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Lavender leaf

Annie Cavanagh and David McCarthy

Download this image from Wellcome Collection.

This false-coloured scanning electron micrograph (SEM) shows a lavender leaf (Lavandula) imaged at 200 microns. Lavender, which is native to the Mediterranean region, is an evergreen shrub that grows to about three feet high and has small blue or purple flowers and narrow grey leaves. Lavender yields an essential oil with sweet overtones, which can be used in balms, salves, perfumes, cosmetics and topical applications. It is also used to aid sleep, to relax and to alleviate anxiety.

What are the spiky structures on the leaf surface?

The surface of the leaf is densely covered with fine hair-like outgrowths made from specialised epidermal cells called non-glandular trichomes, which are found on a wide variety of plant species. The hairs keep frost away from the surface cells and break up the flow of air across the leaf surface, reducing evaporation. Dense coatings of trichomes also reflect solar radiation, protecting the delicate tissue beneath. In habitats where plants rely on their supply of water from cloud drip, trichomes have been found to enhance this collection process. In addition, trichomes protect the plant against pests because the hairs interfere with their feeding process. Glandular trichomes, which contain volatile oils and other secretions that are produced by the plants, are also present on the surface of the leaf.

Why did the judges like this image?

Alice Roberts (anatomist, author and TV presenter) explains: "This gorgeous, extreme close-up of the surface of a lavender leaf, viewed through a scanning electron microscope, clearly shows the bulging droplets of oil that provide the plant with its heady scent. Artificial colour has been used brilliantly here, to pick out the salient details, but also gives the image a startling Avatar-like quality."