Which element acts as an activator for the enzyme 'Nitrogenase' involved in nitrogen fixation?
- Manganese
- Molybdenum
- Zinc
- Copper
Explanation: Molybdenum is a component of several enzymes, including nitrogenase and nitrate reductase, which are critical for nitrogen metabolism.
Which of the following is considered a 'Micronutrient' required by plants in very small amounts?
- Magnesium
- Molybdenum
- Phosphorus
- Potassium
Explanation: Micronutrients (trace elements) include Iron, Manganese, Copper, Molybdenum, Zinc, Boron, Chlorine, and Nickel. Phosphorus, Magnesium, and Potassium are macronutrients.
Which of the following is a criterion for the essentiality of a mineral element in plants according to Arnon and Stout?
- Must be present in detectable amounts in plant tissues
- Must enhance the general growth rate when supplied externally
- Requirement is specific and irreplaceable
- Must be required in relatively large quantities
Explanation: According to the Arnon-Stout criteria, an element is essential if: (1) the plant cannot complete its life cycle without it, (2) the requirement is specific and cannot be replaced by another element, and (3) it is directly involved in metabolism.
The primary cause of 'Manganese toxicity' is the reduced uptake of:
- Iron and Magnesium
- Nitrogen and Sulphur
- Potassium and Boron
- Copper and Zinc
Explanation: Manganese competes with Iron and Magnesium for uptake and with Magnesium for enzyme binding, inducing their deficiency symptoms.
The 'Middle Lamella', which holds plant cells together, is primarily composed of:
- Calcium pectate
- Sodium chloride
- Potassium nitrate
- Magnesium phosphate
Explanation: Calcium is used in the synthesis of cell walls, particularly as calcium pectate in the middle lamella. It is also required during the formation of mitotic spindles.
The localized death of tissue, particularly leaf tissue (Necrosis), is a classic symptom of the deficiency of:
- Molybdenum
- Calcium
- Nitrogen
- Iron
Explanation: Necrosis (death of tissue) is caused by the deficiency of Ca, Mg, Cu, and K. Calcium is essential for cell wall stability and middle lamella formation.
In the soil, the process of 'denitrification' is carried out by which bacteria?
- Pseudomonas
- Nitrosomonas
- Nitrobacter
- Rhizobium
Explanation: Denitrification, the conversion of nitrate to nitrogen gas, is carried out by bacteria such as Pseudomonas and Thiobacillus.
Which specific mineral is a core constituent of the ring structure of chlorophyll?
- Iron
- Calcium
- Manganese
- Magnesium
Explanation: Magnesium is the central atom of the chlorophyll molecule's porphyrin ring. It is also required for the activation of enzymes involved in respiration and photosynthesis.
Which mineral is involved in the synthesis of the 'mitotic spindle' during cell division?
- Sulphur
- Magnesium
- Phosphorus
- Calcium
Explanation: Calcium is required during cell division for the formation of the middle lamella and the organization of the mitotic spindle.
The 'Photolysis of water' during photosynthesis, which releases oxygen, requires which two minerals?
- Manganese and Chlorine
- Zinc and Copper
- Boron and Sulphur
- Magnesium and Iron
Explanation: Manganese ($Mn^{2+}$) and Chlorine ($Cl^-$) are essential for the water-splitting reaction in Photosystem II, which leads to the evolution of oxygen.
Which micronutrient is a component of Cytochromes and Ferredoxin, involved in electron transport?
Explanation: Iron is a constituent of proteins involved in the transfer of electrons like ferredoxin and cytochromes. It is reversibly oxidized from $Fe^{2+}$ to $Fe^{3+}$ during electron transfer.
The process of 'Transamination' involves the transfer of an amino group from:
- Acid to sugar
- Amide to protein
- Nitrate to ammonia
- Amino-acid to keto-acid
Explanation: Transamination is the transfer of an amino group from one amino acid to the keto group of a keto acid to form a new amino acid.
Which element was the last to be added to the list of essential plant mineral nutrients?
- Chlorine
- Molybdenum
- Nickel
- Boron
Explanation: Nickel is the 17th essential element, recognized for its role in the enzyme urease, which breaks down urea in plant tissues.
Which mineral plays a significant role in 'Redox reactions' and is a component of plastocyanin?
Explanation: Copper is essential for the overall metabolism in plants. It is associated with enzymes involved in redox reactions and is a component of plastocyanin in the ETC.
