In The Botany of Desire, Michael Pollan espouses a new way of thinking about plants: that the plants we use are also using us. Crop plants have found a way to survive the human onslaught by serving us, by bending to our desire for bigger fruit, and their reward for their obedience is that we propagate them, rid them of weeds, give them huge tracts of land, and basically wait on them hand and foot. (Leaf and root?) Today, I’d like to talk about one of the most manipulative plants out there, and one dear to both my heart and my lungs: tobacco. Because tobacco, more than just figuring out how to found an entire country devoted to its propagation despite having no nutritive value whatsoever, doesn’t just manipulate humans. It manipulates insects. And in learning about how it does that, you might begin to see what I’ve been saying about beings “communicating” with each other.
Tobacco is a talker.
Of course, domesticated tobacco, like most domesticated things, has been dumbed down. We’re talking about its wild ancestor, Nicotiana attenuata, or coyote tobacco. And aptly named, because it’s pretty wiley. Tobacco’s main defense is nicotine; the stuff that lights up your brain after a beer is the same stuff that makes a bug dance the jig of death. It’s an insecticide. When one of the plant’s natural enemies — let’s say a hawkmoth caterpillar — starts chowing down on it, its first reaction is to up its nicotine levels. But if that doesn’t deter the caterpillar, it takes a different tack: it summons the dragon. It sends a chemical signal into the air that attracts a parasitic wasp that preys specifically on that caterpillar. The tobacco cries out — something between “HELP!” and “YO, FREE BUFFET, OVER HERE!” — and the wasp comes out of the sky and obliterates the caterpillar by laying eggs in its body, which quickly hatch into larvae which eat their host from the inside out.
What’s even more ingenious is that tobacco can recognize which of its enemies is attacking it (by “reading” the saliva), and send out a particular signal that will attract that enemy’s enemies. So an attack by a Tobacco Hornworm will trigger a new cry for help in a new chemical language, which only the hornworm-hungry Big-eyed Bug will hear.
(You know how anti-smoking advertisements like to list all the shit you’re smoking when you smoke cigarettes? Add to the list the chemical version of the Bat Signal. Doesn’t sound so bad now, huh?)
But the relationship is even more complex. The larval hawkmoth eats the plant, but the adult hawkmoth is its best pollinator. It’s a can’t-live-with-you, can’t-live-without-you situation. Tobacco’s solution to this dilemma is the ultimate in manipulation: it closes its legs. When it can’t stand being attacked by the hawkmoth’s larvae anymore, it simply ceases to flower at night, when the hawkmoth would normally visit it. Instead, it flowers in the morning, when it will attract hummingbirds. The hummingbird isn’t as good a pollinator, but the message is clear: Keep laying your eggs on me, buster, and I can take my loving elsewhere.