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State Board · Class 12 · Biology

Lesson 7: Plant Growth and Mineral Nutrition

7 concepts · 56 practice questions with answers · Free to read

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Plant growth

Link to Std 9–10

The last lesson showed how water and minerals reach the leaves; here we see how a plant grows, which hormones control it and how it gets nitrogen.

From daily life

A seedling gains a few centimetres every week — but only near its tips.

Simple definition

Growth = permanent, irreversible increase in the bulk of an organism. In plants it occurs in meristems (indeterminate).

GrowthGrowth: meristems and the sigmoid curveApicalIntercalaryLateralLagLogStationaryApical: lengthIntercalary: internodeLateral: girth (cambium)Lag → log → stationaryGrand period = all phasesGrowth = permanent irreversible increase; indeterminate in root/stemPhases: cell division → enlargement (turgid) → maturationAGR = growth per unit time; RGR = relative to initial sizeArithmetic: Lt = L0 + rt (linear); geometric: W1 = W0·e^(rt)Factors: water, nutrients, 25–35 °C, O₂, light, gravity, hormonesCrescograph (J. C. Bose): magnifies growth 10,000 times

In the figure : Meristems, phases and the sigmoid curve.

Rule 1 : Meristems and phases of growth — Apical meristem (tips of root and shoot) = length; intercalary (base of internodes) = internode length; lateral (vascular cambium) = girth. Root and stem growth is indeterminate; leaves, flowers, fruits are determinate. Three phases: (A) cell division (thin walls, large nucleus; slow = lag), (B) cell enlargement (vacuole, turgid, new wall; fast = log), (C) maturation (specialisation; steady = stationary).

  • Easy : Apical = length; cambium = girth.
  • Medium : Lag slow, log fast.
  • Exam-type (CET) : Leaves: determinate.

Rule 2 : Growth rate, types and conditions — AGR (absolute growth rate) = total growth per unit time; RGR = growth relative to the initial size. Example (own): a 5 cm² leaf grows 5 cm²/day ⇒ RGR 100%; a 50 cm² leaf grows the same ⇒ RGR 10%. Arithmetic growth: constant rate (2, 4, 6, 8 cm), one daughter cell divides, the other matures; Lt = L0 + rt; linear graph. Geometric: both daughters divide; W1 = W0·e^(rt); exponential graph; together they give the sigmoid (S) curve; total time of all phases = grand period. Conditions: water, nutrients, 25–35 °C, O₂, light, gravity, hormones. Measured with auxanometer, crescograph (J. C. Bose; 10,000×).

  • Easy : RGR is higher in a small leaf.
  • Medium : Arithmetic = linear.
  • Exam-type (CET) : Sigmoid = lag + log + stationary.
Remember

Apical = height; lateral = girth.

Common mistake and CET trap

‘All organs grow indefinitely’ is wrong. Trap: ‘growth is fastest in lag phase’ is wrong.

Shortcut

Memory clue : "LLS = lag, log, stationary — the S-curve".

Spot the difference

TypeArithmeticGeometric
DivisionOne daughterBoth daughters
GraphLinearExponential

Practice questions

Easy
  1. 1Types of meristem?
  2. 2What increases girth?
  3. 3Log phase?
Medium
  1. 4RGR is?
  2. 5A 10 cm² leaf adds 5 cm²; RGR?
  3. 6Whose crescograph?
Challenging
  1. 7Grand period?
  2. 8Determinate growth in?
Show answers (try them yourself first)
  1. 1Apical, intercalary, lateral.
  2. 2Vascular cambium.
  3. 3Fast growth.
  4. 4Growth relative to initial size.
  5. 550%.
  6. 6J. C. Bose.
  7. 7Total time of all phases.
  8. 8Leaves, flowers, fruits.

Differentiation and plasticity

From daily life

Clay fired into a brick can't return to clay; a cell is similar.

Simple definition

Differentiation = permanent change in a cell for specialisation. Plasticity = ability to form different structures in different conditions.

DifferentiationDifferentiation and plasticityMeristem cellDifferentiatedDedifferentiationRedifferentiatione.g. interfascicular cambiumcork cambium ← parenchymaDifferentiation: permanent change, division ability lost (hydrophyte parenchyma)Dedifferentiation: living cell regains division (interfascicular, cork cambium)Redifferentiation: loses division again, takes a function (secondary xylem)Development = growth + morphogenesis + maturation + senescencePlasticity: different forms with conditions — heterophyllye.g. cotton, coriander (intrinsic); Ranunculus (environmental)Juvenile vs adult leaves; aquatic vs terrestrial leaves differ

In the figure : Differentiation, dedifferentiation and redifferentiation.

