Tomatoes, potatoes and deadly belladonna all belong to one plant family
The nightshade family gives the world some of its favourite foods, including tomatoes, potatoes and chilli peppers, alongside tobacco and Atropa belladonna, among the most toxic plants anywhere. The link is chemistry: many of its roughly 2,700 species pack high levels of alkaloids, which can nourish, stimulate, soothe or kill.
Solanaceae arose in South America and, after the mass extinction that ended the age of dinosaurs, diversified rapidly. Today nightshades grow on every continent except Antarctica, in deserts, tundra, rainforests, plains and highlands, as trees, shrubs, vines and even plants perched on other plants. Nearly 80 per cent of species fall in the subfamily Solanoideae, most of them in the genus Solanum, though the family's internal classification remains contested.
Their alkaloids explain much of their fame. Nicotine made tobacco a recreational drug for centuries. Tropanes in belladonna can relieve pain, relax or cause hallucinations, which keeps the plant popular in alternative medicine despite its danger. Capsaicin gives Capsicum fruits their bite and underlies most of the spicy food sold today. Other members are grown for looks, such as the long trumpet flowers of Brugmansia and the many colours of petunias.
Both names are puzzles. Solanum may come from the Latin sol, sun, perhaps because some flowers resemble a rayed sun, and one species is even called sunberry; or it may derive from solare, to soothe, a nod to the calming effects of psychoactive species. Nightshade traces to Old English nihtscada, shade of night, with German and Dutch cousins, but nobody knows why, possibly because of how the fruits look.
Genetics shows a tidy pattern. Most species carry 24 chromosomes, and others hold higher multiples of 12. Around 200 wild potato species range from two to six sets, while the cultivated potato has 48 chromosomes, four sets of 12. Scientific interest dates to 1763, when the French naturalist Michel Adanson grouped ten genera as Les Solanum. Antoine Laurent de Jussieu gave the group its formal name in 1789, and Solanaceae became the standard name by 1905.
Source: Solanaceae
