Abstract

The effect of spray application of two plant growth retardants (cycocel and daminozide) on the growth, flowering and amount of essential oils of Calendula officinalis L. was investigated. Combinations of cycocel (CCC) (0, 500, 1000 and 1500 mg/L) and daminozide (B9) (0, 1500, 3000, and 4500 mg/L) was used three times. Plant height, number of flowers per plant, number of leaves per plant, flower dry weight, flower fresh weight, time of flowering and the amount of essential oils per 100 g dried flower were measured. Results showed that the effect of CCC and B9 were significant on the amount of essential oils per 100 g dried flower and plant height (p≤0.01). Also, interaction effects of CCC and B9 were significant on plant height, the number of flowers per plant, number of leaves per plant, flower dry weight and the amount of essential oils per 100 g dried flower. The lowest plant height (30.67 cm), the largest number of flowers per plant (3.33), the highest number of leaves (6.67), and the highest amount of essential oils per 100 g dried flower (0.159 mL) were observed in 500 mg/L CCC + 4500 mg/L B9, 500 mg/L CCC + 1500 mg/L B-9, 500 mg/L CCC + 1500 mg/L B9 and 1500 mg/L CCC + 1500 mg/L B9, respectively.

Key words: Calendula officinalis L., plant growth retardant, growth and flowering traits, essential oils, plant height.