Wednesday, June 6, 2012

Glasswort by any other name: Salicornia

Yesterday we saw the most obvious way for a plant to deal with excess salt -- by taking it up and then immediately getting rid of it. That strategy works, as the dunegrasses' success can attest, but there's more than one way to peel an orange. Today, let's have a look at Salicornia, a genus with a lot of names (glasswort, pickleweed, sea pickle, marsh samphire, pousse-pierre...) and one interesting way of dealing with salt.
Salicornia virginica in flower.
The blossoms are those tiny
stringlike structures at the ends
of the branches.

Salicornia plants are odd-looking little things, though you might have to get close to see very much; most species don't get much larger than a foot tall. With their thick, succulent stems and tiny, scale-like leaves pulled in close, they look mostly leafless, and indeed the stems do most of their photosynthesis. Some species are edible, sold as a delicacy under the names "sea beans" or "samphire greens"; it's also been used in the glass industry, as a source of soda ash. These two uses, as a salty food and as a source of sodium carbonate, betray one important fact: mature Salicornia plants are chock full of salt. Yes, it's the same salt you're thinking -- sea salt, table salt, salt that sucks the water right out of living things.

How do they manage it without dying of dehydration? Glassworts, it turns out, have a special modification to their cells' vacuoles. Virtually every plant cell has a vacuole; it's essentially just a large membrane-bound bubble in the middle of the cell, which the cell uses to store water, control its size, and dump substances it doesn't want. For Salicornia, those substances include salt. It can keep salt locked up in the vacuole even when the concentrations inside are many times that of the rest of the cell, high enough that most plants couldn't keep the stuff contained and would die of dehydration. For these tough little oddballs, it isn't a problem; they just go on doing their thing with bubbles of saline death locked down right in the middle of every cell.

Hence their names: pickleweed for the salty flavor, sea pickle for the tolerance to ocean salinity, glasswort for being so rich in salt that the glass industry once used them as sodium collectors.

Image source: Folini, Franco. American Glasswort (Salicornia virginica) (6122382261). Retrieved 6 Oct 2014, from Wikimedia Commons: <>

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