Part 3 — Functions of Essential Elements, Deficiency Symptoms, Mobility/Immobility (Q51–75)

Q51.

Which element is a structural component of the middle lamella in plant cell walls?
A. Magnesium
B. Calcium ✅
C. Iron
D. Potassium

Explanation:

A. Mg is central in chlorophyll and enzyme activator.
B. (Correct) Calcium forms calcium pectate in middle lamella, providing rigidity and adhesion.
C. Iron is involved in electron transport.
D. K regulates osmotic balance, not wall structure.

Q52.

Nitrogen is essential because it is a component of:
A. Cellulose and lignin
B. Chlorophyll, amino acids, nucleotides ✅
C. Cutin and suberin
D. Secondary metabolites only

Explanation:

A. Cellulose/lignin are C-based polymers, not N.
B. (Correct) Nitrogen is in proteins (amino acids), nucleic acids (DNA/RNA), chlorophyll, hormones, coenzymes.
C. Cutin/suberin are fatty substances.
D. N is in both primary and secondary metabolites.

Q53.

Which deficiency causes chlorosis in older leaves first?
A. Calcium
B. Iron
C. Nitrogen ✅
D. Boron

Explanation:

A/B/D. Ca, Fe, B are immobile → symptoms in young leaves.
C. (Correct) Nitrogen is mobile, deficiency symptoms start in older leaves (yellowing/chlorosis).

Q54.

Which nutrient deficiency results in necrosis of leaf margins?
A. Potassium ✅
B. Phosphorus
C. Iron
D. Sulphur

Explanation:

A. (Correct) K deficiency leads to scorching/necrosis at leaf margins.
B. P deficiency causes stunted growth, purpling.
C. Fe deficiency → interveinal chlorosis in young leaves.
D. Sulphur deficiency → general chlorosis like N but in young leaves.

Q55.

Which essential element is required for water-splitting during photosynthesis?
A. Manganese ✅
B. Magnesium
C. Calcium
D. Boron

Explanation:

A. (Correct) Mn is part of the oxygen-evolving complex (OEC) in PSII, splits water during photolysis.
B. Mg central in chlorophyll, not water-splitting.
C. Ca is involved in OEC stabilization but not main catalytic element.
D. Boron regulates cell wall and sugar transport.

Q56.

Which element deficiency leads to “whiptail disease” in cauliflower?
A. Boron
B. Molybdenum ✅
C. Zinc
D. Copper

Explanation:

A. Boron deficiency → heart rot in sugar beet.
B. (Correct) Mo deficiency causes whiptail in cauliflower, due to impaired nitrate reduction.
C. Zn deficiency → khaira disease in rice.
D. Cu deficiency affects lignin formation.

Q57.

Which nutrient deficiency leads to “little leaf disease” in plants?
A. Zinc ✅
B. Boron
C. Magnesium
D. Potassium

Explanation:

A. (Correct) Zn deficiency leads to reduced auxin synthesis → small, distorted leaves (little leaf disease).
B/C/D. Other deficiencies show different symptoms.

Q58.

Iron deficiency shows first in young leaves because:
A. It is mobile and translocated
B. It is immobile in phloem ✅
C. It is stored in roots
D. It is abundant in chlorophyll

Explanation:

A. Wrong, Fe is immobile.
B. (Correct) Iron is immobile in plants → new leaves cannot get enough → chlorosis in young tissues first.
C. Not stored extensively.
D. Iron is not part of chlorophyll structure but required for its synthesis.

Q59.

Which deficiency symptom is wrongly matched?
A. Nitrogen – general chlorosis
B. Potassium – necrosis at margins
C. Iron – interveinal chlorosis in old leaves ✅
D. Magnesium – interveinal chlorosis in older leaves

Explanation:

A/B/D. Correct matches.
C. (Correct) Iron deficiency occurs in young leaves, not old leaves (Fe is immobile).

Q60.

Deficiency of which element causes death of root tips?
A. Calcium ✅
B. Nitrogen
C. Sulphur
D. Magnesium

Explanation:

A. (Correct) Ca is immobile, essential for cell wall/membrane stability and meristematic growth → deficiency kills root tips.
B-D. Don’t directly kill meristems.

Q61.

Mobile nutrients in plants include:
A. N, P, K ✅
B. Ca, Fe, B
C. Mn, Cu, Zn
D. Mo, B, Ca

Explanation:

A. (Correct) N, P, K are mobile, deficiency symptoms first appear in older leaves.
B-D. Ca, Fe, B, etc. are immobile → symptoms in young leaves.

Q62.

Sulphur deficiency symptoms resemble nitrogen deficiency except they occur in:
A. Old leaves
B. Young leaves ✅
C. Roots
D. Flowers

Explanation:

A. N deficiency = old leaves.
B. (Correct) S deficiency = young leaves (immobile).
C/D. Not primary symptoms.

Q63.

