ROLE OF AM FUNGI IN BIOREMEDIATION AND AGRICULTURE

Role of AM Fungi in Bioremediation of Heavy metals in Soil

• Heavy metals may accumulate in food crops, fruits, vegetables, and soils, causing various health hazards.
• AM Fungi can potentially promote plant growth in contaminated soils, a capacity commonly referred to as bioremediation.
• AM Fungi are widely believed to support plant establishment in soils contaminated with heavy metals, because of their potential to strengthen defense system of the plants to promote growth and development.
• Plants grown on soils enriched with Heavy metals exhibit considerable suppression in shoot and root growth, leaf chlorosis, and even death. Heavy metals can be immobilized in the fungal hyphae of internal and external origin that have the ability to fix heavy metals in the cell wall and store them in the vacuole or may chelate with some other substances in the cytoplasm and hence reduce metal toxicity in the plants.
• AM Fungi reportedly bind with Heavy metals in the cell wall of mantle hyphae and cortical cells, thereby restricting their uptake and resulting in improved growth, yield, and nutrient status.
• Various processes that occur through the AM Fungi are Immobilization or restriction of metal compounds, precipitation of polyphosphate granules in the soil, adsorption to fungal cell wall chitin, and heavy metal chelation inside the fungus.

Role of Arbuscular Mycorrhizae (AM) Fungi in Agriculture

• Arbuscular Mycorrhizal associations are particularly beneficial in areas where the soil does not contain sufficient Nitrogen and Phosphorus, as well as in areas where water is not easily accessible.
• AM Fungal colonization include increased absorption and uptake of nitrogen, potassium, magnesium, copper, zinc, boron, sulphur, molybdenum and other elements that are transported back to the plant.
• The Arbuscular mycorrhiza fungi are the well known for their ability to improve plant growth in low phosphate soils by exploiting large areas of soil and actively transporting the phosphate back to the plants.
• Mycorrhiza mixed nitrogenous compounds such as nitrate; ammonia etc. is available to the plants. Thus, it helps in plant growth, especially in acid soil.
• Arbuscular mycorrhiza increases the nodulation and nitrogen fixation in legumes by supplying phosphate.
• Mycorrhiza helps in mobilization of Phosphorous.
• AM fungi helps in retaining moisture around root zone of plants.
• The mycorrhizal association helps in the formation of dichotomous branching and profuse root growth, thus enhances plant growth.
• AM fungi can possibly lower down the use of chemical fertilizers up to 50 % for best agricultural production, but this estimate depends on the type of plant species and the prevalent stressful regimes.
• Mycorrhizal growth causes the synthesis of Phytoalexins - Orchinol and Hirsinol. Both the compounds act as a barrier to protect infection by other pathogens.
• The application of mycorrhizal fungi in forest bed enhances the formation of mycorrhizal association that prevents the entry of fungal root pathogens.
• Arbuscular mycorrhiza is well known to compete with other members of the soil biota for soil nutrients thereby increasing the competitive ability of their host plants.
• AM Fungi and their interaction with the host plant are helpful in supporting plants against severe environmental conditions.
• Arbuscular mycorrhiza is also reported to increase the tolerance of plants to diseases and pests by compensating for root damage and were observed to possess direct negative effects on the pathogens.