Rule 1 : The three terms — Differentiation: maturation of cells from root/shoot tips; permanent structural and functional change; division ability is lost; e.g. parenchyma of hydrophytes with large air spaces. Dedifferentiation: a living mature cell regains division (becomes meristematic); e.g. interfascicular cambium and cork cambium from parenchyma. Redifferentiation: cells so formed again lose division and take a function; e.g. secondary xylem.

  • Easy : Dedifferentiation = divides again.
  • Medium : Cork cambium = example.
  • Exam-type (CET) : Redifferentiation = secondary xylem.

Rule 2 : Development and plasticity — Development = ordered changes from germination to death/senescence: growth + morphogenesis + maturation + senescence. Plasticity: a plant forms different structures in response to internal/external cues. Heterophylly: different leaf shapes on one plant — juvenile vs adult (cotton, coriander, larkspur: intrinsic); aquatic vs terrestrial (Ranunculus: environmental).

  • Easy : Development includes growth and maturity.
  • Medium : Cotton: intrinsic.
  • Exam-type (CET) : Ranunculus: environmental.
Remember

De-diff = divide again; re-diff = settle to a role again.

Common mistake and CET trap

‘A mature cell can never divide’ is wrong (dedifferentiation). Trap: ‘heterophylly = different plants’ is wrong.

Shortcut

Memory clue : "D–D–R in order".

Spot the difference

TermDivision ability
DifferentiationLost
DedifferentiationRegained
RedifferentiationLost again

Practice questions

Easy
  1. 1What is differentiation?
  2. 2Cork cambium arises from?
  3. 3Interfascicular cambium arises from?
Medium
  1. 4Example of redifferentiation?
  2. 5Heterophylly example?
  3. 6Environmental heterophylly in?
Challenging
  1. 7Development includes?
  2. 8Define plasticity.
Show answers (try them yourself first)
  1. 1Permanent change for specialisation.
  2. 2Cortex cells by dedifferentiation.
  3. 3Parenchyma.
  4. 4Secondary xylem.
  5. 5Cotton / coriander.
  6. 6Ranunculus.
  7. 7Growth, morphogenesis, maturation, senescence.
  8. 8Changing form with conditions.

Auxin and gibberellin

From daily life

A plant near a window bends to the light — thanks to auxin.

Simple definition

Plant hormones = organic substances made by plants; act away from the site of production, in very small amounts (Thimann–Pincus 1948).

Auxin and GAAuxin and gibberellinlightbends: auxin on shaded sideAvena coleoptile (Went 1928)IAAIBA, NAA, 2,4-Dtips → basipetalAuxin: cell elongation; apical dominance; callus; roots; prevents fruit dropDarwin 1886; Boysen-Jensen 1910; Paal 1919; Went 19282,4-D = weedicide; Agent Orange (2,4-D + 2,4,5-T)Gibberellin: Kurosawa 1926 (bakane disease, Gibberella); GA₃GA: stem elongation, dwarf → tall, bolting, parthenocarpy, grape bunchGA: breaks seed dormancy; replaces vernalizationBioassay: Avena curvature (auxin); α-amylase (GA)

In the figure : Coleoptile and auxin; uses of gibberellin.

Rule 1 : Auxin — Discovery: Darwin 1886 (bending to light), Boysen-Jensen 1910 (gelatin plate), Paal 1919, Went 1928 (Avena coleoptile + agar block). Natural auxin = IAA (from tryptophan); synthetic: IBA, NAA, 2,4-D. Made in growing tips; basipetal transport. Functions: cell elongation; apical dominance; callus in tissue culture; rooting; prevents fruit drop; flowering in litchi/pineapple; breaks seed dormancy. 2,4-D is a weedicide; Agent Orange = 2,4-D + 2,4,5-T.

  • Easy : IAA = natural auxin.
  • Medium : Went = 1928.
  • Exam-type (CET) : Apical dominance = auxin.

