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The Water Chestnut

Botanical illustration of Eleocharis dulcis, the Water Chestnut

Botanical illustration of Eleocharis dulcis, the Water Chestnut

The water chestnut is one of those foods I’ve eaten my whole life without knowing anything more about it than flavor and appearance (and that only because it so often shows up in frozen vegetable mixes).

The scientific name for the Water Chestnut isĀ Eleocharis dulcis, and it’s often classified as a sedge.* It’s also a quite awesome plant. Consider:

  • The visible parts of a water chestnut plant are leafless stems that perform photosynthesis. (The water chestnut has almost completely abandoned leaves!)
  • The edible part of the plant is a botanical structure called a corm** which is a modified underground stem used by a plant to store energy (water chestnut plants are very much about stems). Not to be confused with bulbs like those of onions and garlic, which can look similar, but are instead made up mostly of leaves
  • The reason water chestnuts remain so crunchy after cooking is that their cell walls are reinforced by special phenolic compounds, the same class of molecules as capsaicin, the molecule that makes chilli peppers spicy.

The genus Eleocharis also contains species like Eleocharis vivapara which switch between C3 and C4 forms of photosynthesis depending on whether they’re grown on dry land or in swamps. The relative advantages and costs of these two different forms of photosynthesis are worth a post on their own, but I’d always assumed it was an either/or choice and didn’t realize ANY plant species could pick to use whichever system was best suited to the local environment.[citation]

Domestication:

Canned Water Chestnuts photo: kattebelletje, flickr (click photo to see in original context)

Canned Water Chestnuts photo: kattebelletje, flickr (click photo to see in original context)

The ancestors of water chestnuts were weeds in early rice paddies. It’s easy to imagine some rice farmer living six thousand years ago sampled the weird bulbous corms attached to the roots of the weeds she had just finished pulling from herfield and found them delicious (or at least not poisonous). Over time this rice farmer encouraged this edible weed at the expense of other, useless weeds, even saving corms or seeds from the occasion bigger, or better tasting, or in some other way more desirable plants and planting them in a separate field the next year. Eventually the practice spread to other farmers, and the domesticated water chestnut was selected into existence.

And that, as nearly as I can piece it together, is the story of the water chestnut, an awesome domesticated weed that does amazing things with stems.

More detail on the agriculture of water chestnuts.

*Sedges can look a lot like grasses, but botanically aren’t. They do belong to the same group of species, monocots, as the grasses do, but it’s a group that also includes everything from bananas to pineapples.

**Not just cool because it looks sounds like corn

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2 Comments

  1. Anastasia says:

    Cool! I didn’t know that plants existed that could switch between C3 and C4 photosynthesis. Do you know if it’s fixed for the life of the plant, or can it go back and forth?

    Polyphenols have anti-nutrient properties – they reduce the bioavailability of some minerals. I wonder if the phenols in the cell walls of water chestnuts do this as well. If so, that could be a problem for vegetarians who rely on stir fries with water chestnuts for a lot of their meals. Interesting.

    1. James says:

      From my reading of this section of the review article (makes me wish I’d taken more botany in school), it sounds like individual photosynthetic stems are fixed as either C4 or C3 photosynthesis, but when the plants are transplanted from one environment to another, they grow new leavesphotosynthetic stems that use the appropriate form of photosynthesis for their new environment.

      I’m surprised there hasn’t been more study of E. vivipara, it sounds like a fascinating plant, and can you imagine having crops that could respond to water or heat stress by growing new C4 photosynthetic leaves.

      I sure hope someone has checked if water chestnuts are anti-nutritive, but if one is going to eat phenolic compounds, having them crosslinked with undigestible cell walls is probably the safest way to do so.

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