You probably already knew that fresh water is much more rare than salt water on earth. Since fresh water is relatively hard to come by there will be tremendous financial rewards to people who figure out how to make efficient use of salty water for human purposes. Yuka Yoneda, over at Inhabitat reports on a neat potential use of Mangrove Trees to purify water for agriculture purposes, specifically tomatoes (Bubble Shaped Skyscraper is a Fresh Water Factory). I hadn’t know that Mangroves could use brackish water to make fresh water for their own use and exude it in a way useful for other purposes. I suspect the capital required to make the spheres required for the project would make it uneconomical, but perhaps we’ll genetically modify other plants with the salt processing tools of the mangrove. Check out these amazing adaptions:
Full strength seawater has a salt concentration of about 34 parts per thousand, or 34 grams per litre. The cell sap concentration of the New Zealand mangrove is about 2 grams per litre.
This is much higher than land plants which have sap concentrations of 0.2 grams per litre, but still much lower than seawater.
This salt content in its sap is one of the secrets to its ability to survive in such a salty environment, by stopping water loss from the plant tissues.
The leaves of the mangrove also help the plant regulate its salt content by being able to secrete salt. Under a microscope hundreds of tiny pores can be seen on the upper surface of a mangrove leaf.
These are the openings of salt-secreting glands which get rid of extra salt by exuding a brine that is more concentrated than full strength seawater. Along with the salty residues of splash and spray, this is easily rinsed away by rain or the rising tide.
Another way of getting rid of salt is by shedding leaves. Many plants use this as a way of isolating and getting rid of unwanted chemicals in old leaves.
Mangroves lose about 60 percent of their leaves in a year. In summer, when the water loss through evaporation would be greatest, the mangrove increases its leaf drop by 10 times.