Page 16 - Curriculum Visions Dynamic Book

Salt and living things
In living things all cells are surrounded by semipermeable membranes.
The walls of the cells are able to filter out some molecules and let others pass through. In this way they can eject waste materials and absorb nutrients while keeping all other materials out.
The way that osmosis works can
easily be demonstrated with a carrot.
If the carrot is placed in a saline
solution, water flows out of the carrot cells to dilute the saline solution, and the carrot shrivels. If the carrot is now placed in pure water, the water flows into the carrot and it swells.
In nature, the concentration of saline solution is critical. In animals, if it exceeds 0.9% then there is a real chance that
the effect of osmosis will be so powerful that the cells will be ruptured. Plants, by contrast, have much stronger cell walls and can put up with a high saline solution.
 Mangroves thrive in coastal conditions, as they are able to withstand salt.
 If you put a carrot in a strong brine solution, natural osmosis will work on the cells of the carrot tissue and the carrot will shrivel up. This gives a very dramatic impression of the power of osmosis. In the picture above, the carrot has been placed in distilled water, while the picture on the right shows a carrot that has been placed in strong brine.
Plants that thrive in salt water
Many plants thrive in salt water. Indeed, plants are common in the sea. Algae, the microscopic green plants that float on the surface of the sea, are at the bottom of the sea food chain. Other large plants, such as seaweeds, are common sea water plants.
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