Abstracts |
Soil salinity is world wide problem because it negatively affect plant productivity and yield of plants particularly in arid and semi-arid regions of the world. Excessive salts decline soil water availability for plants, inhibit plants metabolism and nutrients uptake and is also responsible for osmotic imbalance. All of these changes contribute to stunted growth and less productivity of plants. Exploitation of soil microorganisms for utilizing salt affected soils is of considerable interest to plant and soil scientists. Arbuscular mycorrhizal fungi (AMF) are ubiquitous soil microorganisms inhabiting the rhizosphere and establish a symbiotic relationship with the roots of many plants. Arbuscular mycorrhizal fungi are from integral components of all natural ecosystems and are known to occur in saline soils. Symbiotic association of a plant with AMF results in higher ability for taking up the immobile nutrients in nutrient-poor soils as well as improvement of tolerance to salinity. The possible mechanisms for alleviation of salinity stress by AMF include: (1) improvement of plant nutrient uptake, particularly P, (2) elevation of K:Na ratio, (3) providing higher accumulation of osmosolutes, and (4) maintaining higher antioxidant enzymatic activities. In addition, some aquaporin genes are up-regulated in mycorrhizal plants, causing significant increase in water absorption capacity of salt-affected plants. In contrast, expression of proline biosynthetic enzymes and LEA genes as stress indicators are maintained in mycorrhizal salt stressed plants suggesting that mycorrhizal plants are less susceptible to salinity because of salinity-avoidance mechanisms. |