How plants deal with osmotic stress

Much work is being carried out into plant salt tolerance. It is thought that a better understanding of how plants are able to deal with stresses that growing in saline environments will help breeders develop plants that will be able to generate higher yields in lands that have high salinity. As ~20% of all arable lands is known to have high levels of salt, the development of salt tolerant crops may greatly help in eliminating in world hunger.

Dealing with Increased Osmotic Potential

There are many mechanisms that plants have developed for dealing with increased salt levels and these include compartmentalisation of salt into vacuoles and the limitation of long distance transport of salt from the root to a plants aerial parts.

One of the main things that a plant needs to grow is water, in areas of high salinity the osmotic potential is dramatically altered, leading to osmotic stress and possible injury from salt stress. The next section takes a look into the mechanisms that a plant can employ to overcome osmotic stress related problems.

Osmotic Stress

One of the ways in which plants are able to cope with high levels of osmotic potential is to store sodium in vacuoles; this process results in a lowering of osmotic potential and a lowering of stress.

However, when plants are growing in arable land that has a high salinity then the accumulation of sodium may become a limiting factor, this is especially the case in glycophyte crop plants that do not have the mechanisms to store large quantities of salts in their vacuoles. In these circumstances there will be an increase in the osmotic potential resulting in a plant not being to take on-board the required amount of water, leading to a decrease in growth and a lack of vigour.

Altering osmotic potential through osmolytes

In addition to compartmentalisation, a way in which a plant may overcome osmotic stress is to increase the production and accumulation of osmolytes such as proline, polyols and glyceine betaine; these osmolytes can help to reduce the damage done to plant cells through osmotic related stress. The production of osmolytes leads to a plant becoming more tolerant of salt.

Osmolytes work to reduce osmotic stress and increase a plants ability to cope with salt by reducing osmotic potential, reducing reactive oxygen species, and perhaps most importantly, protecting proteins from misfolding.