Rule 2 : Gibberellin — Discovery: Kurosawa 1926 — fungus Gibberella fujikuroi caused bakane (over-tall) disease of rice; Yabuta–Sumiki 1938 crystallised it. Commonest GA₃; 150+ kinds; made in young leaves, seeds, roots, tips; non-polar transport. Functions: internode elongation, dwarf → tall (maize), bolting (beet, cabbage), parthenocarpy (tomato, apple), larger grape bunches, germination of barley/wheat (α-amylase), breaks dormancy, replaces vernalization; inhibits root growth.

  • Easy : GA₃ = gibberellic acid.
  • Medium : Bakane = rice.
  • Exam-type (CET) : Bolting = beet, cabbage.
Remember

Auxin = cell stretch & light bending; GA = gets taller.

Common mistake and CET trap

‘Auxin moves acropetally’ is wrong (basipetal). Trap: ‘GA promotes root growth’ is wrong.

Shortcut

Memory clue : "IAA = I am auxin; GA = gets taller".

Spot the difference

HormoneMain role
AuxinCell elongation, apical dominance
GAInternode length, bolting

Practice questions

Easy
  1. 1First plant hormone discovered?
  2. 2Went used which plant?
  3. 3Natural auxin?
Medium
  1. 4Apical dominance is due to?
  2. 5Use of 2,4-D?
  3. 6Bakane disease?
Challenging
  1. 7One use of GA?
  2. 8Parthenocarpy induced by?
Show answers (try them yourself first)
  1. 1Auxin.
  2. 2Avena coleoptile.
  3. 3IAA.
  4. 4Auxin.
  5. 5Weedicide.
  6. 6Gibberella → over-growth of rice.
  7. 7Dwarf → tall / grape bunches.
  8. 8GA / auxin.

Cytokinin, ethylene and ABA

From daily life

Raw mangoes ripen near a ripe banana — due to ethylene gas.

Simple definition

Cytokinin = cell-division hormone. Ethylene = the only gaseous hormone. ABA = growth-inhibiting stress hormone.

Cytokinin, ethylene, ABACytokinin, ethylene, ABACytokininEthyleneABAcell divisionthe only gasstress hormoneCytokinin: Skoog–Miller 1954 kinetin; zeatin = natural (maize)High cytokinin : auxin → shoots; low → rootsCytokinin: delays senescence; reverses apical dominanceEthylene: ripens fruit (banana, mango); ethephon; abscissionEthylene: epinasty; flowering in pineapple; degreeningABA: dormancy, abscission, senescence; closes stomataABA: Addicott 1961–65 (abscisin); Wareing 1963 (dormin)Promoters: auxin, GA, CK; inhibitors: ethylene, ABA

In the figure : Three hormones and their roles.

Rule 1 : Cytokinin — Skoog–Miller 1954 — tobacco callus grew with coconut milk and old DNA; kinetin (6-furfuryl amino purine). First natural = zeatin (from young maize, Letham). Functions: cell division and enlargement; high cytokinin : auxin = shoots, low = roots; growth of lateral buds (reverses apical dominance); delays senescence and abscission; seed germination; RNA synthesis; interfascicular cambium.

  • Easy : Kinetin = 1954.
  • Medium : Zeatin = natural.
  • Exam-type (CET) : High CK = shoots.

Rule 2 : Ethylene and ABA — Ethylene: Denny 1924 (ripening), Gane 1934 (plants make it), Crocker 1930. Ethephon (2-chloroethyl phosphonic acid) releases ethylene in water. Functions: ripens fruit (banana, apple, mango), abscission layer, lateral roots, breaks dormancy, epinasty, flowering in pineapple, degreening of banana/citrus. ABA: Addicott 1961–65 (abscisin; cotton boll fall), Wareing 1963 (dormin, Acer buds); 15-carbon sesquiterpenoid. Functions: dormancy, abscission, senescence, inhibits cell division, K⁺ efflux from guard cells ⇒ stomata close (antitranspirant); inhibits flowering in long-day plants.

  • Easy : Ethylene = gas; ripens fruit.
  • Medium : ABA = antitranspirant.
  • Exam-type (CET) : Ethephon = source of ethylene.
Remember

CK = cell division; ethylene = ripening; ABA = brake.

Common mistake and CET trap

‘Ethylene is a liquid hormone’ is wrong (gas). Trap: ‘ABA opens stomata’ is wrong.

Shortcut

Memory clue : "Promoters = A-G-C; inhibitors = E-A".

