A complex story of trichome types and chemistry in Cannabis vegetative and reproductive organs

Abstract Cannabis sativa trichomes produce hundreds of therapeutic compounds. However, progress in understanding trichome function and chemistry has been hindered by the absence of a unified and consistently applied trichome nomenclature, as well as by limited characterization of trichome diversity, organ-specific distribution, and their relationship to organ chemotype. In this study, we examined the trichome features of different organs in unfertilized female plants of the medical cannabis cultivar ‘NB120’ using light and electron microscopy, energy-dispersive X-ray spectroscopy (EDX) to assess trichome biomineralization, and chemical analyses of THC and CBD content. All investigated organs exhibited defensive pointed non-glandular trichomes and several types of glandular trichomes. Vegetative fan leaves additionally displayed cystolithic trichomes on the upper leaf side, and completely lacked long-stalked glandular trichomes. The flowers and the margins of inflorescence leaves were densely covered with long-stalked glandular trichomes. THC and CBD concentrations were highest in the flowers, about 50% lower in inflorescence leaves (sugar leaves) and considerably lower in fan leaves. Pointed non-glandular trichomes on the flower bracts, particularly abundant on apical parts and margins, were biomineralized with calcium and silicon. Based on these observations, we propose a simple and practical classification framework comprising four readily distinguishable trichome types: two glandular (capitate and bulbous) and two non-glandular (cystolith and pointed) - to facilitate consistency and integration across studies. Together, our results highlight cannabis trichomes as a complex system of chemical and mechanical defenses and demonstrate that organ-specific distribution of long-stalked glandular trichomes is closely associated with cannabinoid content - indicating that trichome-type distribution profiles may serve as indicators of chemotype and, consequently, of medical and commercial value.