Tag: zoology

Biofertilizers are the suspension of microorganism which is formed by ploughing in legumes. They enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi, and cyanobacteria (blue-green algae). Biofertilizers will help solve such problems as increased salinity of the soil and chemical run-offs from the agricultural fields.

Nitrogen is the important nutrient for plant growth. Plant obtains nitrogen from the atmosphere with the help of symbiotic and free nitrogen-fixing microorganisms. Azotobacter  is aerobic free living nitrogen fixing organism and fixes atmospheric nitrogen non-symbiotically. Therefore, all plants, trees, vegetables get benefited. Whereas VAM, Anabaena and Rhizobium are the symbiotic organisms. 

Blue-green alga like Nostoc, Anabaena fix atmospheric nitrogen and hence enhance soil fertility. Hence, these organisms are used as biofertilizers. Blue-green alga has special thick-walled cells, called as heterocysts, which carry on the process of fixation of atmospheric nitrogen.

Green manure acts mainly as soil acidifying matter to decrease the alkalinity/pH of alkali soils by generating humic acid and acetic acid. The root systems of some varieties of green manure grow deep in the soil and bring up nutrient resources unavailable to shallower-rooted crops. Erosion control is often also taken into account when selecting which green manure cover crop to plant.

Water bloom is a dense aquatic population of microscopic photosynthetic organisms produced by an abundance of nutrient salts in surface water, coupled with adequate sunlight for photosynthesis. The microorganisms or the toxic substances that they release may discolour the water, deplete its oxygen content, poison aquatic animals and waterfowl, and irritate the skin and respiratory tract of humans. It majorly caused because of Cyanobacteria and dinoflagellates. 

Azolla pinnata is an aquatic fern, which contains a nitrogen-fixing cyanobacteria. It contains Anabaena azollae in its leaf cavities. It is an excellent biofertilizer for paddy fields because they can fix nitrogen in moist condition also.

The pink color, typical of healthy and effective nodules, is due to the presence of a protein called leghemoglobin. This special protein contains Iron (Fe) and molybdenum (Mo) and is responsible for binding oxygen. This provides sufficient oxygen for the metabolic functions of the bacteroids but prevents the accumulation of free oxygen that would destroy the activity of nitrogenase.

Bacillus thuringiensis (Bt) is commonly used as a biopesticide. It is sporulating, a gram-positive facultative-aerobic soil bacterium. It synthesizes the proteins known as delta endotoxins or cry proteins which infect the insects by paralyzing the digestive tract and makes it porous.