Saturday, July 9, 2011

Nightshades: Deadly and Delicious

This week on the farm, I harvested tomatoes, specifically orange cherry tomatoes.  We are just tipping over the edge of the top of the tomato waterfall on the farm.  Soon we'll be picking bucket after delicious bucket in a rush to keep up.

The orange cherry tomato fruits look remarkably like the fruits of one of our most poisonous local weeds, the horse nettle.  I can attest, from eating several tomatoes as I harvested, that the cherry tomatoes are delicious and non-toxic.  Here are pictures of both fruits:

Orange Cherry Tomatoes, picture source.

Horse Nettle Berries, picture source.
These two plants are actually close relatives on the evolutionary tree.  They are both in the plant family called the Nightshades, or more scientifically, the Solanaceae.  They don't belong to the same genus, (Lycopersicon esculentum for tomatoes, and Solanum carolinense for the horse nettle), but they have a surprising number of traits in common.  All members of the Solanaceae have flowers with 4-5 petals, alternate leaves, radially symmetrical flowers, and fruits that are technically berries or capsules. Both of our featured plants today have flowers with 5 petals that radiate our like little stars.  Tomato flower petals are usually yellow, whereas horse nettle flowers are light purple, but otherwise the flowers are nearly identical.  They both have fruits that are berries, meaning they are produced from one ovary and have a fleshy interior.  (As you might suspect, the botanical term berry is different than the grocery store term.  Strawberries and raspberries are not berries, watermelons and bananas are.  Don't worry about it.)  Cherry tomato and horse nettle berries are virtually identical inside and out, at least upon visual inspection.  Our two plants also have similar leaves and similar overall growth forms.

Tomato flowers, source.

Horse nettle flowers, source.
These two plants reenact the history of the Solanaceae as it affects humans - the question of whether a nightshade will nourish or kill.  The Solanaceae has no doubt been responsible for many of both outcomes.  It is a major plant family, with many species of major importance to humans.  The list of nourishing nightshades is impressive: tomatoes, garden peppers and hot peppers, potatoes, eggplants, tomatillo and more.  The poisonous nightshades include tobacco, potato (the greed parts), Jimson weed, belladonna (also called deadly nightshade), and mandrake. 

Considerable prejudice against the Solanaceae built up in Europe, as most native nightshades are highly toxic.  Our edible nightshades originated mostly in the New World.  As tempting as it is to think of tomatoes as Italian and potatoes as Irish, these plants were imports to Europe after they were 'discovered' by European explorers.  At first, Europeans were hesitant to eat the imported nightshades, but soon they incorporated them seamlessly into their cuisine.  Remnants of nightshade phobia exist today, with some people avoiding them altogether.  It is possible to be allergic to nightshades, which makes navigation of modern American cuisine very difficult - no French fries, no tomatoes, no hot sauce!

Toxic nightshades have a rainbow of alkaloids.  Mandrakes and Jimson weed are grimly hallucinogenic in smaller doses and toxic in larger doses.  Tobacco is addictive and stimulant, and the number one killer in the United States.  Belladonna is likely the most acutely toxic plant of the Western Hemisphere, with only a few of the sweet-tasting berries necessary to kill a person.  It has been used to make poison-tipped arrows.  The alkaloids in these poisonous plants can be useful to medicine.  For example, atropine, discovered in belladonna, is used to make the substance that dilates eyes in eye exams, to speed up the heart, and to counteract some pesticide poisonings.   

1 comment:

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