Spot the difference

HormoneEffect
CytokininCell division; delays senescence
EthyleneRipening; abscission
ABADormancy; stomata close

Practice questions

Easy
  1. 1Who discovered kinetin?
  2. 2First natural cytokinin?
  3. 3Low CK : auxin gives?
Medium
  1. 4Only gaseous hormone?
  2. 5What is ethephon?
  3. 6Degreening is caused by?
Challenging
  1. 7Another name of ABA?
  2. 8Which hormone is antitranspirant?
Show answers (try them yourself first)
  1. 1Skoog and Miller (1954).
  2. 2Zeatin.
  3. 3Roots.
  4. 4Ethylene.
  5. 5A source of ethylene.
  6. 6Ethylene.
  7. 7Dormin / abscisin.
  8. 8ABA.

Photoperiodism and vernalization

From daily life

Some flowers open only in winter and some only in summer — due to length of daylight.

Simple definition

Photoperiodism = effect of relative day/night length on flowering. Vernalization = acceleration of flowering ability by chilling.

PhotoperiodismPhotoperiodism and vernalizationSDPLDPDNPlong nightshort nightindependentPrPfr660730 nmPfr by day; Pr by nightGarner–Allard 1920: soybean, Maryland Mammoth tobaccoSDP: Dahlia, Aster, Chrysanthemum, Xanthium; LDP: pea, radish, wheatDNP: tomato, cotton, sunflower, maizeLeaf = receptor; florigen via phloem; Hendricks–Borthwick 1952Vernalization: 1–6 °C for 1–1½ months; Lysenko 1928Site = shoot apical meristem; vernalin; transferred by graftingWinter wheat needs chilling; devernalization = reversal by heat

In the figure : SDP, LDP, DNP and phytochrome.

Live figure

Photoperiodism and vernalization

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Rule 1 : Photoperiodism — Garner–Allard 1920 (soybean; Maryland Mammoth tobacco) — not temperature, nutrition or moisture but light duration decides flowering. SDP (long night; day shorter than critical photoperiod): Dahlia, Aster, Chrysanthemum, Xanthium; a flash in the night stops flowering. LDP (short night): pea, radish, beet, cabbage, spinach, wheat. DNP: tomato, cotton, sunflower, maize. Leaf = receptor (Knoff 1934); florigen moves through phloem. Phytochrome: Pr (660 nm red) ⇄ Pfr (730 nm far-red); Hendricks–Borthwick 1952; Pfr accumulates by day (inhibits SDP, promotes LDP); at night Pfr → Pr (promotes SDP).

  • Easy : SDP = long night.
  • Medium : Phytochrome = Pr ⇄ Pfr.
  • Exam-type (CET) : Leaf = receptor.

Rule 2 : Vernalization — Klippart noticed winter vs spring wheat; Lysenko 1928 coined the term. Method: seeds/seedlings chilled at 1–6 °C for one to one-and-a-half months. Winter wheat without chilling flowers only the next year. Site = shoot apical meristem; chemical stimulus vernalin (Melchers) — transferred by grafting (Melcher 1939). Reversal by heat = devernalization. Advantages: earlier flowering, shorter juvenile phase, crops in regions without cold.

  • Easy : 1–6 °C.
  • Medium : Devernalization = heat.
  • Exam-type (CET) : Site = apical meristem.
Remember

SDP = long dark; LDP = short dark.

Common mistake and CET trap

‘SDP needs long days’ is wrong (long nights). Trap: ‘Pfr accumulates at night’ is wrong (by day).

Shortcut

Memory clue : "Red makes Pfr; far-red makes Pr".

Spot the difference

TypeNightExample
SDPLongChrysanthemum
LDPShortPea
DNPIndependentTomato

Practice questions

Easy
  1. 1Who coined photoperiodism?
  2. 2SDP example?
  3. 3LDP example?
Medium
  1. 4Receptor organ?
  2. 5Florigen travels through?
  3. 6Vernalization temperature?
Challenging
  1. 7Who coined vernalization?
  2. 8Devernalization is?
Show answers (try them yourself first)
  1. 1Garner and Allard.
  2. 2Dahlia / Chrysanthemum.
  3. 3Pea / wheat.
  4. 4Leaf.
  5. 5Phloem.
  6. 61–6 °C.
  7. 7Lysenko (1928).
  8. 8Reversal by high temperature.

Mineral nutrition

From daily life

Water alone doesn't feed a field; fertiliser adds the minerals.

