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We’d pictured the plant-fruit relationship as one-way, but new research reports that sometimes the fruit can talk back! And while cow burps are a widely cited contributor to climate change, it turns out that wild pigs might also be contributing with their eating habits.

Hosted by: Hank Green

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Sources:
https://www.frontiersin.org/articles/10.3389/fsufs.2021.657401/abstract
http://www.ncagr.gov/CYBER/kidswrld/plant/nutrient.htm
https://www.cell.com/trends/plant-science/fulltext/S1360-1385(21)00064-9
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https://pubmed.ncbi.nlm.nih.gov/8567486/
https://www.smithsonianmag.com/smart-news/feral-pigs-are-invasive-voracious-and-resilient-theyre-also-spreading-180973824/
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Images:
https://www.istockphoto.com/photo/laughing-orange-and-lemon-with-leaf-isolated-on-white-background-gm924169600-253643602
https://www.istockphoto.com/photo/ripening-raspberries-on-the-vine-gm626122442-110447663
https://www.istockphoto.com/photo/tomatoes-gm98026003-12342829
https://www.frontiersin.org/articles/10.3389/fsufs.2021.657401/full
https://www.istockphoto.com/photo/caterpillar-on-red-apple-gm140984437-17978742
https://www.istockphoto.com/photo/wild-boars-feeding-on-green-grain-field-in-summer-gm1216933946-355023904
https://www.istockphoto.com/photo/wild-boar-sus-scrofa-digging-on-a-meadow-throwing-mud-around-with-its-nose-gm1148419256-310137920
https://www.istockphoto.com/photo/earth-texture-macro-photography-pattern-background-gm1277752567-376879187
https://www.istockphoto.com/photo/group-of-wild-boars-sus-scrofa-running-in-spring-nature-gm1159631033-317157440
https://www.istockphoto.com/photo/massive-wild-boar-sus-scrofa-showing-up-on-the-green-forest-clearing-gm1238287956-362491572
https://www.istockphoto.com/photo/wild-boar-gm466390207-33669694
[♪ INTRO].

Outside of children’s cartoons, fruits aren’t very chatty. Or so we thought.

We know that different parts of a plant are capable of communicating with one another. But we’d pictured the plant-fruit relationship as pretty one-way. Plant invests a lot of resources in fruit, fruit… grows.

Now, however, researchers out of Brazil report that tomatoes can send out a distress signal to their parent plant when they’re under attack from hungry caterpillars. This tells us we still have a lot to learn about how plants communicate. And if we can learn to talk to fruit, they may be able to help us protect them from climate change.

Ok. So, we know that nutrients travel from the plant to the fruit it produces. That makes sense, because the plant is pouring resources into reproduction.

Up until now, there’s been little research looking at whether anything at all is traveling back from the fruit to the plant. But fruits are made up of living tissue, same as the rest of the plant. So it stands to reason that the fruit may have a way of communicating with its parent plant.

Researchers at the Federal University of Pelotas and the Brazilian Agricultural Research Corporation hypothesized that fruits could be communicating through electrical signals. Prior research has found other parts of plants can do this as a way of sending long-range signals, particularly when they’re under stress. So the team measured the electrical activity coming from tomatoes before, during, and after a 24-hour snack attack by caterpillars.

How did they do it? Well, they inserted a pair of electrodes into the stems of tomatoes that were attached to their parent plants, and they placed the entire set up inside an enclosure that blocks electromagnetic fields. That way, they would detect only the electrical signals coming from the fruit.

The researchers used machine learning to determine whether there was a pattern in the electrical signals they were measuring from the fruits. Basically, it’s good to have a computer help humans out when interpreting something complex like electrical signals. And they found a clear difference between the electrical signals coming from the tomato fruit before and after the caterpillar attack.

They also looked at whether there was any biological response from the plant. To do that, they measured the production of hydrogen peroxide, a chemical that’s often produced by tomatoes when they’re getting nibbled on by pests. The tomato plants ramped up their internal production of hydrogen peroxide in defense against potential caterpillar-induced obliteration.

Now, this research is still preliminary, but it opens up a whole world of talkative fruit to study. If we could understand when fruits were saying, “help me, I’m being eaten by a bug,” that could help farmers detect infestations earlier. And that would help them manage pest insect populations more efficiently, and less aggressively.

And this could come in handy, especially as Earth’s constantly warming climate encourages more aggressive pest infestations. Speaking of agriculture and climate change, new research from a group of international researchers out of Australia highlights a potentially overlooked problem relating to our animals. Domestic cattle are widely cited as significant contributors to climate change, thanks in part to their methane-laden burps.

But this newly published study looked at pigs. And not the ones we raise deliberately, but feral pigs. And the results are not so hot.

The researchers found that wild pigs worldwide are releasing almost 5 million tonnes of carbon dioxide per year into the atmosphere, an amount equivalent to the emissions from around 1 million cars. But unlike cows, where the problem is what comes out of their mouths, these pigs… eat like pigs. You see, feral pigs are incredibly destructive critters.

They’re basically little four-legged tractors, trundling along, churning up the soil in search of some delicious below-ground snacks. And most of Earth’s terrestrial carbon is stored in soils, mainly as dead and decaying plant matter. Most of this stays trapped in the top meter of soil.

A small amount might escape as carbon dioxide gas as soil microbes break down the plant matter, but much of the carbon remains behind. That is, unless it’s dug up by something like a tractor or a pig. Once all this carbon gets churned up, it can decompose and get released directly into the air instead.

So as these pigs churn up the soil with their snouts, they’re releasing a lot of that stored up CO2 into the atmosphere. Now that’s partly because there are a lot of feral pigs. And we’re not even really sure how many.

The researchers had to use computer models to estimate the current population of wild pigs across five continents. They generated simulated maps of the pigs’ current range and density. Then, they modeled the damage the pigs are doing to the soil, and simulated the global emissions that damage would cause.

In other words, it’s a rough number, but it reminds climate researchers to pay attention. Because invasive feral pig populations are on the rise. And climate change means milder winters, which make it even easier for the pigs to find food and expand their ranges even further north.

So these pigs are not only hurting the planet, they are helping themselves in the process. The good news is, this research provides a way to highlight ecosystems most vulnerable to porcine plundering, and it shows where interventions are most needed. Which might help eradication efforts in the future.

Thanks for watching this episode of SciShow News, and thanks to all of our patrons for making it possible. Y’all are the coolest community ever, and SciShow is very lucky to have you. If you want to get involved, you can get started at patreon.com/scishow. [♪ OUTRO].