Mineral nutrition practice · Mixed difficulty

Option D (Phosphorus) is correct because phosphorus deficiency can lead to premature leaf fall in plants due to its role in energy transfer and overall plant health.

Option B (Metabolic energy) is correct because the symplast pathway involves crossing cell membranes, which requires energy for active transport of ions.

Option A (Protonated) is correct because ammonia ($NH_3$) accepts a proton ($H^+$) to form the ammonium ion ($NH_4^+$) at physiological pH.

Option D (Carnation) is correct because carnations are a popular and commercially viable flower crop often grown using hydroponic techniques.

Option D (${N_2}$ - fixation) is correct because leghaemoglobin production is induced in response to nitrogen fixation in root nodules.

Option D (All of these) is correct because Lead (Pb), Cobalt (Co), and Uranium (U) are all heavy metals that can have harmful effects on biological systems, including plants and animals, when present in excessive amounts.

Option C (Activates catalase) is correct because Iron (Fe), not Boron (B), is a component and activator of catalase.

Option C (Only a and c are correct) is correct because both Rhizobium and Frankia are heterotrophic and symbiotic nitrogen-fixing bacteria.

Option B is correct because the 'nif' gene (nitrogen fixation gene) is responsible for encoding the enzymes, including nitrogenase, required for biological nitrogen fixation.

Option D (I and IV) is correct because nitrogen is primarily required by meristematic tissues for cell division and metabolically active cells for protein and nucleic acid synthesis.

Option C (Zn – Synthesis of cytochromes) is correct because Zinc is involved in the synthesis of auxin and activation of enzymes, not cytochromes, which require iron.

Option C (Triple covalent bond) is correct because molecular nitrogen ($N_2$) has a strong triple covalent bond between the two nitrogen atoms.

Option A (Passive uptake may be non-mediated or mediated) is correct because passive uptake can occur through simple diffusion (non-mediated) or through ion channels (mediated).

Option B (6) is correct because each $N_2$ molecule produces two $NH_3$ molecules, so three $N_2$ molecules produce six $NH_3$ molecules.

Option D (Application of iron and magnesium to promote synthesis of chlorophyll) is correct because premature yellowing suggests chlorophyll deficiency, which can be addressed by providing iron and magnesium, essential components for chlorophyll synthesis.

Option A (Chelate metals) is correct because chelating agents are used in hydroponics to bind to metal ions, preventing them from precipitating and making them more available to plants.

Option B is correct because both the assertion and reason are true, but the reason does not explain the assertion. The entry of ions from soil to outer space is passive, and ion carriers are for active uptake.

Option D (I, II and III) is correct because essential elements play roles in cell membrane permeability, osmotic concentration, and as constituents of macromolecules and coenzymes.

Option B (Rapidly) is correct because the initial phase of mineral absorption is characterized by a rapid uptake of ions into the apoplast.

Option B ((i), (ii), (iv)) is correct because these statements accurately describe aspects of plant nutrition and essential elements.

Option B (Nitrobacter) is correct because Nitrobacter is responsible for converting nitrite to nitrate during nitrification.

Option B (Denitrification) is correct because denitrification is the process where nitrates are converted back into atmospheric nitrogen.

Option B (Passive uptake) is correct because the first phase of mineral absorption is rapid and does not require energy, indicating passive transport.

Option B (N) is correct because nitrogen is a major constituent of proteins, nucleic acids, vitamins, and hormones.

Option D (All of these) is correct because nitrification involves the conversion of ammonia to nitrite and then nitrite to nitrate.

Option B (Upon successful infection of the root hair) is correct because curling of root hair occurs after Rhizobium successfully infects the root hair, initiating nodule formation.

Option C (Botanist) is correct because Julius Von Sachs was a German botanist who significantly contributed to plant physiology, including demonstrating hydroponics.

Option A (Bacillus polymixa) is correct because Bacillus polymixa is a free-living nitrogen-fixing bacteria.

Option C ($Fe$) is correct because Nitrogen (N), Phosphorus (P), and Potassium (K) are considered macronutrients or \"critical elements\" due to their high demand in plants, while Iron (Fe) is a micronutrient.

Option A (Only IV) is incorrect and Option C (IV and II) is also incorrect. The correct answer is weathering of rocks. Soil maintains a regular supply of minerals primarily through the weathering of rocks, which releases minerals into the soil. While activity of decomposers is important for nutrient cycling, it doesn't maintain a *regular* supply of minerals in the same way that weathering does. Slow vegetation is not a factor in maintaining mineral supply. Therefore, none of the provided options are fully correct, but weathering of rocks is the closest single correct answer. Since the question forces a choice, we must select the best available option, which is A (Only IV).