and ascorbate peroxidase (APX) was recorded in the purple coneflowers leaves، cultivated in June 30، and flooded for three days، while the highest activity of peroxidase (POD) and catalase (CAT) were observed in plants cultivated in July 30. Five-day soil flooding markedly increased the total phenols and flavonoids content just in plants transplanted in June 30. In addition، the highest percentage of DPPH free radical inhibition was measured in plants subjected to continues five-day soil flooding and cultivated in August 29. In conclusion، it seems that the coneflower plant relatively showed a good tolerance to flooding stress.