Zinc plays an important role in:
A. Chlorophyll synthesis
B. Auxin synthesis ✅
C. Water-splitting
D. Cell wall pectin

Explanation:

A. Mg/Fe roles.
B. (Correct) Zn is cofactor in tryptophan → IAA synthesis pathway.
C. Mn in photolysis.
D. Ca in wall.

Q64.

Which element deficiency causes hollow heart disease in groundnut and sugar beet?
A. Zinc
B. Boron ✅
C. Copper
D. Iron

Explanation:

A/C/D. Not correct.
B. (Correct) Boron deficiency affects carbohydrate transport → hollow heart in beets/groundnut.

Q65.

“Dieback” disease of citrus is caused by deficiency of:
A. Copper ✅
B. Magnesium
C. Nitrogen
D. Sulphur

Explanation:

A. (Correct) Cu deficiency → dieback, stem rotting, defective lignification.
B/C/D. Not the cause of dieback.

Q66.

Magnesium deficiency causes interveinal chlorosis in older leaves because:
A. It is immobile
B. It is mobile and remobilized to young tissues ✅
C. It accumulates in roots
D. It is stored in middle lamella

Explanation:

A. Wrong — immobile nutrients affect young leaves.
B. (Correct) Mg is mobile → remobilized to young leaves → older leaves become deficient → interveinal chlorosis.
C/D. Not true.

Q67.

Which deficiency is responsible for delayed flowering and anthocyanin accumulation (purple leaves)?
A. Phosphorus ✅
B. Potassium
C. Iron
D. Calcium

Explanation:

A. (Correct) P deficiency → stunted growth, delayed flowering, purpling (anthocyanin).
B/C/D. Different symptoms.

Q68.

Chlorosis is a general deficiency symptom caused by lack of all except:
A. N
B. Mg
C. Fe
D. Ca ✅

Explanation:

A-C. N, Mg, Fe are directly required for chlorophyll synthesis/function.
D. (Correct) Ca deficiency doesn’t cause chlorosis but necrosis/death of meristems.

Q69.

Deficiency of which element reduces biological nitrogen fixation in legumes?
A. Mo and Fe ✅
B. Ca and B
C. K and Mg
D. Cu and Zn

Explanation:

A. (Correct) Mo and Fe are essential cofactors of nitrogenase enzyme.
B/C/D. Important for other functions but not nitrogenase.

Q70.

Immobile nutrients are characterized by deficiency symptoms:
A. First in old leaves
B. First in young leaves ✅
C. Uniform across all leaves
D. Restricted to roots

Explanation:

A. Mobile nutrients → older leaves first.
B. (Correct) Immobile nutrients → deficiency symptoms in young tissues.
C/D. Not accurate.

Q71.

Boron deficiency mainly affects:
A. Chlorophyll synthesis
B. Cell wall formation and pollen germination ✅
C. Stomatal regulation
D. Photolysis of water

Explanation:

A. N, Mg, Fe more critical.
B. (Correct) Boron = important for cell wall integrity, pollen tube growth.
C. K⁺ regulates stomata.
D. Mn catalyzes photolysis.

Q72.

Critical concentration is:
A. Minimum concentration of nutrient needed for visible growth ✅
B. Maximum concentration beyond which toxicity appears
C. Average concentration in soil
D. Stored nutrient reserve

Explanation:

A. (Correct) Critical concentration = minimum nutrient concentration required for normal growth. Below this, deficiency symptoms appear.
B. Refers to toxicity threshold.
C/D. Not correct.

Q73.

Which deficiency causes browning of leaf tips and poor seed/fruit development?
A. Boron ✅
B. Iron
C. Sulphur
D. Potassium

Explanation:

A. (Correct) B deficiency = browning of tips, necrosis, poor seed/fruit set.
B/C/D. Different symptoms.

Q74.

Deficiency of which element causes black necrotic spots due to impaired lignification?
A. Boron
B. Copper ✅
C. Molybdenum
D. Magnesium

Explanation:

A. Sugar transport issues.
B. (Correct) Cu deficiency → poor lignification → necrotic spots.
C. Whiptail in cauliflower.
D. Chlorosis in older leaves.

Q75.

Which set correctly matches mobile vs immobile nutrients?
A. Mobile – N, P, K; Immobile – Ca, B, Fe ✅
B. Mobile – Fe, Ca; Immobile – N, P
C. Mobile – Mo, Cu; Immobile – K, Mg
D. Mobile – B, Ca; Immobile – N, P

Explanation:

A. (Correct) Mobile nutrients: N, P, K, Mg. Immobile: Ca, B, Fe.
B-D. Mismatched.

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Part 3 — Functions of Essential Elements, Deficiency Symptoms, Mobility/Immobility (Q51–75)