Determining trichome elemental composition in Solanum wild and domesticated species using SEM-EDS

Trichomes are specialised epidermal structures on plant surfaces of plant aerial organs. They are integral to plant defence and adaptation. However, their elemental composition in Solanum species remains understudied. This research investigates the elemental composition of trichomes from five Solanum species, including representatives of the crops tomato and potato - Solanum berthaultii, Solanum galapagense, Solanum lycopersicum (tomato), Solanum pennellii, and Solanum tuberosum (potato) - using herbarium samples from the Royal Botanic Gardens, Kew. Samples were carbon coated and observed under the Field Emission Gun Scanning Electron Microscopy (FEG SEM). Energy Dispersive X-ray Spectroscopy (EDX/EDS) data were collected using an EDX detector. Results revealed significant variation in elemental content among the five Solanum species. The trichomes of S. berthaultii showed high levels of potassium (K), especially at the tips, suggesting a role in osmoregulation and defence. S. galapagense exhibited notable chlorine (Cl) and calcium (Ca) presence, possibly for ionic balance and pest deterrence. S. lycopersicum and S. pennellii had higher silicon (Si) concentrations in the mid-sections and tips of the trichomes, enhancing structural integrity and herbivory resistance. S. tuberosum displayed significant variability in calcium (Ca), particularly at the base, in which could be of importance for maintaining cellular structure and for rapid damage response. This study provides insights into the elemental composition of the trichomes of Solanum species, contributing to our understanding of their ecological and physiological roles. Our findings underscore the importance of elemental composition in studies of plant adaptation and evolution, offering a foundation for future research in plant defence mechanisms and environmental interactions.