Schooling · Class 11 · Biology · Plant Growth and Development · Chapter on a page
CBSE Class 11 · Biology · NCERT Biology
Plant Growth and Development: chapter on a page
A cut of Shishya's notes for this chapter: the first paragraph of the introduction and the key ideas, formulas and facts, common mistakes and quick revision lists, word for word. Nothing is added or reworded; the worked examples are left out (they are on the chapter page).
About the notes: Written by Shishya's AI on 27 Sept 2026 from the chapter's title and class level, in Shishya's own words — not a copy or summary of the textbook. Read the official chapter for the book's own text, activities and exercises.
This note's current text has no applied fact-check on record.
Mind map
Drawn from the same notes by a fixed rule (no AI): each label is the item's own words — its bold term, its label before a colon, a short formula as written, or its first words.
The mind map as a list
- Key ideas
- Growth is irreversible permanent…
- Growth can be measured
- Growth occurs in three phases
- The growth rate
- Plant hormones (phytohormones)
- Photoperiodism
- Vernalisation
- Formulas and facts
- Arithmetic growth
- Exponential (geometric) growth
- Relative growth rate (RGR)
- Auxins
- Gibberellins
- Cytokinins
- Abscisic acid (ABA)
- Worked examples
- Calculating arithmetic growth
- Predicting flowering based on…
- Role of hormones in fruit ripening
- Watch out for
- Thinking growth occurs throughout…
- Confusing growth with development
- Believing all hormones only promote…
- Assuming short-day plants need short…
- Mixing up apical dominance and…
What this chapter is about
This chapter introduces the unique characteristics of plant growth, which differs fundamentally from animal growth. Plants grow throughout their life (indeterminate growth), and growth occurs only in specific regions containing meristematic tissue. A Class 11 student learns how growth is measured, what phases growth passes through, and the factors that influence it.
Key ideas
- Growth is irreversible permanent increase in size accompanied by increase in dry mass, cell number, and complexity; it occurs in meristematic regions (root tip, shoot tip, cambium).
- Growth can be measured by increase in fresh weight, dry weight, length, area, volume, or cell number; the simplest method is measuring increase in length over time.
- Growth occurs in three phases: the cell division phase (meristematic), the cell enlargement phase (elongation), and the cell maturation phase (differentiation).
- The growth rate of a plant organ can follow arithmetic growth (constant addition, e.g., root elongating at fixed length per day) or geometric growth (exponential increase when all daughter cells continue dividing).
- Plant hormones (phytohormones) are organic molecules produced in minute quantities that regulate growth and development; the five major groups are auxins, gibberellins, cytokinins, abscisic acid, and ethylene.
- Photoperiodism is the response of plants to the relative lengths of day and night, which controls flowering in short-day, long-day, and day-neutral plants.
- Vernalisation is the promotion of flowering by exposure to low temperatures for a certain period, important in winter crops like wheat.
- Seed dormancy prevents germination even under favourable conditions; it is broken by factors like light, temperature, or hormone balance.
Formulas and facts to remember
- Arithmetic growth: L_t = L_0 + r × t, where L_t is final length, L_0 is initial length, r is elongation rate per unit time, and t is time. Growth adds a constant amount per unit time.
- Exponential (geometric) growth: W_t = W_0 × e^(r × t), where W_t is final size (weight or number), W_0 is initial size, r is relative growth rate, and t is time. Growth doubles repeatedly.
- Relative growth rate (RGR) = (W_2 − W_1) / (W_1 × (t_2 − t_1)), measuring growth per unit of existing material per unit time.
- Auxins (e.g., indole-3-acetic acid, IAA) promote cell elongation, apical dominance, root initiation, and are used in rooting of cuttings and as herbicides at high concentrations.
- Gibberellins (e.g., GA_3) promote stem elongation, bolting in rosette plants, breaking of seed dormancy, and delay senescence.
- Cytokinins (e.g., zeatin, kinetin) promote cell division, delay leaf senescence, and help overcome apical dominance by promoting lateral bud growth.
- Abscisic acid (ABA) inhibits growth, promotes stomatal closure during water stress, and induces seed dormancy; often called the stress hormone.
- Ethylene (C₂H₄), a gaseous hormone, promotes fruit ripening, leaf abscission, and senescence; used commercially to ripen fruits like bananas.
Common mistakes
- Thinking growth occurs throughout the plant body → growth is localised to meristematic regions; mature cells do not divide.
- Confusing growth with development → growth is quantitative increase in size; development includes differentiation and morphogenesis.
- Believing all hormones only promote growth → ABA inhibits growth and ethylene can promote senescence and abscission.
- Assuming short-day plants need short days → they actually require long, uninterrupted nights (darkness is the critical factor).
- Mixing up apical dominance and lateral growth → auxin from the apical bud suppresses lateral buds; removing the apex or adding cytokinin promotes lateral branching.
Quick revision
- Plant growth is irreversible, localised (meristems), and measurable by length, weight, or cell number.
- Three phases of growth: division → elongation → differentiation.
- Five major hormones: auxins, gibberellins, cytokinins, ABA (inhibitor), ethylene (gaseous).
- Photoperiodism = flowering response to day-night ratio; vernalisation = flowering response to cold treatment.
- Ethylene ripens fruits; ABA closes stomata and induces dormancy; cytokinins delay senescence.
- Relative growth rate compares growth efficiency across different plants or organs.