There is likely far more trichomes on your plants than you believe, but also it is likely that they are not the type of trichomes you want in the locations you want them or in the numbers you want them
3.5.1.2 Cystolythic trichomes
This type of trichome is shown in Figure 3.3b. Specimens were first observed on the upper surface of the initial pair of true leaves on a cannabis seedling. Always pointing towards the distal part of the leaf, these trichomes gave the upper surface a texture that was rough to the touch.
At the base of each trichome is a cystolyth. These concretions are common throughout the plant kingdom and are typically formed from calcium oxalate or calcium carbonate crystals. Those found in Cannabis are of the latter type (Dayanandan and Kaufman, 1976; Evans, 2002). These tough trichomes would presumably reduce the palatability of the foliage to leaf-eating predators. Histochemical chemical staining of these trichomes with fast blue occasionally resulted in pigmentation of these organelles, but the presence of phenolic substances on these trichomes was attributed to contamination from leaking capitate stalked trichomes. This supposition was supported when the vital stain tetrazolium red was used. No reduction of tetrazolium was observed apart from in the cells immediately surrounding the cystolyth, where respirative activities accompanied the formation of these concretions.
Figure 3.3. (a) Unicellular non-glandular trichome. The sample is temporarily mounted under hemp oil and viewed in transmitted light; (b) Cystolythic trichomes observed on the leaf margin of a young leaf. The sample was temporarily dry-mounted and viewed in transmitted light. Cystolyths (concretions of calcium carbonate) are visible at the base of each trichome (Potter, D..J.).
Chapter 3. Cannabis trichome form, function, and distribution
3.5.1.3 Capitate sessile trichomes (more commonly simply called sessile trichomes)
Figure 3.4. (a) a capitate sessile trichome observed on the edge of one of the first pair of true leaves of a cannabis seedling. The specimen was temporarily dry-mounted and viewed using both transmitted and incident light; (b) a sessile trichome on a leaf surface stained with Fast Blue. The still-wet sample was temporarily dry-mounted and viewed using incident light (Potter, D..J.).
Apart from on the cotyledons and the supporting hypocotyl, sessile trichomes were observed on all other aerial surfaces throughout the plant’s lifespan. The example shown in Figure 3.4a was a very rare find, being situated on the margin of one of the first pair of monofilous leaves of a cannabis seedling. This location enabled the specimen to be observed in profile, without the need of microtome sectioning.
Those previously studying cannabis trichomes have referred to this type as sessile (Latin sessilis – sitting) or capitate sessile (Latin caput – head). By definition this type does not have a stalk. The trichome is in fact connected to the mesophyl cells via a stalk cell, but this is hidden beneath the trichome resin head. The stalk cell was seen to contain chloroplasts, enabling some photosynthetic activity. This form of trichome is found in many other plant families and, due to its flattened shape and short stalk, is often referred to as a ‘peltate’ trichome (Latin pelta – a short-handled hand-held round shield). According to some plant physiologists, the development of this structure from sub-epidermal cells defines this structure as an ‘emergence’ rather than a ‘trichome’ – the latter always developing from an epidermal cell. However, as stated earlier, most authors regard both structures as ‘trichomes’ (Werker, 2000).