Pattern of pyrethrin accumulation, achene and trichome development in relation to pattern of flower development in pyrethrum
Pyrethrum (Tanacetum cinerariifolium) is an economically important crop grown for extraction of a natural insecticide, pyrethrin, which accumulates in the achenes of the flowers. The process of pyrethrum flower development can be divided into eight developmental stages, depending on the opening of ray floret and disc floret whorls. This experiment was conducted to understand the pattern of pyrethrin accumulation and achene and trichome development in relation to the flower development process in pyrethrum. Plants were irrigated throughout the flowering period. The results of this experiment showed that the flower size, achene number, achene size and trichome density increased with increasing flower maturity and reached a maximum at physiological maturity. All these morphological characteristics decreased in magnitude at later flowering stages because of accelerated flower senescence. Pyrethrin yield also increased with increasing flower maturity, and reached a maximum at crop physiological maturity. Flower size, achene number, achene size, trichome number, and rate and duration of pyrethrin accumulation directly contribute to the final pyrethrin yield per flower. Examination of these patterns and relationships will be useful in explaining fluctuations in pyrethrin yield, as well as providing avenues to increase pyrethrin yield.
Suraweera, D.D., Groom, T. and Nicolas, M.E. (2017). Pattern of pyrethrin accumulation, achene and trichome development in relation to pattern of flower development in pyrethrum. Acta Hortic. 1169, 93-100
pyrethrin, achene, trichome, physiological maturity, flowering period