Non-glandular trichomes (epidermal hairs) in cannabis ( Cannabis sativa L.) plants are capable of excreting nutrient salts under excessive fertilizer regimes

Symptoms of leaf spots and blighting resembling pathogen infection were observed on the foliage of Cannabis sativa L. plants grown hydroponically. Symptomatic tissues were subjected to whole genome sequencing and polymerase chain reaction with fungal-specific primers to determine if a microbe was responsible for the symptoms. Neither method revealed a potential fungal or bacterial pathogen. Light and scanning electron microscopic studies of affected tissues revealed the consistent presence of a white powdery crystalline material. X-ray microanalysis confirmed the crystals contained calcium, sodium, and several other cations, as well as chloride. The salts were extruded directly from the tips and walls non-glandular trichomes (hairs) present on stems and leaves. Following extrusion through the tips and walls, the salts aggregated around the base of the trichomes, forming white crystalline patches, particularly along leaf veins and on stems. Treatment of plants with excess levels of nutrient salts produced similar symptoms. The ability of non-glandular trichomes of C. sativa to extrude nutrient salts under conditions of excessive fertilizer regimes is described for the first time. The potential roles of these trichomes in transporting salts out of plants exposed to toxic levels of nutrients in the environment and in enhancing salt tolerance warrant further investigation.