Plant Growth and Development NEET Notes 2027: Key Points and PDF

Plant Growth and Development is Chapter 13 of NCERT Class 11 Biology and part of Unit 4, Plant Physiology, of the NEET UG syllabus. These notes cover growth, its phases and rates, conditions for growth, differentiation, dedifferentiation and redifferentiation, development and plasticity, and the five plant growth regulators, with a free notes PDF.

Plant Growth and Development NEET Notes

Section-wise key points from NCERT Chapter 13, comparison tables, high-yield facts and common mistakes for NEET 2027 revision.

Plant Growth and Development at a Glance

The topic list follows the NEET UG 2026 syllabus released by the National Medical Commission (NMC) on 22 December 2025, which stays the reference until the 2027 syllabus is out. The full list is on the NEET syllabus page.

The rationalised NCERT chapter has no sections on photoperiodism and vernalisation, and the NEET UG 2026 syllabus does not list them, so they are left out here.

What is growth and why is plant growth indeterminate?

Growth is an irreversible permanent increase in size of an organ, its parts or even a single cell, usually accompanied by anabolic and catabolic processes that use energy.

• Development starts from the zygote. The first step of plant growth is seed germination, which happens only when conditions are favourable; otherwise the seed stays in a period of suspended growth or rest.
• Plants keep the capacity for unlimited growth throughout life because of meristems, whose cells divide and self-perpetuate. Adding new cells this way is the open form of growth.
• Root and shoot apical meristems cause primary growth, the elongation of the plant along its axis.
• In dicots and gymnosperms, the lateral meristems (vascular cambium and cork-cambium) appear later and increase girth: secondary growth.

Growth Is Measurable

• Growth is mainly an increase in protoplasm, measured indirectly by fresh weight, dry weight, length, area, volume or cell number.
• One maize root apical meristem can give rise to more than 17,500 new cells per hour (increase in cell number).
• Cells in a watermelon may increase in size by up to 3,50,000 times (increase in cell size).
• Pollen tube growth is measured by length; dorsiventral leaf growth by surface area.

What are the phases of growth?

Growth is divided into three phases, seen from the tip of a root backwards: meristematic, elongation and maturation.

Growth Rates: Arithmetic and Geometric Growth

Growth rate is the increased growth per unit time, and it can be arithmetic or geometric.

• In geometric growth, initial growth is slow (lag phase), then exponential (log phase), and slows with limited nutrients (stationary phase).
• In W1 = W0 e^rt, r is the relative growth rate, a measure of the plant’s ability to produce new material, called the efficiency index. Final size W1 depends on initial size W0.
• Absolute growth rate is total growth per unit time; relative growth rate is growth per unit time on a common basis, such as per unit initial size. Of two leaves gaining the same area, the smaller one has the higher relative growth rate.

What conditions does a plant need to grow?

Water, oxygen and nutrients are essential, along with an optimum temperature range.

• Water: cells grow by enlargement, which needs water; turgidity helps extension growth, and water is the medium for enzyme activity.
• Oxygen: helps release metabolic energy for growth.
• Nutrients (macro and micro essential elements): needed to make protoplasm and act as a source of energy.
• Temperature: every plant has an optimum range; deviation can harm survival.
• Environmental signals such as light and gravity also affect certain phases of growth.

Differentiation, Dedifferentiation and Redifferentiation

Cells from apical meristems and cambium mature to perform specific functions; some mature cells can later divide again.

• Differentiation in plants is open: cells from the same meristem have different structures at maturity, depending on location.
• Cells positioned away from the root apical meristem differentiate as root-cap cells, while those pushed to the periphery mature as epidermis.

Development and Plasticity

Development includes all changes an organism goes through from seed germination to senescence; it is the sum of growth and differentiation.

• Sequence in a plant cell (NCERT Figure 13.8): a meristematic cell divides; through plasmatic growth, expansion (elongation), differentiation and maturation it becomes a mature cell, which ends in senescence and death.
• Plasticity is the ability to follow different pathways in response to environment or phase of life and form different structures.
• Heterophylly due to phase of life: cotton, coriander and larkspur, where juvenile leaves differ in shape from mature leaves.
• Heterophylly due to environment: buttercup, where leaves formed in air differ from those formed in water.
• Development is controlled by intrinsic factors (intracellular genetic factors and intercellular chemicals such as PGRs) and extrinsic factors (light, temperature, water, oxygen, nutrition).

