Effect of spraying with gibberellin on the growth, flowering and chemical content of Calendula officinalis L.

Abstract

The study was conducted in one of the greenhouses of the Department of Horticulture and Landscaping, College of Agriculture and Forestry, University of Mosul, for the period from September 15, 2022, to June 1, 2023, on the pot Marigold plant Calendula officinalis L. cv. Pacific Beauty, in yellow and orange colors, with the aim of this study is the effect of spraying gibberellin at conc. (0, 200, 300 mg L^-1) conducted with a randomized complete block design (R.C. B. D.) was used. Spraying treatment with gibberellin at a concentration of 300 mg L^-1 resulted in a significant increase in plant height 49.04 cm and plant spread 29.46 cm compared to the control treatment and the total chlorophyll content showed significant differences. As for the flowering growth traits, it was noted that the least number of days for the first inflorescence to open was when spraying gibberellin at a concentration of 200 and 300 mg L^-1, and reached 66.67 and 79.67 days, respectively, while the largest diameter of the first inflorescence reached 58.58 mm, which was significantly excelled on the two treatments sprayed with gibberellin. While it was observed from the traits of the seeds and the content of carotenoids, it is noted from the table that the treatment of not spraying with gibberellin gave the highest values in the two traits of the number of total seeds and the total seed yield of 452.29 seeds. plant^-1 and 1.88 g. plant^-1, respectively, and it significantly excelled in the treatments spraying with gibberellin. While the traits of the content of carotenoids (alpha and beta) in the inflorescences did not show any significant differences between the treatments when sprayed with gibberellin or not, the highest values of alpha-carotene for yellow and orange inflorescences were for the treatment without spraying with gibberellin and reached 392.54 and 397.2 μg L^-1, respectively.