183-190 Flashcards
What are bio-fertilizers?
Preparations containing microorganisms that supply nutrients like nitrogen and phosphorus.
How do bio-fertilizers work?
They increase the microbial population
What are the types of nitrogen-fixing microbes?
Free-living
Name an aerobic free-living nitrogen fixer.
Azotobacter chroococcum (used for wheat
Which bacteria is anaerobic and fixes nitrogen?
Clostridium species.
Which microbe is associated symbiotically with grasses?
Azospirillum (used for sorghum
What is a nodule-forming nitrogen fixer?
Rhizobium spp.
What is the function of Rhizobium in legumes?
It fixes atmospheric nitrogen symbiotically in root nodules.
What is a non-nodulating symbiotic nitrogen fixer?
Anabaena azollae
What is the function of actinomycetes in nitrogen fixation?
Frankia species fix nitrogen in symbiosis with Casuarina and alder trees.
What is the nitrogen contribution of Blue Green Algae (BGA) in rice fields?
BGA can add up to 20-25 kg N/ha.
How does Rhizobium impact crop yield?
It increases yield by 25-30% in succeeding crops.
What are the primary soil microorganisms?
Bacteria
What pH range is preferred by fungi in soil?
4.5 to 6.5 (acidic).
What type of soil favors actinomycetes growth?
Slightly alkaline soils.
What is the general order of microbial abundance in soil?
Bacteria > Actinomycetes > Fungi > Algae.
What happens in acidic soils to microbial populations?
Fungi dominate over bacteria and actinomycetes.
What is the most abundant microorganism in soil?
Bacteria (10⁶ - 10⁹ per gram of soil).
What is the main role of protozoa in soil?
They control bacterial populations.
Name an indicator plant for nitrogen deficiency.
Cauliflower and cabbage.
Which plants indicate potassium deficiency?
Sunflower and sorghum.
What are macro-nutrients in plants?
Nutrients required in concentrations >100 ppm (e.g.
What are micro-nutrients in plants?
Nutrients required in <100 ppm (e.g.
What are the immobile nutrients in plants?
Calcium (Ca) and Boron (B).
Who proposed the 16 essential plant nutrients?
Arnon & Stout.
What is the 17th essential plant nutrient discovered?
Nickel (Ni)
What does Liebig’s Law of Minimum state?
Plant growth is limited by the least available nutrient.
What are beneficial nutrients?
Vanadium (V)
Who introduced the term “functional nutrients”?
D. J. Nicholas in 1963.
What is the role of nitrogen in plants?
It promotes vegetative growth and is a key part of proteins and chlorophyll.
What is a common nitrogen deficiency symptom?
Yellowing of lower leaves (chlorosis).
What is a disease caused by nitrogen deficiency?
Buttoning in cauliflower.
How does phosphorus benefit plants?
It supports root development
What is a phosphorus deficiency symptom?
Purple coloration on older maize leaves.
Why is phosphorus called the “key of life”?
A plant cannot complete its life cycle without it.
What is the function of potassium in plants?
Stomatal regulation
What is a key potassium deficiency symptom?
Dead tissue spots at leaf tips.
What is calcium’s role in plants?
It is a key component of cell walls.
What happens in calcium deficiency?
Terminal bud death and leaf scorching.
Why is magnesium important for plants?
It is a central atom in chlorophyll.
What is a magnesium deficiency symptom?
Mottled and chlorotic leaves.
What is sulfur’s role in plants?
It is a component of amino acids like cysteine and methionine.
What is the sulfur deficiency symptom?
Pale green young leaves.
Name a sulfur-oxidizing bacteria.
Thiobacillus species.
What is the function of iron in plants?
Essential for nitrogen fixation and enzyme activity.
What is a major iron deficiency symptom?
Interveinal chlorosis while main veins remain green.
What is manganese’s role in plants?
Formation of chlorophyll and enzyme co-factor.
What is a manganese toxicity effect?
Crinkled leaves in cotton.
What is a major manganese deficiency symptom?
Dead spots on leaves with smaller veins remaining green.
Name a disease caused by manganese deficiency.
Pahala blight of sugarcane.
What is the primary function of copper in plants?
It is a component of plastocyanin
What is a copper deficiency symptom?
Chlorosis at the tips and margins of young leaves.
What is zinc’s role in plants?
It is essential for enzyme activation and growth regulation.