Plant Growth Regulators: Nature and Discovery

Plant growth regulators (PGRs), also called plant growth substances, plant hormones or phytohormones, are small, simple molecules of diverse chemical composition.

The discovery of each of the five major groups of PGRs was accidental.

Physiological Effects of the Five Plant Growth Regulators

Each PGR has many effects, and different PGRs can show similar effects.

Auxins

• First isolated from human urine. Natural auxins: IAA and indole butyric acid (IBA); synthetic: NAA (naphthalene acetic acid) and 2, 4-D.
• Produced at growing apices of stems and roots and migrate to regions of action.
• Initiate rooting in stem cuttings; promote flowering, e.g. in pineapples.
• Prevent early fruit and leaf drop but promote abscission of older, mature leaves and fruits.
• Apical dominance: the apical bud inhibits lateral buds; decapitation (removing the shoot tip) lets lateral buds grow, used in tea plantations and hedge-making.
• Induce parthenocarpy, e.g. in tomatoes. 2, 4-D kills dicot weeds but does not affect mature monocots, so it is used for weed-free lawns.
• Control xylem differentiation and help in cell division.

Gibberellins

• More than 100 gibberellins (GA1, GA2, GA3 and so on) are known from fungi and higher plants; all are acidic. GA3 was one of the first discovered and is the most studied.
• Increase the length of grape stalks; make apples elongate and improve their shape.
• Delay senescence, so fruits stay on the tree longer and the market period is extended.
• GA3 speeds up malting in the brewing industry.
• Spraying sugarcane increases stem length and yield by as much as 20 tonnes per acre.
• Spraying juvenile conifers hastens maturity and early seed production.
• Promote bolting (internode elongation just before flowering) in beet, cabbage and other rosette plants.

Cytokinins

• Discovered as kinetin, a modified adenine (purine), from autoclaved herring sperm DNA. Kinetin does not occur naturally in plants.
• Zeatin, a natural cytokinin, was isolated from corn kernels and coconut milk.
• Made where rapid cell division occurs: root apices, developing shoot buds, young fruits.
• Help form new leaves, chloroplasts in leaves, lateral shoot growth and adventitious shoots.
• Help overcome apical dominance and promote nutrient mobilisation, which delays leaf senescence.

Ethylene

• A simple gaseous PGR made in large amounts by tissues undergoing senescence and by ripening fruits.
• Causes horizontal growth of seedlings, swelling of the axis and apical hook formation in dicot seedlings.
• Promotes senescence and abscission, especially of leaves and flowers, and is highly effective in fruit ripening. The rise in respiration rate during ripening is the respiratory climacteric.
• Breaks seed and bud dormancy, starts germination in peanut seeds and sprouting of potato tubers.
• Promotes rapid internode or petiole elongation in deep water rice, keeping upper parts above water; promotes root growth and root hair formation.
• Initiates flowering and synchronises fruit-set in pineapples; induces flowering in mango.
• Ethephon is the most widely used source of ethylene: it hastens ripening in tomatoes and apples, accelerates abscission in flowers and fruits (thinning of cotton, cherry, walnut) and promotes female flowers in cucumbers.

Abscisic Acid (ABA)

• A general plant growth inhibitor and inhibitor of plant metabolism; inhibits seed germination.
• Stimulates closure of stomata and increases tolerance to stresses, so it is called the stress hormone.
• Important in seed development, maturation and dormancy; dormancy helps seeds withstand desiccation.
• In most situations ABA acts as an antagonist to GAs.

PGR roles can be complementary or antagonistic, individualistic or synergistic. Events such as seed and bud dormancy, abscission, senescence and apical dominance involve more than one PGR.

Most-asked Facts for NEET: Plant Growth and Development

Revise these one-line facts from the NCERT chapter just before the exam.