The 'Passive uptake' of minerals into the apoplast is generally:
- Rapid
- Against concentration
- Energy dependent
- Very slow
Explanation: Initial ion uptake into the apoplast (free space) is a rapid and passive process, while movement into the symplast is slower and active.
Amides like asparagine and glutamine are used for nitrogen transport in plants because they:
- Lack carbon atoms
- Have more nitrogen
- Are water insoluble
- Are highly toxic
Explanation: Amides contain a higher nitrogen-to-carbon ratio than amino acids, making them an efficient form for transporting nitrogen via the xylem.
The symbiotic bacterium 'Frankia' produces nitrogen-fixing nodules on the roots of:
- Non-leguminous plants
- Leguminous plants
- Aquatic ferns
- Cereal crops
Explanation: While Rhizobium is associated with legumes, Frankia forms nitrogen-fixing nodules on the roots of non-leguminous plants like Alnus.
The deficiency symptoms of which elements tend to appear first in young, developing leaves?
- Nitrogen
- Calcium
- Magnesium
- Potassium
Explanation: Elements like Calcium and Sulphur are relatively immobile and not exported from mature organs. Thus, their deficiency symptoms appear first in young tissues.
Which mineral is essential for the synthesis of Auxin, a primary plant growth hormone?
- Manganese
- Molybdenum
- Zinc
- Copper
Explanation: Zinc activates various enzymes like carboxylases and is essential for the biosynthesis of the plant growth regulator, Auxin (specifically Indole Acetic Acid).
The concentration of an essential element below which plant growth is retarded is termed as:
- Toxicity level
- Optimal concentration
- Flux rate
- Critical concentration
Explanation: The critical concentration is the specific level of a nutrient below which the plant shows deficiency symptoms and growth is significantly inhibited.
Which of the following elements is required for the structural integrity of the 'middle lamella'?
- Potassium
- Phosphorus
- Magnesium
- Calcium
Explanation: Calcium is a key component of calcium pectate, which forms the middle lamella that glues adjacent plant cells together.
Which mineral is a major constituent of the amino acids Cysteine and Methionine?
- Magnesium
- Phosphorus
- Nitrogen
- Sulphur
Explanation: Sulphur is present in two amino acids (cysteine and methionine) and is a main constituent of several coenzymes and vitamins like thiamine and biotin.
The movement of ions into or out of the plant cells is technically known as:
- Flux
- Osmosis
- Translocation
- Diffusion
Explanation: Flux refers to the rate of movement of ions. Inward movement into the cells is 'influx' and outward movement is 'efflux'.
Most minerals enter the root through active transport because:
- Membranes are porous
- Soil has more
- Ions are charged
- Water is less
Explanation: Minerals cannot move across cell membranes passively because they are charged particles (ions) and their concentration in the soil is usually lower than in the root.
Which of the following is an example of a mobile element within the plant body?
- Boron
- Sulphur
- Nitrogen
- Calcium
Explanation: Nitrogen, Potassium, and Magnesium are mobile; they are exported from old leaves to young ones. Calcium is immobile.
In the mechanism of mineral absorption, the 'Apoplast' refers to the movement through:
- Living cytoplasm
- Intercellular spaces
- Vacuolar membranes
- Plasmodesmata
Explanation: The apoplast is the non-living path involving cell walls and intercellular spaces. It is usually a rapid and passive process.
The 'pink' color found in the center of a functional legume root nodule is due to:
- Anthocyanin
- Cytochrome
- Chlorophyll
- Leghemoglobin
Explanation: Leghemoglobin is an oxygen scavenger that protects the oxygen-sensitive nitrogenase enzyme, giving functional nodules a pinkish hue.
Beneficial elements like Sodium, Silicon, Cobalt, and Selenium are particularly required by:
- Hydrophytes
- Lower algae
- All land plants
- Higher plants
Explanation: Apart from the 17 essential elements, some beneficial elements like Na, Si, Co, and Se are required by higher plants for specific physiological functions.
The 'Critical Concentration' for an element is the level below which:
- Growth is retarded
- Seedlings die
- Toxicity begins
- Metabolism stops
Explanation: Growth is significantly inhibited when the concentration of an essential element falls below its critical concentration.
Which of the following is a component of 'Nitrate Reductase'?
- Zinc
- Copper
- Iron
- Molybdenum
Explanation: Molybdenum is an essential cofactor for the enzymes nitrogenase and nitrate reductase.
Which element is involved in the 'anion-cation balance' and the opening of stomata?
