Macronutrients and Micronutrients — Revision Notes

⚡ 30-Second Revision

Macronutrients (>$10, ext{mmol kg}^{-1}$ dry wt): — N, P, K, Ca, Mg, S, (C, H, O)

* N: Proteins, nucleic acids, chlorophyll; older leaves chlorosis. * P: ATP, nucleic acids, phospholipids; dark green/purplish older leaves. * K: Stomata, enzyme activation, turgor; marginal necrosis older leaves. * Ca: Cell wall, membrane integrity; apical meristem necrosis, young leaves. * Mg: Chlorophyll (central atom), enzyme activator; interveinal chlorosis older leaves. * S: Cysteine, methionine, vitamins; young leaves chlorosis.

Micronutrients (<$10, ext{mmol kg}^{-1}$ dry wt): — Fe, Mn, Cu, Zn, B, Mo, Cl, Ni

* Fe: Chlorophyll formation, e- transport; interveinal chlorosis young leaves. * Mn: Water splitting, enzyme activator; interveinal chlorosis young leaves. * Cu: Plastocyanin, oxidase enzymes; dieback young shoots.

* Zn: Auxin synthesis, enzyme activator; little leaf, rosette. * B: Pollen germination, cell elongation, sugar translocation; apical meristem death. * Mo: Nitrogenase, nitrate reductase; whiptail disease.

* Cl: Water splitting, anion-cation balance; wilting, chlorosis. * Ni: Urease enzyme; urea toxicity.

2-Minute Revision

Essential mineral elements are categorized into macronutrients and micronutrients based on the quantity required by plants. Macronutrients like Nitrogen (N), Phosphorus (P), and Potassium (K) are needed in large amounts and are crucial for structural components, energy transfer, and osmotic regulation.

N is vital for proteins and chlorophyll, P for ATP and nucleic acids, and K for stomatal movement. Their deficiencies often appear on older leaves due to mobility. Micronutrients such as Iron (Fe), Manganese (Mn), and Molybdenum (Mo) are required in smaller quantities, primarily acting as enzyme cofactors.

Fe is essential for chlorophyll formation and electron transport, Mn for water photolysis, and Mo for nitrogen fixation. Deficiencies of these often appear on younger leaves due to their immobility. Understanding these roles and the location of deficiency symptoms is key for NEET, as questions frequently test these associations.

5-Minute Revision

Plants require 17 essential mineral elements for their growth and development, classified by their quantitative need. Macronutrients (N, P, K, Ca, Mg, S, C, H, O) are needed in quantities greater than $10,\text{mmol kg}^{-1}$ of dry matter.

Nitrogen (N) is a major component of proteins, nucleic acids, and chlorophyll; its deficiency causes chlorosis of older leaves. Phosphorus (P) is crucial for ATP, nucleic acids, and root development; deficiency leads to dark green/purplish older leaves.

Potassium (K) regulates stomata and activates enzymes; deficiency causes marginal necrosis of older leaves. Calcium (Ca) strengthens cell walls and maintains membrane integrity; its deficiency affects young leaves and apical meristems.

Magnesium (Mg) is the central atom of chlorophyll and an enzyme activator; deficiency causes interveinal chlorosis of older leaves. Sulfur (S) is found in amino acids like cysteine and methionine; its deficiency causes chlorosis of younger leaves.

Micronutrients (Fe, Mn, Cu, Zn, B, Mo, Cl, Ni) are required in quantities less than $10,\text{mmol kg}^{-1}$ of dry matter, often acting as enzyme cofactors. Iron (Fe) is essential for chlorophyll formation and electron transport; deficiency causes interveinal chlorosis of young leaves.

Manganese (Mn) is vital for the photolysis of water during photosynthesis; deficiency causes interveinal chlorosis of young leaves. Copper (Cu) is part of plastocyanin and oxidase enzymes; deficiency leads to dieback of young shoots.

Zinc (Zn) activates enzymes and is essential for auxin synthesis; deficiency causes 'little leaf' disease. Boron (B) is involved in pollen germination, cell elongation, and carbohydrate translocation; deficiency causes death of apical meristems.

