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  • Thanks to Brilliant for supporting this episode of SciShow!

  • To learn more, go to Brilliant.org/SciShow.

  • [♪ INTRO]

  • More than half of the world's population depends on rice to survive.

  • But as the population grows, that demand is becoming harder to meet.

  • Right now, rice yield just isn't growing as fast as the global headcount,

  • and there's only so much room for more farms.

  • So unless we figure out an alternative, we might run into a serious problem.

  • Thankfully, this is something researchers are already working on,

  • and some of them have come up with a pretty clever potential solution.

  • To grow more rice, they're trying to entirely change the way the plant photosynthesizes.

  • Normally, rice uses what's called C3 photosynthesis.

  • This method is used by the overwhelming majority of photosynthetic life on Earth,

  • and it first evolved at least 2.7 billion years ago.

  • There's a lot to say about how this method works,

  • but there are only a few things you need to know to understand rice.

  • The first is that all the steps in C3 photosynthesis take place in the same area.

  • It all goes down in spongy tissues between the leaves' veins.

  • The second thing is that this process is kicked off by an enzyme called RuBisCO.

  • RuBisCO uses water, carbon dioxide, and energy to create an acid with 3 carbon molecules; hence “C3”.

  • Then, that acid undergoes a bunch of other reactions

  • and ultimately becomes a sugar that feeds the plant.

  • C3 photosynthesis is hugely important.

  • It's responsible for the millions of tons of rice we eat every year,

  • along with most of our other food energy.

  • And generally, it works pretty well.

  • But it's not perfect, especially when it gets hot.

  • Honestly, it's mostly RuBisCO's fault.

  • As the temperature increases, RuBisCO doesn't always process carbon dioxide

  • when it's trying to make that three-carbon acid.

  • Instead, it can sometimes process oxygen.

  • That wastes energy and water but doesn't actually create anything helpful for the plant.

  • And it's a problem especially relevant to rice.

  • As the climate warms, rice plants will likely become less efficient,

  • wasting all kinds of energy that could otherwise be turned into food.

  • It doesn't have to be this way, though, because C3 isn't the only kind of photosynthesis.

  • About 3% of terrestrial plant species, including some crops like corn, use a method called C4.

  • Kind of like C3, its get its name because it starts off by creating an acid with 4 carbons.

  • But the way it makes and processes that acid is very different.

  • For one, RuBisCO isn't involved in creating that molecule.

  • A different enzyme is responsible for that; one that can only process CO2.

  • Secondly, once that acid is created, it doesn't stay in the leaf's spongy tissue.

  • Instead, it's moved to a group of cells called a bundle sheath.

  • There, its broken back into CO2, RuBisCO takes over, and everything proceeds as normal.

  • This process may sound like it would decrease efficiency,

  • but it actually helps things flow more smoothly.

  • It sticks RuBisCO in its own little corner and only gives it carbon dioxide molecules.

  • That means there's no risk of the enzyme going rogue and processing a bunch of oxygen.

  • So the plant as a whole is much more efficient.

  • Now, C4 does have some downsides, like, it's not as efficient in cooler temperatures.

  • But in general, it seems like it would be great if we could engineer at least some rice plants to use this method.

  • That would just require, you know, dramatically changing the way they use photosynthesis.

  • Not a big deal or anything.

  • Maybe, though, it's not as impossible as you might think.

  • See, scientists have noticed that evolutionary pressure was so strong that

  • C4 and the structures that make it possible evolved multiple times. More than 60, in fact.

  • This suggests that going from C3 to C4 might not be that much of an ordeal.

  • Instead, researchers are hoping it may just require some relatively subtle changes to

  • the plant's genetic code.

  • So maybe, to convert a plant like rice to a drought-tolerant, ultra-efficient C4 machine,

  • you might just have to tweak a few parts of its DNA.

  • That's what scientists are investigating right now.

  • By studying plants like corn, they're trying to identify the exact mutations responsible for C4,

  • and then engineer those changes into plants like rice.

  • And they're making some good progress.

  • For example, some evidence has suggested that the anatomy needed for C4

  • might just be the result of genes for veins being expressed in the leaves as well as the roots.

  • So now it's just a matter of figuring out how to make that happen in actual rice plants.

  • This might sound like a whole lot of trouble just to mess with how a crop works,

  • but one team tackling this predicts that C4 rice would have 50% more efficient photosynthesis,

  • and would use half as much water as normal rice.

  • It should even require less nitrogen.

  • Some of the researchers involved in this work estimate that

  • this could boost global rice yield by 30% to 50%!

  • Which would be amazing.

  • After all, rice production needs to see a 50% increase by 2030 to keep up with population growth.

  • So C4 rice could be the answer we need.

  • Of course, even if C4 solves our rice problem, there will be plenty of other challenges to tackle in 2030.

  • And many of them will likely be studied using artificial intelligence.

  • AI can seem daunting, but there are great ways to learn about it,

  • like through Brilliant's course on Artificial Neural Networks.

  • The course starts with the basics and eventually gets you to more advanced techniques.

  • Along the way, there are all sorts of helpful diagrams,

  • and almost 30 quizzes where you can test your knowledge.

  • Brilliant also has a bunch of other courses about science, engineering, and math,

  • and they're working on new content all the time.

  • Much of it is also available offline through their app.

  • If you want to learn more, you can go to Brilliant.org/SciShow.

  • If you're one of the first 200 people to sign up at that URL,

  • you'll get 20% off an annual Premium subscription.

  • [♪ OUTRO]

Thanks to Brilliant for supporting this episode of SciShow!

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How We Could Prevent a Global Rice Shortage

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    林宜悉 posted on 2020/03/30
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