Biofertilizer Questions in English

(D) Organic farming is a sustainable agricultural system that avoids the use of synthetic chemical fertilisers and pesticides.
$I.$ The use of biofertilisers (like cyanobacteria,mycorrhiza) and biopesticides (like $Bacillus$ $thuringiensis$) is a core component of organic farming to maintain soil fertility and control pests.
$II.$ Crop rotation is a traditional practice used in organic farming to improve soil health,manage nutrients,and break pest/disease cycles.
$III.$ The use of locally developed pest-resistant varieties is encouraged in organic farming to reduce reliance on chemical pesticides and adapt to local environmental conditions.
Since all three statements ($I, II,$ and $III$) are integral practices of organic farming,the correct option is $D$.

(B) Biofertilisers are organisms that enrich the nutrient quality of soil. They include bacteria,fungi,and cyanobacteria that fix atmospheric nitrogen or solubilise phosphorus,thereby enhancing soil fertility naturally.

(A) Biofertilisers are organisms that enrich the nutrient quality of the soil.
$(a)$ Bacteria: Many bacteria like $Rhizobium$ (symbiotic) and $Azospirillum$ (free-living) fix atmospheric nitrogen.
$(b)$ Cyanobacteria: These are autotrophic microbes widely distributed in aquatic and terrestrial environments,many of which can fix atmospheric nitrogen,$e.g.$,$Nostoc$,$Anabaena$,and $Oscillatoria$.
$(c)$ Fungi: Many members of the genus $Glomus$ form symbiotic associations with plants known as mycorrhiza. The fungal symbiont in these associations absorbs phosphorus from the soil and passes it to the plant.
$(d)$ Protists: Protists are not typically used as biofertilisers.
Therefore,the main sources of biofertilisers are bacteria,cyanobacteria,and fungi. The correct option is $(a), (b), (c)$.

(B) In paddy (rice) fields,$BGA$ (Blue-Green Algae),such as $Anabaena$ and $Nostoc$,serve as important biofertilisers.
These organisms are capable of fixing atmospheric nitrogen,which enhances the fertility of the soil and promotes the growth of the rice crop.

(A) Biofertilisers are organisms that enrich the nutrient quality of the soil.
Main sources of biofertilisers are bacteria,fungi,and cyanobacteria.
$Rhizobium$ is a symbiotic nitrogen-fixing bacterium found in the root nodules of leguminous plants.
Other nitrogen-fixing bacteria include $Azospirillum$ and $Azotobacter$.
Blue-green algae (cyanobacteria) like $Anabaena$,$Nostoc$,and $Oscillatoria$ also fix atmospheric nitrogen.
Mycorrhiza is a symbiotic association between fungi (e.g.,$Glomus$) and roots of higher plants,which helps in phosphorus absorption.
Therefore,the correct group includes Blue-green algae,$Rhizobium$,other nitrogen-fixing bacteria,and mycorrhiza.

(A) The symbiotic association between fungi and the roots of higher plants is called $Mycorrhiza$.
Many members of the genus $Glomus$ form $Mycorrhiza$.
These fungi absorb phosphorus from the soil and pass it to the plant.
Plants provide the fungi with carbohydrates and a suitable environment for growth.

(B) Statement $(A)$ is False: Organic farming produces crops that are generally rich in proteins,not necessarily lipids,vitamins,or iron.
Statement $(B)$ is True: Organic farming relies on biofertilisers (like Rhizobium,Azospirillum,etc.) which enrich the soil with nutrients and increase fertility.
Statement $(C)$ is False: Organic farming explicitly avoids the use of synthetic chemical fertilisers and pesticides.
Statement $(D)$ is True: Organic farming involves raising crops without synthetic chemicals by utilizing biological agents like bacteria,fungi,and cyanobacteria as biofertilisers and biopesticides.
Therefore,the correct sequence is $A-F, B-T, C-F, D-T$.

(B) $\rightarrow$ Some cyanobacteria live in a mutually beneficial relationship with plants,obtaining food and shelter while fixing nitrogen for the plant. They also reduce soil alkalinity and improve soil texture.
$\rightarrow$ $Nostoc$,$Anabaena$,and $Oscillatoria$ are Blue-Green Algae $(BGA)$ that can fix atmospheric nitrogen.
$\rightarrow$ In paddy fields,cyanobacteria serve as an important biofertilizer.
$\rightarrow$ $BGA$ also add organic matter to the soil and increase its fertility.

