Originally published at: https://boingboing.net/2018/05/08/tomato-plants-can-detect-an-im.html
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This reminds me of other research that indicates plants use airborne signals (incl. the methyl jasmonate used in this study) to communicate they’re being munched, stimulating other plants to upregulate chemical defenses. Or in other words, the crisper the lettuce, the more it screams.
I wonder if it’s a similar receptor mechanism.
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I have a follow-up question. Why didn’t tomato plants just evolve to taste bad to snails and caterpillars all the time? Rose bushes don’t have retractable thorns that only pop out when grazing animals or love-smitten humans are nearby.
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Because evolution isn’t goal oriented!!! It’s all about tradeoffs, and it’s probably more costly to maintain a constituitive defensive metabolite cocktail than it is to upregulate when the threat presents itself. Literally just graded a hundred tests where this was the answer to a question.
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Roses are lazy.
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I suspect it is either mildly toxic to the plant itself or requires a lot of energy that could otherwise be used to grow taller than the surrounding plants.
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OK, I’m converted. Dear scientists, please go ahead and develop genetically modified vegetables of all kinds which have the genes that enable this, so I can stop my ceaseless stalemated war against slugs and snails determined to ruin my veg crops. 
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Isn’t this a bit like saying that sponges detect water and swell up in its presence?
It seems to me that the strategy of fruit bearing plants is to have the fruit be eaten to further distribute seeds than a local drop would provide. If it tasted bad all the time, that would defeat the reason you spend on that energy on a fruit in the first place.
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Does it taste bad to the animals that the fruit evolved to attract, though?
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Let’s put it this way, if a happy little goat came across some tomato fruit and some of it smelled kinda off and the other bushes didn’t, who do you suspect would get their seeds spread?
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Violets are energetic.
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If tomatoes would like me to start distributing their seeds, they need to make some effort to start tasting like chocolate.
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There are certainly cases like that in nature. Hot peppers for example. Most mammals (other than humans) dislike spice and avoid eating peppers. Birds on the other hand cannot taste spice and eat them just fine. While it is always a bit of conjecture as to the “why” in evolution, an obvious hypothesis is that having birds distribute pepper seeds turned out to be more adaptive than mammals (which not only have smaller ranges but have more efficient digestive systems that may destroy the seeds).
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Tomatoes are a fruit.
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Very few if any fruit-bearing plants upregulate chemical defenses in the fruits themselves after ripening; after all, they are intended to be taken for distribution. Any remnant metabolites in the fruit itself is to deter frugivory from any but the intended distributor, (e.g., bitter atropines in nightshade berries to deter mammals, but not birds.)
Tomatoes are horticultural monstrosities, but if we look at a closely related species, (Bittersweet nightshade, for example, where the fruits retain those defenses, see above,) it’s probable they have a very similar adaptation to deter herbivory, since their chemical cocktails are just as costly to produce.
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Hmm, now the squirrel who picked the very first tomato last year, took one bite, and left the rest of the fruit on the ground to rot seems less crazy…
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Because they’re GMO’s. Tomatoes are part of a bad-tasting poisonous family (the nightshades), but we’ve bred them to have such huge berries that taste better (not poisonous yucky) that they’re no longer as tough as they had once evolved to be.
Edit: The greenery is still poisonous yucky, just not the berries. Central American cuisine boils deadly nightshade greens to eat like spinach. The boiling kills the poison and the yucky taste.
"The plant belongs to the nightshade family, Solanaceae.[1] The species originated in western South America.[2][3] The Nahuatl (Aztec language) word tomatl gave rise to the Spanish word “tomate”, from which the English word tomato derived.[3][4] Its use as a cultivated food may have originated with the indigenous peoples of México."
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Oh, YEAH? I can top that. A couple of summers ago, a squirrel with a tree fort in my front yard bombardiered a half-eaten tomato onto my shoulder. She had stolen the tomato from the yard across the street, then wasted half of it on a target of opportunity.
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