Salt-tolerant plants, astronaut pee, & the evolution of blood
I was looking into salt-tolerant plants for a piece of flash fiction I'm working on. It involves a conservationist trying to keep an invasive, man-eating species out of a local swamp. I wanted to know more about salt to really round out the worldbuilding. So I started digging into stuff like wars over salt, salt-tolerant plants, how animals handle salt...
- Scientists think that vertebrates evolved when the oceans were about a quarter as salty as they are now; the same salinity as vertebrate blood.
- Tamarisk trees secrete salt, but mangroves excrete it, sometimes through glands in their leaves, other times by concentrating it in old leaves and bark, which later drop. This lets mangroves survive in salty swamps.
- Historically, salt-cured meat was gray. Saltpeter is responsible for the red color of modern cured meats.
- The San Elizario Salt War of 1877 was fought over control of the of salt lakes at the base of the Guadalupe Mountains, which had previously been a communal resource and wound up privately owned by Americans.
- The scarcity of salt in the American South was a critical factor in the Confederacy's defeat during the American Civil War.
Scientists studying salt intake & urine in astronauts recently discovered that although increasing salt in the diet can lead to more urine output, this isn't actually linked to liquid intake; a high salt diet causes the body to break down fat and muscle, releasing water, similar to how camels survive in low-water environments. The process requires energy and often leads animals to eat more food (or lose weight, but this is a dangerous way to lose weight on purpose).
Freshwater fish have "physiological mechanisms" that concentrate salt in their bodies. Saltwater fish excrete unneeded salt thanks to their kidneys & chloride cells in their gills, which produce a particular enzyme. Fish that live in brackish environments can do both. Fish that can only handle one level of salinity are called "stenohaline" species, while more adaptable species are considered "euryhaline."
Salting foods like meat and vegetables tenderizes them because osmosis basically makes them excrete water. Sometimes, as with tomatoes and cucumbers in a salad, this is the opposite of what you want. It's really hard to taste the difference between different types of salt; the main differences have to do with the shape of the grains. Kosher salt doesn't have additives (like iodine or anti-caking chemicals) and is flakier, which makes it easier to pick up. Sea salt is mostly useful as a garnish, and colored salts tend to have more "natural" minerals, but all brands and types of salt have slightly different levels of "saltiness," which can make cooking with them tricky.
One of the oldest non-nomadic tribes in India, the Apatani, live in an isolated area with no access to saltwater or salt deposits. Instead, they eat tapyo, which is a bitter, filtered ash made from banana leaves, millet, and other local shrubs and bushes. It's a pain to make, but brings enough iodine into their diet to help avoid goiters and other health defects.
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