All living things need a certain amount of salt for survival. Excessive amounts of salt have adverse effects on animals and plants alike. In plants, too much salt can interfere with photosynthesis, the method by which plants make and store their food supply.
Photosynthesis uses the energy from the sun to convert carbon dioxide and water to glucose. The three chemical elements of glucose are carbon, hydrogen and oxygen. All are found in the nutrients, gases and water that the plants absorb.
Plants take water through their roots by a process called osmosis. Water passes through quite easily, but salts and other chemicals take longer. Salty water can actually pull the water out of the plant, causing dehydration.
Salt also has an adverse effect on a plant’s leaves. The stomata that allow the carbon dioxide in, as well as the excess oxygen out, can close up in the presence of too much salt.
A study at the Agricultural University of Plovdiv in Bulgaria on bean plants showed that excessive salt caused leaves to dry, turn yellow and then turn brown.The chloroplasts that hold the chlorophyll, the necessary chemical for photosynthesis, were damaged. The study also found that the root system was stunted.
Plants that live in a marine environment develop adaptations to the continual exposure to salt. Cordgrass is an example. Their leaves have special glands that excrete the excess salt.