- Sodium
- Magnesium
- Potassium
- Calcium
Explanation: Potassium ($K^+$) is the primary cation involved in osmotic regulation, turgor pressure, and the anionic balance within plant cells.
Which mineral is a constituent of the vitamins Thiamine, Biotin, and Coenzyme A?
- Sulphur
- Iron
- Magnesium
- Phosphorus
Explanation: Sulphur is an essential component of several vitamins and coenzymes, as well as the amino acids cysteine and methionine.
Which of the following elements is a component of energy-related chemical compounds in plants like ATP?
- Calcium
- Magnesium
- Phosphorus
- Potassium
Explanation: Phosphorus is a constituent of cell membranes, certain proteins, all nucleic acids, and nucleotides. It is required for all phosphorylation reactions (e.g., ATP).
Which element is essential for the stabilization of the 'ribosome' structure?
- Potassium
- Calcium
- Magnesium
- Iron
Explanation: Magnesium ions play a crucial role in binding the subunits of ribosomes together, which is necessary for protein synthesis.
Which mineral is required for the activation of the enzymes 'Rubisco' and 'Pepcase'?
- Calcium
- Zinc
- Manganese
- Magnesium
Explanation: Magnesium activates RuBP carboxylase-oxygenase (Rubisco) and Phosphoenolpyruvate carboxylase (Pepcase), both of which are critical in carbon fixation.
The energy-intensive process of fixing one molecule of $N_2$ into two molecules of ammonia requires:
- 16 ATP
- 8 ATP
- 2 ATP
- 32 ATP
Explanation: Nitrogen fixation is very expensive energetically; the reduction of one molecule of $N_2$ requires 16 molecules of ATP (8 ATP per ammonia produced).
In hydroponics, the nutrient solution must be 'adequately aerated' to ensure:
- Stomatal closure
- Optimum growth
- Sugar production
- Light absorption
Explanation: Adequate aeration of the nutrient solution is necessary for the roots to respire. Without oxygen, root metabolism slows down, hindering nutrient uptake and growth.
The technique of growing plants in a nutrient solution without soil was first demonstrated by:
- Arnon and Stout
- Melvin Calvin
- Julius von Sachs
- Hans Krebs
Explanation: In 1860, German botanist Julius von Sachs demonstrated for the first time that plants could be grown to maturity in a defined nutrient solution in the complete absence of soil.
Which mineral is essential for the activation of 'alcohol dehydrogenase'?
- Zinc
- Manganese
- Iron
- Copper
Explanation: Zinc is an activator for alcohol dehydrogenase and is essential for the synthesis of auxins.
Which enzyme is responsible for the oxidation of ammonia to nitrite in the soil?
- Nitrobacter
- Nitrosomonas
- Nitrate reductase
- Nitrogenase
Explanation: Nitrification is a two-step process: Ammonia is oxidized to nitrite by Nitrosomonas/Nitrococcus, then nitrite to nitrate by Nitrobacter.
Which element is part of 'Plastocyanin' and is involved in redox reactions?
- Zinc
- Iron
- Manganese
- Copper
Explanation: Copper is a component of plastocyanin, a protein involved in electron transport during photosynthesis.
The deficiency of which element leads to the inhibition of cell division in plants?
- Ca, Mg, B, Cl
- Fe, Mn, Cu, Zn
- P, Si, Na, Se
- N, K, S, Mo
Explanation: Low levels of Nitrogen, Potassium, Sulphur, and Molybdenum are known to inhibit cell division, leading to stunted growth.
In the process of 'Reductive Amination', ammonia reacts with which acid to form Glutamic acid?
- Oxaloacetic acid
- Citric acid
- Malic acid
- Alpha-ketoglutaric acid
Explanation: Ammonia reacts with alpha-ketoglutaric acid in the presence of NADPH and glutamate dehydrogenase to produce glutamic acid.
Which part of the plant is primarily responsible for the translocation of minerals from roots to leaves?
- Xylem
- Phloem
- Pith
- Epidermis
Explanation: Minerals are translocated through the xylem along with the ascending stream of water (transpiration pull) in the form of xylem sap.
The loss of chlorophyll leading to yellowing in leaves (Chlorosis) is caused by the deficiency of:
- Silicon and Cobalt
- Calcium and Boron
- Copper and Zinc
- Nitrogen and Iron
Explanation: Chlorosis is caused by the deficiency of N, K, Mg, S, Fe, Mn, Zn, and Mo. Nitrogen is a structural component, while Iron acts as a catalyst in chlorophyll synthesis.
