Salinity; found in two common forms - soil salinity and water salinity, plays a key part in the life of a plant. As their name may suggest, soil salinity is a salt concentration in soil and water salinity is a concentration of salt in water. The salinity concentration of a soil or solution can easily effect how a plant grows. Salinity concentrations differ according to the environment that they are found in, thus the salinity concentration of ocean or sea water is much higher than the salinity concentration of a garden bed or water from a tap.
The average salinity concentration of sea water is 3.5% (http://seagrant.gso.uri.edu/factsheets/salt.html,2010). This concentration is made up of several salt types, the most common being sodium chloride (NaCl), magnesium chloride (MgCl2) and calcium chloride (CaCl2)(http://www.supergreenme.com/go-green-environment-eco:Salinity, 2010). Due to the high concentration level of sea water only some plants are able to live in this condition. Mangroves are an example of one type of plant that has adapted to live in these conditions with their salt excreting glands. Although most plants do not have this adaption and thus salinity concentrations in garden soil or potting mix is much lower, however, over time salt can accumulate and result in an increase in soil salinity.
The concentration of salt can have drastic effects on a plant’s growth and life span. Osmosis; the diffusion of water through a semi permeable membrane from an area of high concentration of water, to an area of low concentration of water (dictionary.com, 2010), can be used to explain the effect of salinity on plants. If the water or soil salinity outside of the plant is more concentrated than the salinity concentration inside the plant’s cells, water will osmose out of the plants cell, and into the soil (http://ezinearticles.com/?Understanding-Salinity-and-Osmosis-for-a-Sustainable-Garden&id=795763, 2010). In turn, the plant will lose water, causing the leaves to shrivel. This means that the area of leaf available needed for photosynthesis to occur will decrease and the plant will most likely die.
The salt tolerance level of a plant is defined as the stage in which the studied plant begins to show little or no growth increase at a certain concentration (http://www.sebiology.org/publications/Bulletin/July05/salinity.html, 2005). Studies show that the theoretical tolerance concentration level of sodium...