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  • [Intro]

  • Being warm-blooded is really convenient.

  • For one thing, you can go outside when it’s snowing or hot without having to worry too

  • much about your body processes shutting down.

  • But not all organisms regulate their body temperature, because it’s a big drain on

  • energy resources. It’s mostly just birds, mammalsand some plants.

  • A few hundred species of plants produce their own heat in a process called thermogenesis,

  • and some of them use that heat to regulate their body temperature.

  • It’s based on the same idea as warm-bloodedness in animals: energy can be released as heat.

  • Plenty of your normal, everyday metabolic processes, like digestion, release heat as

  • a byproduct.

  • But if that’s not enough, you can also shiver, causing the chemical processes involved in

  • muscle contractions to release more heat.

  • When an animal can’t shiver -- like a newborn human baby, or a hibernating bear -- it can

  • burn brown fat instead, a special kind of fat that’s full of glucose and produces

  • lots of heat when it’s broken down.

  • But plants can’t shiver, and they don’t have brown fat.

  • So plants produce heat using another mechanism, a type of cellular respiration known as thermogenic

  • respiration that takes place in their mitochondria.

  • Mitochondria are usually described as the powerhouses of the cell, and for good reason:

  • their job is to store energy in the form of the molecule ATP.

  • But in thermogenic respiration, the mitochondria skip the ATP and just release the energy as

  • heat.

  • At the most basic level, thermogenesis just keeps these plants warmer than their surroundings.

  • But a handful of species, like the eastern skunk cabbage and the sacred lotus, take it

  • one step further, with feedback mechanisms that they use to keep their body temperatures

  • within a certain range -- or thermoregulate.

  • In thermoregulatory plants, decreasing internal temperatures trigger more cyanide-resistant

  • respiration, keeping them warm. And if their temperatures get too high, they just produce

  • less heat and start to cool off.

  • Now thermogenesis might seem like a huge waste of energy -- and it is. But for these plants,

  • the advantages make the energy loss worth it.

  • In some cases, it helps them avoid frost or keep snow away.

  • The skunk cabbage, for example, can melt through snow, giving it early access to pollinating

  • insects while other plants are still buried.

  • But many thermogenic plants are tropical, so they wouldn’t have much reason to develop

  • resistance to frost. And plenty of plants bloom just fine when it’s cold out.

  • Other plants are trying to attract pollinators, either by providing the perfect temperature

  • for mating insects, or just by making themselves smellier.

  • Like a dumpster on a hot day, a warmer plant will smell a lot worse.

  • For instance, when a dead horse arum is blooming, it releases more than a hundred volatile compounds

  • in its attempt to lure hungry bugs to the smell of rotting flesh.

  • It only blooms for a couple of days every few years, so it needs to attract as many

  • pollinators as possible.

  • But it also needs to trap them there for a while.

  • In the dead horse arum, the female florets mature on the first day, but the male florets

  • mature on the second day. So the pollinators are most effective if they stick around long

  • enough for both phases.

  • When a fly crawls down into the base of the flower, a series of spines keep them from

  • getting out again. Hopefully, the fly’s picked up pollen from an earlier-blooming

  • flower, so the female florets get pollinated.

  • The next day, the male florets release their pollen, which attaches to the fly. Then, the

  • spines wither, so the fly can go free, and it falls for the same trick again, landing

  • on what it thought was a lump of dead flesh but turns out to be another flower in disguise.

  • Good news for the bugs though: there might be benefits for them too.

  • One study looked at the species of beetles that pollinate thermoregulating philodendrons.

  • Normally, these beetles have to produce lots of heat themselves so that they can stay active

  • at night.

  • But the researchers found that when the insects were trapped in the flowers overnight, they

  • only needed to use about half as much energy.

  • For an insect, landing a thermogenic plant is like curling up next to a nice, warm radiator.

  • Justone that happens to smell like a dead horse.

  • Thanks for watching this SciShow Dose and thanks especially to our patrons on Patreon.

  • This episode’s President of Space is SR Foxley. If you’d like to be President of

  • Space or get other cool rewards for supporting SciShow content, head on over to patreon.com/scishow.

  • And of course, as always, if you want to keep getting smarter with us you can go to youtube.com/scishow

  • and subscribe.

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B2 中高級

能讓自己保持溫暖的植物 (Plants That Keep Themselves Warm)

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    Jack 發佈於 2021 年 01 月 14 日
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