Plant Growth and Development
Class 11 · Biology
5 ideas in Class 11 Biology, explained in plain words, with games and quizzes to practise.
Growth Basics
Part of: Growth Basics and Rates
Growth permanently enlarges organs at energy cost; meristems add cells lifelong while wood swelling merely reverses. Root and stem tips lengthen, cambia thicken; maize counts cells hourly while melons balloon them; zones divide, elongate and finish under water, air, food, warmth and cues.
Why it matters. Permanent versus reversible splits growth from swelling. Zone order maps root tips.
Key words
- Growth
- : A permanent and irreversible increase in the size or dry weight of an organ.
- Meristem
- : A region of dividing cells that adds new cells for lifelong plant growth.
- Apical meristem
- : Dividing cells at root and stem tips that cause lengthwise growth.
- Lateral meristem
- : Dividing cells on the sides, like cambia, that cause thickness growth.
- Open growth
- : The plant habit of adding new cells lifelong through meristem activity.
Try it in two minutes
- Define growth precisely.
- Name three meristems.
- Order three root zones.
Try at home. Mark seedling roots daily.
Growth Rates
Part of: Growth Basics and Rates
Single-dividing daughters draw straight lines while doubling daughters trace S-curves through lag, log and stationary phases; totals clock absolute rates while per-unit gains clock relative ones; W0 seeds exponential W1 through efficiency r.
Why it matters. Curve shapes diagnose growth modes. Relative rates fairly compare unequals.
Formulas
- Lt = L0 + rt (arithmetic growth of length)
- W1 = W0 e^(rt) (exponential growth of size)
- Relative rate = absolute rate / initial size
Key words
- Absolute growth rate
- : The total growth of a system per unit time.
- Relative growth rate
- : Growth per unit time stated per unit of initial size.
- Arithmetic growth
- : Growth where only one daughter cell keeps dividing, giving a straight-line plot.
- Geometric growth
- : Growth where both daughter cells divide, giving an S-shaped curve.
- Lag phase
- : The early slow stage of geometric growth before rapid increase.
Try it in two minutes
- Plot steady root growth.
- Trace one S-curve.
- Compare two leaves fairly.
Try at home. Plot seedling height for a week.
Differentiation and Plasticity
Part of: Differentiation and Development
Meristem daughters mature into specialists like empty strong tracheary tubes; living specialists can redivide into cambia then remature; positions steer fates while age and habitat reshape leaves; growth plus differentiation sums to development.
Why it matters. Reversible fates enable grafting and culture. Plasticity explains varied leaves.
Key words
- Differentiation
- : The maturing of meristem cells into specialised permanent cells.
- Dedifferentiation
- : The return of mature living cells to a dividing state, as in cork cambia.
- Redifferentiation
- : The maturing of dedifferentiated cells into new specialised forms.
- Plasticity
- : The ability of a plant to follow different developmental paths with age or habitat.
- Development
- : The sum of growth and differentiation that shapes the whole life of a plant.
Try it in two minutes
- Order differ, dediffer, rediffer.
- Spot two heterophylly cases.
- Add growth to differentiation.
Try at home. Compare juvenile with adult leaves.
PGR Discovery and Groups
Part of: Plant Growth Regulators
Tiny diverse molecules split into promoters auxin, gibberellin and cytokinin versus stress-dormancy ABA, with ethylene straddling; accidents revealed coleoptile tips, foolish seedlings, herring kinetin, triple inhibitors and orange-gas ripening.
Why it matters. Function groups predict field uses. Accident stories anchor each group.
Key words
- Phytohormone
- : A plant-made chemical that controls growth and responses in tiny amounts.
- Auxin
- : The growth promoter first found from coleoptile tips that bends stems toward light.
- Gibberellin
- : The promoter found from foolish seedlings that stretches stems and breaks dormancy.
- Cytokinin
- : A promoter that drives cell division, branching and delayed leaf ageing.
- Abscisic acid
- : The stress hormone that closes stomata and enforces seed dormancy.
Try it in two minutes
- Sort five groups by role.
- Match each find with its group.
- Place ethylene between groups.
Try at home. Ripen bananas with oranges nearby.
Hormone Effects
Part of: Plant Growth Regulators
Auxins root cuttings, flower pineapples, guard young fruits yet shed old ones, crown apices and clear dicot weeds; GAs stretch grapes and sugarcane, bolt rosettes and malt grain; cytokinins branch and freshen; ethylene hooks, ripens, drops and ethephon-tunes crops; ABA shuts pores and sleeps seeds against GAs.
Why it matters. Effect lists guide farming tricks. Antagonist pairs explain dormancy control.
Key words
- Apical dominance
- : The suppression of side buds by auxin flowing down from the growing tip.
- Bolting
- : Rapid stem elongation before flowering, promoted by gibberellins in rosette plants.
- Senescence
- : The ageing of leaves and organs, delayed by cytokinins and hastened by ethylene.
- Abscission
- : The shedding of leaves, flowers or fruits, influenced by auxin and ethylene.
- Triple response
- : The ethylene effect in seedlings of short thick stems with a tight apical hook.
Try it in two minutes
- List three auxin farm uses.
- Stretch one crop with GA.
- Wake seeds against ABA.
Try at home. Root a cutting with honey versus plain water.
What your child will practise
- Differentiation and Plasticity: Desert Quick Fire (Quick Fire)
- Growth Basics: Space Puzzle (Clue Puzzle)
- Growth Rates: Ocean Quick Fire (Quick Fire)
- Hormone Effects: Ocean Quest (Flip and Match)
- PGR Discovery and Groups: Candy Puzzle (Clue Puzzle)
- Quiz: Differentiation and Plasticity (8 questions)
- Quiz: Growth Basics (8 questions)
- Quiz: Growth Rates (8 questions)
- Quiz: Hormone Effects (8 questions)