Molybdenum (Mo) is a component of nitrogenase and nitrate reductase; deficiency causes 'whiptail disease' in cauliflower. Chlorine (Cl) assists in water splitting and osmotic balance. Nickel (Ni) is a component of urease.

Remember that deficiencies of mobile nutrients (N, P, K, Mg) show on older leaves, while immobile ones (Ca, S, Fe, Mn, B, Cu, Zn) show on younger leaves.

Prelims Revision Notes

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Essential Elements: — 17 elements are essential for most higher plants, fulfilling Arnon and Stout's criteria (direct metabolic involvement, irreplaceability, completion of life cycle).
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Macronutrients (>$10, ext{mmol kg}^{-1}$ dry wt): — N, P, K, Ca, Mg, S, (C, H, O).

* Nitrogen (N): Proteins, nucleic acids, chlorophyll. Deficiency: Older leaves chlorosis, stunted growth. Mobile. * Phosphorus (P): ATP, nucleic acids, phospholipids. Deficiency: Dark green/purplish older leaves, stunted growth.

Mobile. * Potassium (K): Stomata regulation, enzyme activation, turgor. Deficiency: Marginal necrosis older leaves, weak stems. Mobile. * Calcium (Ca): Cell wall (middle lamella), membrane integrity.

Deficiency: Apical meristem necrosis, young leaves deformed. Immobile. * Magnesium (Mg): Central atom of chlorophyll, enzyme activator. Deficiency: Interveinal chlorosis older leaves. Mobile. * Sulfur (S): Cysteine, methionine, vitamins.

Deficiency: General chlorosis young leaves. Immobile.

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Micronutrients (<$10, ext{mmol kg}^{-1}$ dry wt): — Fe, Mn, Cu, Zn, B, Mo, Cl, Ni.

* Iron (Fe): Chlorophyll formation, e- transport (ferredoxin, cytochromes). Deficiency: Interveinal chlorosis young leaves. Immobile. * Manganese (Mn): Photolysis of water, enzyme activator.

Deficiency: Interveinal chlorosis young leaves, 'marsh spot'. Immobile. * Copper (Cu): Plastocyanin, oxidase enzymes. Deficiency: Dieback young shoots, necrosis leaf tips. Immobile. * Zinc (Zn): Auxin synthesis, enzyme activator (carbonic anhydrase).

Deficiency: 'Little leaf', rosette formation. Immobile. * Boron (B): Pollen germination, cell elongation, carbohydrate translocation. Deficiency: Apical meristem death, 'heart rot'. Immobile. * Molybdenum (Mo): Nitrogenase, nitrate reductase.

Deficiency: 'Whiptail disease' (cauliflower), N-deficiency symptoms. Immobile. * Chlorine (Cl): Water splitting, anion-cation balance. Deficiency: Wilting, chlorosis. * Nickel (Ni): Urease enzyme.

Deficiency: Urea toxicity.

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Nutrient Mobility: — Mobile nutrients (N, P, K, Mg) show deficiency on older leaves first. Immobile nutrients (Ca, S, Fe, Mn, B, Cu, Zn) show deficiency on younger leaves first.

Vyyuha Quick Recall

To remember Macronutrients: C. HOPKiNS CaFe Mg (C, H, O, P, K, N, S, Ca, Fe, Mg - though Fe is a micronutrient, it helps remember the list, then correct it).

To remember Micronutrients: 'Many CuZinCs BoMoNiCl' (Mn, Cu, Zn, B, Mo, Ni, Cl).

For deficiency symptoms on Older Leaves (Mobile): 'N-PK-Mg' (Nitrogen, Phosphorus, Potassium, Magnesium). For deficiency symptoms on Younger Leaves (Immobile): 'Ca-S-Fe-Mn-B-Cu-Zn-Mo' (Calcium, Sulfur, Iron, Manganese, Boron, Copper, Zinc, Molybdenum).