• Growth is irreversible; plant growth is open (indeterminate) because of meristems.
• A maize root apical meristem gives more than 17,500 new cells per hour; watermelon cells grow up to 3,50,000 times in size.
• Phases of growth: meristematic, elongation, maturation.
• Arithmetic growth: Lt = L0 + rt (linear); geometric growth: W1 = W0 e^rt (sigmoid).
• Relative growth rate r is also called the efficiency index.
• Dedifferentiation example: interfascicular cambium and cork cambium from parenchyma.
• Heterophylly: cotton, coriander, larkspur (phase of life); buttercup (environment).
• Auxin was first isolated from human urine; F.W. Went isolated it from oat coleoptile tips.
• Bakanae disease of rice: Gibberella fujikuroi; E. Kurosawa, 1926.
• Kinetin came from autoclaved herring sperm DNA; zeatin from corn kernels and coconut milk.
• ABA was found as inhibitor-B, abscission II and dormin.
• H.H. Cousins (1910): volatile from ripened oranges hastened banana ripening (ethylene).
• 2, 4-D kills dicot weeds, not mature monocots.
• Gibberellins: bolting in beet and cabbage, malting, longer sugarcane stems.
• Cytokinins delay leaf senescence and overcome apical dominance.
• Ethephon releases ethylene; ethylene promotes female flowers in cucumbers.
• ABA is the stress hormone and closes stomata; it is antagonistic to GAs.

Common Mistakes to Avoid

Watch for these mix-ups when you answer questions on this chapter.

• Saying kinetin is a natural plant hormone. It does not occur naturally in plants; zeatin is a natural cytokinin.
• Writing that 2, 4-D kills monocot weeds. It kills dicot weeds and does not affect mature monocots.
• Mixing up arithmetic and geometric growth: in arithmetic growth only one daughter cell keeps dividing.
• Confusing absolute and relative growth rate. The same absolute gain gives a higher relative rate in the smaller organ.
• Swapping dedifferentiation and redifferentiation. Dedifferentiation regains the ability to divide; redifferentiation loses it again.
• Calling ethylene only a promoter. NCERT says it can fit either group but is largely a growth inhibitor.
• Saying ABA opens stomata. It stimulates stomatal closure.
• Saying cytokinins cause apical dominance. Apical dominance is described under auxins (the growing apical bud inhibits lateral buds); cytokinins help overcome it.
• Saying auxins only prevent abscission. They prevent early fruit and leaf drop but promote abscission of older, mature leaves and fruits.
• Revising photoperiodism and vernalisation as chapter sections. They are not in the rationalised NCERT chapter or the NEET UG 2026 syllabus.

Plant Growth and Development Notes PDF and Related Pages

Download the AglaSem notes for Plant Growth and Development (key notes and important questions with answers) free: View PDF

• All chapters: NEET Biology notes
• Full topic list: NEET syllabus
• Practice: NEET question papers
• Source text: NCERT Chapter 13 (NCERT, Class 11 Biology)

NEET Biology Notes: All Chapters

Botany

• The Living World
• Biological Classification
• Plant Kingdom
• Cell: The Unit of Life
• Plant Growth and Development
• Anatomy of Flowering Plants
• Cell Cycle and Cell Division
• Respiration in Plants
• Photosynthesis in Higher Plants
• Morphology of Flowering Plants
• Principles of Inheritance and Variation
• Microbes in Human Welfare
• Sexual Reproduction in Flowering Plants
• Molecular Basis of Inheritance
• Organisms and Populations
• Ecosystem
• Biodiversity and Conservation

Zoology

• Animal Kingdom
• Biomolecules
• Breathing and Exchange of Gases
• Excretory Products and their Elimination
• Body Fluids and Circulation
• Structural Organisation in Animals
• Locomotion and Movement
• Reproductive Health
• Chemical Coordination and Integration
• Neural Control and Coordination
• Evolution
• Human Health and Disease
• Human Reproduction
• Biotechnology and its Applications
• Biotechnology: Principles and Processes

All chapters with their notes PDFs are on the NEET Biology notes page.

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