Flower nettle family

Flower nettle plants (Loasaceae) are almost exclusively native to the tropics and subtropics of the Americas. The systematics and evolution of the plants are being researched.

Beautiful flowers - but dangerous

The flower nettles have - as their name suggests - very beautiful flowers, but, unfortunately, a lot of stinging hairs. This is certainly the reason why they are hardly grown in parks and gardens.

For animals, any attempt to eat the pretty flower nettle will end painfully. As soon as the tongue touches the stinging hairs, they inject a hurtful mixture into the animal's mouth.

A total of five plant groups have developed stinging hairs, completely independently of each other. The stinging hairs have a sideways-pointing head at their tip. When touched, the head breaks off, forming an sharp point - like the needle of a syringe. The irritating substances are forced from the hairs into the skin by pressure.

Flower nettle Cajophora chuquitensis © W. Lobin / Universität Bonn
Loasa pallida - Pale flower nettle from central Chile, Andes © Botanische Gärten der Universität Bonn

Stinging nettles have hairs which are stiffened with silicon. The flower nettles, on the other hand, use calcium phosphate to harden their stinging hairs. This is a nutrient found in humans´ and animals´ teeth and bones. Previously, plants were not known to use calcium to build their cell walls.

Stinging and hook hairs of the flower nettle Loasa pallida under the scanning electron microscope. The strong mineralization of the entire stinging hairs (dark red) and the head-shaped tip is clearly visible. © Botanische Gärten der Universität Bonn

The main component of the cell walls, the fibrous cellulose, forms a shaping mesh in which tiny crystals of calcium phosphate are embedded. This gives the stinging hairs extraordinary stability. It is still a mystery why the flower nettles have chosen this exceptional path.

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