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Article

Stinging Trichomes in Apocynaceae and Their Evolution in Angiosperms

Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, SP, Brazil
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Academic Editor: Bartosz Jan Płachno
Plants 2021, 10(11), 2324; https://doi.org/10.3390/plants10112324
Received: 25 September 2021 / Revised: 21 October 2021 / Accepted: 21 October 2021 / Published: 28 October 2021
Stinging trichomes are rare in plants, occurring only in angiosperms, where they are reported for a few genera belonging to six families. Although there is no report of stinging trichomes in Apocynaceae, previous fieldwork collections of Fischeria and Matelea caused us a mild allergic reaction on the skin when we contacted the dense indumentum of the plants. This fact associated with the well-known presence of glandular trichomes with acute apex in both genera raised suspicions that stinging trichomes could be present in the family. Hence, this study aimed to investigate the likely occurrence of stinging trichomes in Fischeria and Matelea. We analyzed vegetative shoots and leaves of Fischeria stellata and Matelea denticulata through the usual procedures of light and scanning electron microscopy. We also performed several histochemical tests to investigate the chemical composition of trichome secretion. We detected that glandular trichomes occur throughout the surface of the leaf and stem. They are multicellular, uniseriate with an apical secretory cell, which has a dilated base and a needle-shaped apex. The secretion is compressed into the acuminate portion of the apical cell by a large vacuole, and crystals are deposited in the cell wall in a subapical position, providing a preferential site of rupture. The secretion, composed of amino acids and/or proteins, is released under mechanical action, causing skin irritation. Based on our detailed morphological and anatomical analyses, and in the functional aspects observed, we concluded that the glandular trichomes in Fischeria and Matelea can indeed be classified as stinging. Thus, Apocynaceae is the seventh family for which this type of trichome has been reported. We also compiled information on stinging trichomes in all families of angiosperms. Their phylogenetic distribution indicates that they have evolved at least 12 times during angiosperm evolution and may represent an evolutionary convergence of plant defense against herbivory. View Full-Text
Keywords: glandular trichomes; plant defense; evolutionary convergence; anatomy; secretion; Apocynaceae glandular trichomes; plant defense; evolutionary convergence; anatomy; secretion; Apocynaceae
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MDPI and ACS Style

Medina, M.C.; Sousa-Baena, M.S.; Capelli, N.d.V.; Koch, R.; Demarco, D. Stinging Trichomes in Apocynaceae and Their Evolution in Angiosperms. Plants 2021, 10, 2324. https://doi.org/10.3390/plants10112324

AMA Style

Medina MC, Sousa-Baena MS, Capelli NdV, Koch R, Demarco D. Stinging Trichomes in Apocynaceae and Their Evolution in Angiosperms. Plants. 2021; 10(11):2324. https://doi.org/10.3390/plants10112324

Chicago/Turabian Style

Medina, Maria C., Mariane S. Sousa-Baena, Natalie d.V. Capelli, Raquel Koch, and Diego Demarco. 2021. "Stinging Trichomes in Apocynaceae and Their Evolution in Angiosperms" Plants 10, no. 11: 2324. https://doi.org/10.3390/plants10112324

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