The Implication of Phenolic Acids in the Development of Prickles from the Glandular Trichomes of Raspberries, Roses, and Rose Hips

Many plants in the genus Rubus share the development of prickles. During prickle development a glandular trichome forms a stalk connecting a glandular head to the rest of the plant.  This structure stores phenolics, which are secondary metabolites used in in plants for a wide variety of functions. Evidence suggests phenolic are sent as signals from the trichome head down the rest of the stalk, stimulating cellular divison that results in a fully formed prickle. We tested the hypothesis that if trichome heads are removed, signals from phenolics will no longer be sent and continuation of development will fail. We used diphenylboric acid 2-aminoethyl ester (DPBA) to stain phenolics in prickles of roses, raspberries and rose hips, tracking their movement under a fluorescence microscope. Length of the trichomes and distances phenolics traveled down the prickle were measured in normal prickles and prickles with glandular heads removed. We found phenolics travel from the trichome head down the stalk of the prickle to the rest of the plant causing cell proliferation. Additionally, when trichome heads were removed signals were no longer sent to the plant and cell proliferation is reduced. Our results suggest phenolics are sent as signals from glandular heads down the stalk of the trichome and play a role in prickle development.