What are zinc deficiency symptoms?
Rosetting and interveinal chlorosis.
What is a disease caused by zinc deficiency?
Khaira disease in rice.
Why is boron essential for plants?
It aids in pollen germination
What is a common boron deficiency symptom?
Hollow stem in cauliflower.
Name a disease caused by boron deficiency.
Fruit cracking in tomato and pomegranate.
What is cobalt’s function in plants?
It is essential for nitrogen fixation and a component of vitamin B12.
What is a molybdenum deficiency symptom?
Whiptail in cauliflower.
How is molybdenum absorbed by plants?
As molybdate (MoO₄²⁻).
What enzyme requires molybdenum for nitrogen metabolism?
Nitrate reductase.
What is chlorine’s role in plants?
It functions in osmoregulation and disease resistance.
What is a high chlorine-sensitive crop?
Legumes and tobacco.
What is the function of sodium in plants?
It aids in osmoregulation and is essential for CAM plants.
What is a symptom of sodium deficiency?
Reduced drought tolerance in sugar beet.
What is a key function of silicon in plants?
It strengthens cell walls and improves disease resistance.
Which crops require silicon?
Rice and maize.
What is an effect of silicon deficiency?
Increased susceptibility to fungal infections.
What is metabolic transformation in plants?
Conversion of inorganic nutrients into organic compounds.
What is a pedologic soil layer?
A surface layer cemented by calcium and magnesium carbonates.
What is black heart disease in potatoes caused by?
Oxygen deficiency.
What is soil erodibility?
The susceptibility of soil to erosion.
What is soil erosivity?
The capacity of an agent (like wind or water) to cause erosion.
What is soil erodibility factor (K)?
A measure of soil loss under a standard condition.
What is a colloidal particle?
A particle smaller than 1 µm in diameter.
What is the size range of colloidal solution particles?
10⁻⁹ to 10⁻⁶ meters.
What is a micelle in soil science?
An individual colloidal particle with negative surface charges.
What is the order of cation adsorption in soil?
Al³⁺ > H⁺ > Ca²⁺ > Mg²⁺ > K⁺ > Na⁺.
What is the key function of phosphorus in plants?
Energy storage and transfer (ATP
What is an indicator plant for calcium deficiency?
Sunflower.
What is the primary role of potassium in plants?
Regulation of stomatal movement.
What is the term for excess nutrient absorption by plants?
Luxury consumption.
What is the role of boron in reproduction?
It regulates sugar translocation and pollen germination.
What is the principal nitrogen-fixing enzyme?
Nitrogenase.
What is the key symptom of iron deficiency in plants?
Interveinal chlorosis while veins remain green.
What is the function of manganese in enzyme activation?
It acts as a cofactor in redox reactions.
What is the cause of marsh spot disease in peas?
Manganese deficiency.
What is the role of cobalt in legume nodules?
It is required for leghaemoglobin formation.
What is the effect of excess boron in plants?
Leaf tip necrosis and reduced growth.
What is an indicator of boron deficiency in citrus?
Dieback and fruit cracking.
What is the role of sodium in C4 plants?
It enhances photosynthetic efficiency.
What is a major symptom of copper deficiency?
Excess gumming (gummosis).
What does zinc deficiency cause in citrus?
Mottled leaf disorder.
What is the function of nickel in plants?
It is essential for urease enzyme activity.
What is an indicator plant for boron deficiency?
Cauliflower (browning or hollow stem).
What is cat clay?
A clay-sulfate soil that turns extremely acidic when drained.
What is regosol?
A soil without distinct genetic horizons.
What is solum in soil science?
The combined A and B horizons of soil.
What is regolith?
The weathered upper layer of rock
What is soil colloid flocculation?
The process where soil particles aggregate due to cation presence.
What is the primary function of molybdenum in plants?
Enzyme activation for nitrogen metabolism.
What is the role of iron in respiration?
It acts as an oxygen carrier in leghaemoglobin.
What is the primary function of sulfur in oilseeds?
It enhances oil and protein content.
What is the function of chloride in plants?
Essential for osmotic balance and enzyme activation.
What is a key function of silicon in rice?
It strengthens plant cell walls and prevents lodging.
What does nitrogen deficiency cause in tobacco?
Sand drown disease.
What is an indicator plant for magnesium deficiency?
Tobacco (sand drown disease).
