Cannabis trichomes help push out nutrient salts, metal ions

Life invents new tricks when exposed to stress. Plants, for example, develop toxins and physical defenses to defend against the stress of hungry predators. One idea suggests that certain classes of vascular plants developed small external features, known as trichomes, to deter herbivores from consuming them. Special salt-tolerant plants use the structures like pores that excrete excessive nutrient salts. Professor Zamir Punja proved for the first time that cannabis excretes nutrient buildup from its non-glandular trichomes.

Cannabinoids are produced in glandular trichomes, a key research topic for cultivators and processors. Leaf hairs are a form of non-glandular trichome found on vegetative plants. We focus on them less because they cannot produce cannabinoids or terpenes. Leaf hairs can protect a plant from herbivores and UV rays, or help sweat out excessive salts.

Symptoms without infection

A study published in the scientific journal Botany examined cannabis plants with leaf spots. While symptoms noted in the paper were typically synonymous with infection. A high-THC strain that expressed symptoms tested negative for pathogenic DNA that would cause the noted symptoms. A white crystalline salt built up was visible on the stems of overfed plants.

Punja observed plants that had been rooted in rockwool and grown in cocofibre in a licensed greenhouse. Symptoms began to appear three to four weeks after the plants were moved into a flowering cycle. At this stage, several specimens of one particular genotype started expressing symptoms described by the author as, “wilting, with newly developing shoots dying back and leaves turning necrotic. Leaves developed visible spots that began at the margins and coalesced to form larger necrotic areas.”

Salt deposits

Punja reported that the necrotic spots looked like leaf blight. Moreover, the white crystalline powder formed along leaf veins in areas showing necrosis. The author exposed leaf samples to a concentrated fertilizer solution. Results suggest that noteworthy symptoms were the result of nutrient salt burn. Professor Zamir Punja also observed his samples of non-infectious plants with an electron microscope.

Non-glandular leaf hairs are abundant on the underside of newly developed leaves, especially close to the center. Necrosis was synonymous with nutrient buildup, which occurred in locations with a high trichome density. Sessile trichomes are found interspersed with non-glandular hairs. Scans from the electron microscope captured the latter pushing out a stringy secretion from their tips and stalks. Secretions would occasionally coil into a three-dimensional structure.

A halophyte?

Microanalysis of the three-dimensional structures determined that trichomes excrete varying levels of calcium, potassium, and chloride. Magnesium and sulfur were also present, and one sample contained silicon. Cocofiber samples contained nutrients like copper and manganese that were not observed in trichome secretions. Plants showing symptoms were fed more nitrate-N, potassium, calcium, sulfur, boron, sodium, and chloride.

Punja noted that cannabis does not fit the definition of a halophyte. These are the only plants capable of excreting salt from non-glandular trichomes. While the effect might be genotypic, cannabis continues to prove its resilience as a hyper-accumulator.

Sources

1. Zamir K. Punja. 2026. Non-glandular trichomes (epidermal hairs) in cannabis (Cannabis sativa L.) plants are capable of excreting nutrient salts under excessive fertilizer regimes. Botany. 104: 1-25.