Simple definition

An essential element = one without which the plant cannot complete its life cycle. Chlorosis = loss of chlorophyll; yellow leaves.

Mineral nutritionMineral nutrition and deficiency symptomsMacro: N P K Ca Mg S FeMicro: Zn Cu Mn B Mo ClOld leaves first: N, Mg, K (mobile)Young leaves first: S, Ca (immobile)Arnon–Stout 1939: criteria of essentiality; Liebig = law of minimumStunting, chlorosis (yellowing), necrosis, mottling, abscissionN: proteins, chlorophyll → chlorosis; K: stomata, turgorCa: middle lamella (Ca pectate); B: brown heart; Mo: N metabolismMg: chlorophyll; Zn: auxin synthesis; Cu: die-backPassive: diffusion, Donnan; active: ATP, carrier (Hoagland–Davis 1923)Minerals absorbed independent of water; xylem → phloem redistributionToxic = reduces dry weight by 10%; Mn blocks Fe, Mg

In the figure : Macro/micro elements and deficiency signs.

Rule 1 : Classification and deficiency symptoms — About 36–40 elements are used; as ions, through roots. C, H, O come from air and water; N from soil (mineral and non-mineral). Macro (large amounts: structure/nutrition): C, H, O, N, P, K, Ca, Mg, S, Fe; micro (traces: catalytic, co-factors): Zn, Cu, Mn, B, Mo, Cl. Criteria of essentiality (Arnon–Stout 1939): indispensable for normal growth and reproduction; specific role; cannot be replaced by another. Liebig: law of minimum. Symptoms: stunting, chlorosis, necrosis, mottling, abscission. Mobile (N, Mg, K): old leaves first; immobile (S, Ca): young leaves first.

  • Easy : Mobile = old leaves first.
  • Medium : Immobile = S, Ca.
  • Exam-type (CET) : Liebig = law of minimum.

Rule 2 : Roles of some elements; absorption — N: proteins, nucleic acids, chlorophyll → deficiency: stunting, chlorosis. P: membranes, ATP, nucleic acids. K: stomata, turgor, enzymes. Ca: middle lamella (Ca pectate). Mg: chlorophyll. S: proteins, vitamins. Zn: auxin synthesis; B: brown heart; Mo: N metabolism; Cu: die-back; Cl: O₂ evolution. Absorption (independent of water): passive (diffusion, ion-exchange, mass flow, Donnan equilibrium) and active (against gradient, ATP; carrier hypothesis — Hoagland–Davis 1923). Without O₂ active uptake drops; transport xylem → leaves → phloem. A concentration cutting dry weight by 10% = toxic.

  • Easy : Mg = chlorophyll.
  • Medium : Active = ATP.
  • Exam-type (CET) : Boron = brown heart.
Remember

N, Mg, K show in old leaves; S, Ca in young leaves.

Common mistake and CET trap

‘Ca moves from old to young leaves’ is wrong. Trap: ‘minerals are absorbed only with water’ is wrong.

Shortcut

Memory clue : "C-HOPKNS CaFe Mg = macro".

Spot the difference

ElementRoleDeficiency
NProteinsChlorosis
MgChlorophyllChlorosis
BCa uptakeBrown heart

Practice questions

Easy
  1. 1Macro example?
  2. 2Micro example?
  3. 3Chlorosis means?
Medium
  1. 4Liebig's law?
  2. 5A mobile element?
  3. 6Where does Ca function?
Challenging
  1. 7Donnan equilibrium is?
  2. 8Active absorption needs?
Show answers (try them yourself first)
  1. 1N / P / K.
  2. 2Zn / Cu / Mn.
  3. 3Yellowing of leaves.
  4. 4Law of minimum.
  5. 5N / K / Mg.
  6. 6Middle lamella.
  7. 7Passive absorption.
  8. 8ATP / energy.

Nitrogen cycle

From daily life

Soil after gram or tur becomes fertile for the next crop — thanks to root nodules.

Simple definition

Nitrogen fixation = conversion of atmospheric N₂ into salts that plants can use.

