JUNE 2024 — BIOLOGY STD 12 Science — Question

→ Due to our present day life styles, environmental pollution is a major cause of concern.
→ The use of chemical fertilizers to meet the ever-increasing demand of agricultural produce has contributed significantly to this pollution.
→ There are problems associated with the overuse of chemical fertilizers and there is a large pressure to switch to organic farming - the use of biofertilizers.
→ Biofertilizers are organisms that enrich the nutrient quality of the soil,
→ The main sources of biofertilizers are bacteria, fungi and cyanobacteria.
→ The nodules on the roots of leguminous plants are formed by the symbiotic association of Rhizobium.
→ These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as nutrient.
→ Other bacteria can fix atmospheric nitrogen while free-living in the soil Azospirillum and Azotobacter, enriching the nitrogen content of the soil.
→ Fungi are also known to form symbiotic associations with plants(mycorrhiza).
→ Many members of the genus Glomus form mycorrhiza.
→ The fungal symbiont in these associations absorbs phosphorus from soil and passes it to the plant.
→ In paddy fields, cyanobacteria serve as an important biofertilizer.
→ Currently, in our country, a number of biofertilizers are available commercially in the market and farmers use these regularly in their fields to replenish soil nutrients and to reduce dependence on chemical fertilizers.
→ In agriculture, there is a method of controlling pests that relies on natural predation rather than introduced chemicals.
→ The use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides.
→ A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma. Trichoderma species are free-living fungi.
→ Trichoderma is a biocontrol agent of several plant pathogens.