A multivariate analysis of morphological divergence of “seeds” (achenes) among ruderal, fibre, oilseed, dioecious/monoecious and marijuana variants of Cannabis sativa L.

Abstract

Cannabis sativa has been domesticated for stem fibre and oilseed (the two classes are both low in the euphoric cannabinoid THC and called “hemp”), and marijuana (high in THC), and also occurs as weedy, ruderal plants. Achenes (“seeds”) from herbarium collections representative of these classes were assessed for morphological characters and pericarp resistance to fracture. In contrast to ruderal plants, domesticated plants (both hemp and marijuana) possessed achenes that were significantly longer, heavier, covered with a less adherent perianth, and lacking a pronounced basal attenuation. All of these characteristics reflect traits that are advantageous in domesticated plants and are consistent with the “domestication syndrome” found in propagules of other crops. Marijuana achenes, in comparison with hemp achenes, tended to be about 26% shorter and about 32 shades darker (on a 256-bit grayscale). Achenes of fibre cultivars proved to be about 19% longer than the achenes of oilseed cultivars. Achenes of dioecious oilseed cultivars proved to be about 6% longer than the achenes of monoecious oilseed cultivars. The pericarps of hemp seeds were about 26% and about 15% more resistant to fracture than those of ruderal and marijuana plants, respectively.