A physical method is described for the rapid isolation of plant trichomes, with emphasis on stalked glandular types. The technique involved breaking frozen trichomes with powdered dry ice and collection of glandular heads by sieving from larger tissue fragments. This method was applied to several plants that bear similar stalked trichomes: geranium (Pelargonium), potato (Solanum tuberosum), tomato (Lycopersicon esculentum), squash (Cucurbita pepo), and velvetleaf (Abutilon theophrasti). The tissue preparation was of sufficient quality without further purification for biochemical and molecular studies. The preparation maintained the biochemical integrity of the trichomes for active enzymes and usable nucleic acids. A large quantity of tissue can be harvested; for example, 351 milligrams dry weight of glandular trichomes were harvested from geranium pedicels in 12 hours. The utility of the technique was demonstrated by examining the fatty acid composition of tall glandular trichomes of geraniums, Pelargonium xhortorum L.H. Bailey. These purified cells contained high concentrations of unusual omega5-unsaturated fatty acids, proportionally 23.4% of total fatty acids in the trichomes. When the trichomes were removed, the supporting tissue contained no omega5-fatty acids, thereby unequivocally localizing omega5-fatty acids to the trichomes. Because omega5-fatty acids are unique precursors for the biosynthesis of omega5-anacardic acids, we conclude that anacardic acid synthesis must occur in the glandular trichomes.
