Floral Morphology of Artemisia annua with Special Reference to Trichomes

Floral morphology of Artemisia annua L. was described using light and scanning electron microscopy. Floral trichomes include nonglandular T-shaped filamentous trichomes, which occur on the basal bracts and pedicel of the capitulum, and 10-celled biseriate glandular trichomes on receptacle and bracts of capitula and corolla of florets. The heart-shaped biseriate glandular trichomes, composed of two columns of five cells each, are similar to those described for the leaf. During floral development, the cuticle surrounding the apical cells of biseriate glands detaches and forms a saclike reservoir for fluids excreted by the apical cells. The cuticle ruptures at anthesis, discharging its contents on the inflorescence. Artemisinin was detected by HPLC-EC from flowering branches dipped for 60 s in petroleum ether or acetonitrile, providing corroborating evidence that biseriate glandular trichomes were the likely site of artemisinin sequestration.