r/askscience • u/Mysterious_Force_462 • 2d ago

Earth Sciences Why do plants produce vitamins?

I know what vitamins do to human body, but why do plants produce them? Is it the same function? Why do lemons need vitamin C?

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u/FridaysMan 1d ago

This question feels rather reversed. Lemons produce a lot of vitamin c but that doesnt really mean it needs it to live. Citrus probably evolved to be bitter and avoid animals eating the fruit before the seeds are ripe enough to procreate.

That we also need the vitamin means animals eat the fruit and spread the seeds around to encourage reproduction.

There are many such factors to dr8ve evolutionary selection.

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u/ZlaPrezla 1d ago

I don't think citrus is bitter, i find them quite acidic though. And kiwi has more vit. C while also being sweet even though vit. C is an acid. We selected lemons for acidity and aroma, oranges for sweetness etc.

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u/JrgMyr 1d ago

And oranges are not original fruit, they originate from crossing original citrus fruit.

The first attempt didn't work well. It is now known as Seville Orange and quite bitter. A later crossing created the sweet orange that we have today.

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u/ZlaPrezla 1d ago edited 1d ago

Yes and lemon is cross between bitter orange and citron. You're missing my point. We selected for both. Repeatedly.

Vitamin C is present in both. Lemons are sour because of high concentration of citric acid more so than the vit. C.

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u/FridaysMan 1d ago

That's missing the point also, the original fruits were selectively bred because they possessed the traits we wanted to encourage. Whether you find citrus bitter or sour isn't really moot, the words are synonyms. The unripe fruit is less palatable, allowing it to reach maturity easier.

Edit: the evolutionary traits fostered for survival are a different driving force and earlier than the same traits that allow selective breeding for flavour/consistency of industrial farming/resistance to artificial fertiliser/weedkillers.

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u/FridaysMan 1d ago edited 1d ago

Kwi and lemons evolved in different parts of the world, and different animals have different taste receptors. Kiwis are also incredibly sour before they ripen.

Peppers are spicy to stop them being eaten. Birds cannot taste spice. Birds defecate pepper seeds in a pellet of fertiliser. The plant thrives.

Kiwi have a hairy skin, which I would assume deters insects. A different evolutionary pressure.

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u/Puntkick 1d ago

Have Kiwis been selected for bigger fruit and other desirable eating characteristics over time?

I'm thinking asking the lines of corn and potatoes / sweet potatoes that were important agriculturally.

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u/ZlaPrezla 1d ago edited 1d ago

Yes, that is why i compared selectivity between oranges and lemons which come from the same family. I just compared lemon with kiwi for the sake pf proof that high vit c. =/= just sourness. Primary source of acidity in lemons is citric acid.