Nitrogen cycleNitrogen cycleN₂NH₃/NH₄⁺NO₂⁻NO₃⁻FixationNitrificationDenitrification → N₂Physical: lightning + O₂ → NO → NO₂ → HNO₃ (rain to soil)Industrial: Haber–Bosch — 450 °C, 200 atm; N₂ + 3H₂ → 2NH₃Biological ~70%: Rhizobium (legumes), Azotobacter, cyanobacteria (heterocyst)Nitrogenase: N₂ + 8H⁺ + 8e⁻ + 16 ATP → 2NH₃ + H₂Ammonification: dead tissue → NH₃ (fungi, actinomycetes)Nitrification: Nitrosomonas (NH₃ → NO₂⁻), Nitrobacter (→ NO₃⁻)Denitrification: Pseudomonas → N₂ back to airAssimilation: NO₃⁻ → NH₃ → amino acids → proteins

In the figure : Stages of the nitrogen cycle.

Live figure

Nitrogen cycle

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Rule 1 : Nitrogen fixation — N₂ has an N≡N triple bond — inert. Physical: lightning, N₂ + O₂ → 2NO → 2NO₂ → rain gives HNO₂ + HNO₃ → with Ca/K salts in soil forms nitrates. Industrial: Haber–Bosch — N₂ + 3H₂ → 2NH₃, 450 °C, 200 atm; then urea. Biological (~70%): diazotrophs — Rhizobium (nodules on legumes; symbiotic), Azotobacter (free-living), cyanobacteria (heterocysts). Nitrogenase: N₂ + 8H⁺ + 8e⁻ + 16 ATP → 2NH₃ + H₂ — energy-costly.

  • Easy : Haber–Bosch = 450 °C, 200 atm.
  • Medium : Rhizobium = legumes.
  • Exam-type (CET) : Biological = ~70%.

Rule 2 : The other steps of the cycle — Ammonification: fungi, actinomycetes and bacteria decompose dead plants/animals: protein → amino acids → NH₃. Nitrification: Nitrosomonas NH₃ → NO₂⁻; Nitrobacter NO₂⁻ → NO₃⁻. Assimilation: roots take NO₃⁻ → NH₃ → amino acids → proteins; animals get it by eating plants. Denitrification: Pseudomonas, Thiobacillus — NO₃⁻ → N₂, back to atmosphere. Soil nitrogen is a limiting nutrient in agriculture.

  • Easy : Nitrosomonas: NH₃ → NO₂⁻.
  • Medium : Nitrobacter: NO₂⁻ → NO₃⁻.
  • Exam-type (CET) : Denitrification → N₂.
Remember

Nitrosomonas makes nitrite; Nitrobacter takes it to nitrate.

Common mistake and CET trap

‘Rhizobium is free-living’ is wrong (symbiotic). Trap: ‘denitrification increases nitrate’ is wrong.

Shortcut

Memory clue : "A-N-A-D steps".

Spot the difference

ProcessOrganismResult
FixationRhizobiumN₂ → NH₃
NitrificationNitrosomonas / NitrobacterNO₃⁻
DenitrificationPseudomonasN₂

Practice questions

Easy
  1. 1Why is N₂ inert?
  2. 2Haber–Bosch conditions?
  3. 3Rhizobium lives in?
Medium
  1. 4Heterocysts occur in?
  2. 5Ammonification is?
  3. 6Function of Nitrosomonas?
Challenging
  1. 7Denitrification gives?
  2. 8Biological fixation %?
Show answers (try them yourself first)
  1. 1Triple bond.
  2. 2450 °C, 200 atm.
  3. 3Root nodules of legumes.
  4. 4Cyanobacteria.
  5. 5Dead matter → NH₃.
  6. 6NH₃ → NO₂⁻.
  7. 7N₂.
  8. 8~70%.

Quick revision of the whole lesson

ConceptKey fact
GrowthLag → log → stationary; AGR/RGR
DifferentiationDe-diff = divides again
Auxin / GAIAA (Went 1928); GA₃ (Kurosawa 1926)
CK / C₂H₄ / ABAKinetin 1954; ripening; stomata close
PhotoperiodSDP long night; vernalization 1–6 °C
MineralsMobile N, Mg, K; immobile S, Ca
N cycleFixation → nitrification → denitrification

🎯 Most important points for the exam

  • Meristems and phases.
  • Dedifferentiation, plasticity.
  • Auxin and gibberellin.
  • Cytokinin, ethylene, ABA.
  • SDP/LDP, phytochrome, vernalization.
  • Macro/micro, deficiency signs.
  • Nitrogen cycle.
Study mantra

Understand the concept → draw the figure → memorise the key points → solve questions yourself.