(D) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$1$. Bacteria: Many bacteria like $Rhizobium$ (in root nodules of legumes),$Azospirillum$,and $Azotobacter$ fix atmospheric nitrogen.
$2$. Fungi: Many members of the genus $Glomus$ form mycorrhiza,which absorbs phosphorus from the soil and passes it to the plant.
$3$. Cyanobacteria: Many cyanobacteria like $Anabaena$,$Nostoc$,and $Oscillatoria$ are autotrophic microbes that fix atmospheric nitrogen,especially in paddy fields.
Since all three groups act as biofertilizers,the correct answer is $D$.

(D) $Glomus$ is a genus of arbuscular mycorrhizal fungi $(AMF)$.
These fungi form symbiotic associations with the roots of higher plants.
The fungal hyphae absorb phosphorus from the soil and pass it to the plant,while the plant provides the fungi with carbohydrates.
Therefore,$Glomus$ is classified as a genus of fungi.

(A) Cyanobacteria (such as Anabaena and Nostoc) are autotrophic microbes widely distributed in aquatic and terrestrial environments. In paddy fields,they serve as an important biofertilizer by fixing atmospheric nitrogen,which enriches the soil with nitrogenous compounds. While Azospirillum is also a biofertilizer,it is typically associated with grasses and cereal crops like maize and wheat,and Rhizobium is primarily associated with leguminous plants. Therefore,Cyanobacteria is the most characteristic biofertilizer for paddy fields.

(D) Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.
$1$. The fungal symbiont in these associations absorbs phosphorus from the soil and passes it to the plant.
$2$. These fungal hyphae also provide resistance to root-borne pathogens.
$3$. They also increase the plant's tolerance to salinity and drought.
Therefore,all the given options are correct functions performed by the fungus in a mycorrhizal association.

(C) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$Nostoc$ is a cyanobacterium that fixes atmospheric nitrogen.
$Mycorrhiza$ is a symbiotic association between a fungus and the roots of higher plants, which helps in phosphorus absorption.
$Rhizobium$ is a symbiotic bacterium that fixes atmospheric nitrogen in the root nodules of leguminous plants.
$Agrobacterium$ is a soil bacterium used primarily as a vector in genetic engineering (e.g., $Agrobacterium \text{ tumefaciens}$) to transfer genes into plants; it is not classified as a biofertilizer.

(A) Biofertilizers are organisms that enrich the nutrient quality of the soil.
$A$. $Azospirillum$ and $Rhizobium$ are bacteria that fix atmospheric nitrogen.
$B$. $Anabaena$ is a cyanobacterium (blue-green alga) that also fixes nitrogen.
$C$. $Mycorrhiza$ is a symbiotic association between a fungus and the roots of higher plants,making it a fungal biofertilizer,not a bacterial one.

(A) In $1885$,the German botanist $A.B. Frank$ coined the term 'mycorrhiza' (plural: mycorrhizae) to describe the symbiotic association between fungi and the roots of higher plants. He discovered that these structures act as biofertilizers by enhancing nutrient uptake,particularly phosphorus,from the soil for the host plant.

(A) $Nostoc$ is a genus of cyanobacteria that is commonly used as a bio-fertilizer in paddy fields.
It has the ability to fix atmospheric nitrogen into ammonia,which is then utilized by the rice plants for growth.
$Azotobacter$ is a free-living nitrogen-fixing bacterium used for various crops but not specifically for paddy.
$Rhizobium$ is used for leguminous plants.
$Chlorella$ is a green alga used as a food supplement or in wastewater treatment,not as a nitrogen-fixing bio-fertilizer.

(D) The correct statement is that many members of the genus $Glomus$ form mycorrhiza.
$1$. $Glomus$ is a fungal genus that forms a symbiotic association with plant roots known as mycorrhiza,which helps in the absorption of phosphorus from the soil.
$2$. $Azospirillum$ and $Azotobacter$ are free-living nitrogen-fixing bacteria,not symbiotic.
$3$. $Monascus$ $purpureus$ is a yeast used for the production of blood-cholesterol lowering statins,not for mycorrhiza.
$4$. Cyanobacteria like $Anabaena$ and $Nostoc$ are autotrophic,not heterotrophic,and are used as biofertilizers in paddy fields.

(B) The correct answer is $B$.
Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.
Many members of the genus $Glomus$ form mycorrhiza.
The fungal symbiont in these associations absorbs phosphorus from the soil and passes it to the plant.

(C) The correct answer is $C$.
Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.
Many members of the genus $Glomus$ form mycorrhiza.
The fungal symbiont in these associations absorbs phosphorus from the soil and passes it to the plant.

(B) $Nostoc$.
Biofertilizers are substances that contain microbes which help in promoting the growth of plants and trees by increasing the supply of essential nutrients.
Cyanobacteria like $Anabaena$,$Nostoc$,and $Oscillatoria$ are known to fix atmospheric nitrogen,thereby enriching the soil with nitrogenous compounds and restoring its fertility.