Taxonomy & Evolution

Morphological characterisation of trichomes

Can we use electron microscopy and statistical analyses to better classify the trichomes of the large plant genus Solanum?
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Plant surfaces show spectacular variation in the shape, size, location, function and origin of epidermal projections. The most important and well-studied among these are trichomes, hair-like structures that can originate from the epidermis of leaves, stems, flowers and fruit. Trichomes are distributed almost universally in the plant kingdom and exhibit dramatic variation in their morphology. They can be unicellular or multicellular, glandular or non-glandular, conical to elongated, smooth to grooved, thin to thick-walled, the list could go on. Functionally, trichomes are generally considered as one of the first lines of defence possessed by plants to protect against biotic and abiotic stress, including harmful UV, drought, temperature extremities and herbivore damage.

The trichomes of the Solanum genus are incredibly diverse, however, until now they not been characterised properly. Image credit: Watts & Kariyat.

Solanum is the largest genus of the Solanaceae family with approximately 3500 species of ecological and economic importance. The genus has a diverse set of trichomes that vary in density and morphology. However, due to an incomplete and contradictory classification system, Solanum trichomes have subjective names and have been largely limited to being grouped into just glandular or non-glandular types. A better classification system based on the diverse morphology of trichomes within this genera has long been required by botanists and taxonomists.

In their new study published in AoBP, Watts & Kariyat comprehensively document the morphological variation of trichomes on the leaves of 14 Solanum species. Using a mixture of wild and cultivated species, their study aims to catalogue the major trichome types in the Solanum genus. The authors used electron microscopy, statistical analyses and artistic renditions to examine extremely fine details of trichomes and measured their density and dimensions to compile a detailed data set which can be of use for estimating the variation in trichome types. Their study is the first of its kind, providing us with a better and well-defined classification, density and dimension analysis for the morphological classification of trichomes on both leaf surfaces of a diverse range of Solanum species.


Watts, S. and Kariyat, R. (2021) “Morphological characterization of trichomes shows enormous variation in shape, density and dimensions across the leaves of 14 Solanum species,” AoB PLANTS.

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