A mineral is considered 'Toxic' if it reduces the dry weight of tissues by about:
- Twenty-five percent
- Fifty percent
- Ten percent
- Two percent
Explanation: Any mineral ion concentration in tissues that reduces the dry weight of tissues by about 10 percent is considered toxic.
Which mineral element is required by plants for the maintenance of the ribosome structure?
- Potassium
- Magnesium
- Sulphur
- Phosphorus
Explanation: Magnesium ions help in binding ribosome subunits together, thus maintaining the overall structure of ribosomes during protein synthesis.
Excessive intake of Manganese can induce the deficiency of which other minerals?
- Iron, Magnesium and Calcium
- Copper and Zinc
- Boron and Chlorine
- Nitrogen and Potassium
Explanation: Manganese toxicity symptoms are actually the induced deficiencies of Fe, Mg, and Ca. Mn competes with Fe and Mg for uptake and with Mg for binding with enzymes, and it also inhibits Calcium (Ca) translocation in the shoot apex. Prominent visual symptoms include brown spots surrounded by chlorotic veins.
Which micronutrient is required in the largest amount compared to other micronutrients?
- Zinc
- Molybdenum
- Copper
- Iron
Explanation: Plants require iron in larger amounts than other micronutrients. It is a vital constituent of proteins like ferredoxin and cytochromes.
Which mineral is required for the 'germination of pollen' grains?
- Zinc
- Molybdenum
- Chlorine
- Boron
Explanation: Boron is necessary for pollen germination, cell elongation, and the translocation of carbohydrates.
Plants like 'Soybean' export the fixed nitrogen from nodules primarily as:
- Ureides
- Amino acids
- Nitrate ions
- Ammonia gas
Explanation: Soybeans export fixed nitrogen as ureides (allantoin/allantoic acid), which have a very high nitrogen-to-carbon ratio.
Which of the following is NOT a macronutrient?
- Carbon
- Manganese
- Hydrogen
- Oxygen
Explanation: Macronutrients include C, H, O, N, P, K, S, Ca, and Mg. Manganese is a micronutrient.
The conversion of atmospheric nitrogen ($N_2$) into ammonia by living organisms is termed as:
- Denitrification
- Biological nitrogen fixation
- Nitrification
- Ammonification
Explanation: Biological nitrogen fixation is the process where specific prokaryotes reduce atmospheric nitrogen to ammonia using the enzyme nitrogenase.
The translocation of carbohydrates (sugars) through the phloem is specifically facilitated by:
Explanation: Boron is required for calcium uptake, pollen germination, cell elongation, and notably, for the translocation of carbohydrates in plants.
Which of the following is a free-living nitrogen-fixing aerobic bacterium?
- Rhodospirillum
- Azotobacter
- Frankia
- Rhizobium
Explanation: Azotobacter and Beijerinckia are free-living aerobic nitrogen-fixing bacteria. Rhodospirillum is free-living but anaerobic.
The deficiency of which elements is known to 'delay flowering' in several plant species?
- B, Cl, Ni
- N, S, Mo
- Ca, Mg, Cu
- Fe, Mn, Zn
Explanation: Low levels of Nitrogen, Sulphur, and Molybdenum cause a delay in flowering in plants. These elements are critical for the transition from vegetative to reproductive phases.
The 'passive phase' of ion uptake usually occurs through which part of the cell?
- Vacuole
- Inner space
- Nucleus
- Outer space
Explanation: The initial rapid uptake of ions into the 'free space' or 'outer space' (apoplast) of cells is passive, while the subsequent uptake into the 'inner space' (symplast) is active.
Atmospheric nitrogen can be fixed by which non-biological physical process?
- Tidal waves
- High rainfall
- Lightning
- Volcanic eruption
Explanation: Lightning and UV radiation provide enough energy to convert atmospheric nitrogen into nitrogen oxides ($NO$, $NO_2$, $N_2O$).
Which mineral is essential for maintaining the turgidity of cells and the opening and closing of stomata?
- Magnesium
- Calcium
- Potassium
- Phosphorus
Explanation: Potassium ($K^+$) helps in maintaining an anion-cation balance in cells and is involved in protein synthesis and the opening and closing of stomata via turgor changes.
The translocation of mineral salts takes place through the xylem via:
- Root pressure
- Transpiration pull
- Active pumping
- Cytoplasmic streaming
Explanation: Minerals are carried along with the ascending stream of water through the xylem, driven largely by the transpiration pull.