11 interactive concept widgets for Plant Growth and Development. Drag any slider, change any number, and watch the formula and the answer update live. Built so you understand how each NEET problem actually works, not just the final number.
On this page
Click each of the three growth zones at a root tip to see cell state, examples, and where the zones overlap. Watch the cells become rectangular as you move from the meristem to the elongation zone, and see root hairs in the maturation zone.
Plant growth happens in three distinct zones at the root or shoot tip. Click each zone to see cell state, examples, and how the zones overlap.
Meristematic Zone
Position: At the very tip (root apex / shoot apex)
Cells divide rapidly. They are small, thin-walled, with dense protoplasm and prominent nuclei. This is the source of all new cells.
Cell state:
• Small, isodiametric (cube-shaped)
• Thin primary walls
• Dense cytoplasm with prominent nucleus
• High mitotic activity
• No vacuoles or very small vacuoles
Where to find it:
• Root apical meristem (covered by root cap)
• Shoot apical meristem (apex of stem)
• Cells with active mitosis
NEET key facts
!
Three growth phases: meristematic → elongation → maturation. (Also called the three zones in roots.)
!
Meristematic phase: cells DIVIDE actively. Small cells, dense protoplasm, no vacuoles.
!
Elongation phase: cells STRETCH (take up water in central vacuole). Most of the actual length increase happens here.
!
Maturation phase: cells DIFFERENTIATE into specific tissues (vessels, sieve tubes, root hairs).
!
Root cap PROTECTS the meristematic zone (covers the root tip).
Try this
Compare the two main growth patterns. Adjust initial size, rate, and time. See how arithmetic growth gives a straight line and geometric growth gives a J-curve. Side-by-side comparison panel.
Compare the two main growth patterns. In arithmetic growth, only one daughter cell divides further. In geometric (exponential) growth, both divide. Adjust initial size, rate, and time to see how they differ.
Initial size (L0): 10
Growth rate (r): 2
Time (t): 10
Final size at t = 10
30.00
L = 10 + 2 × 10 = 30.00
Arithmetic vs Geometric: side by side
Arithmetic
• Only ONE daughter cell divides further
• Constant rate of growth
• Linear (straight-line) graph
• Formula: Lt = L0 + r·t
• Example: root growing at constant rate
Geometric / Exponential
• BOTH daughter cells divide further
• Rate ∝ current size
• Exponential (J-shaped) graph
• Formula: W1 = W0 · e^(r·t)
• Example: log phase of growth, bacterial culture
NEET key facts
!
Arithmetic growth: only ONE daughter cell continues to divide; rate is constant; linear curve.
!
Geometric growth: BOTH daughter cells continue to divide; rate is proportional to current size; exponential curve.
!
Arithmetic formula: Lt = L0 + r·t. Geometric formula: W1 = W0 · e^(r·t).
!
Absolute growth rate: per unit time. Relative growth rate: per unit size per unit time (allows fair comparison of small and big organs).
!
Real organisms show geometric growth in log phase (resources abundant) and arithmetic / stationary as they reach limits.
Try this
Drag the time slider to scrub through the three phases (lag, log, stationary) of the universal sigmoid growth curve. Watch the marker move along the S-curve and the highlighted phase change.
Drag the time slider to scrub through the three phases of growth. Watch the marker move along the S-curve and the active phase highlight.
Time on growth curve: 50 (0 to 100)
Log / Exponential phase
When: Middle of growth
Rapid growth as both daughter cells of every division also divide. Resources are abundant. The growth rate is at its maximum.
Characteristics:
• Maximum rate of growth
• Both daughter cells divide (geometric / exponential)
• Steepest slope of the S-curve
• Doubling time is shortest in this phase
Why: Resources (water, nutrients, light) are abundant. No competition or limitation yet. Cells double in number rapidly.
NEET key facts
!
Sigmoid curve = S-shaped curve = typical growth curve. Three phases: lag, log (exponential), stationary.
!
Lag phase: slow initial growth, cells preparing.
!
Log phase: rapid growth, geometric / exponential, both daughter cells divide.
!
Stationary phase: growth slows due to limited resources, cells reach equilibrium.
!
The exponential phase represents geometric growth; lag and stationary represent natural slowing.
Try this
Three closely related but distinct processes. Click each to see cell state changes, examples, and how they show plant cell totipotency.
Three closely related but distinct processes. Click each to see the cell state changes, examples, and how they show plant cell totipotency.
Differentiation
Meristematic → Mature specialised
Meristematic cells (which divide actively) develop into permanent specialised cells. They lose the capacity to divide and gain specific functions. For example, meristematic cells become tracheary elements (vessels, tracheids), losing protoplasm to function as efficient water conductors.
Cell state: Cell becomes mature, specialised, often non-dividing
Examples:
• Meristem → Vessels and tracheids (water conduction; cells lose protoplasm)
• Meristem → Sieve tubes (food conduction; remain alive but lose nucleus)
• Meristem → Sclerenchyma (mechanical strength; thick lignified walls)
• Meristem → Parenchyma (storage; living cells with thin walls)
• Meristem → Cork cells (protective; suberised walls, lose protoplasm)
Plant cell totipotency
Plant cells are totipotent: every cell carries the genetic information to make a whole new plant. Dedifferentiation is the process by which this totipotency is realised. Tissue culture relies on this: a small piece of any plant tissue can be made to dedifferentiate into callus and then redifferentiate into a complete plant.
NEET key facts
!
Differentiation: meristematic cells → mature specialised cells (e.g., vessels, tracheids, sclerenchyma).
!
Dedifferentiation: mature cells regain dividing capacity (cork cambium from cortex, callus in tissue culture).
!
Redifferentiation: dedifferentiated cells specialise again (secondary xylem/phloem from cambium).
!
Plant cells are TOTIPOTENT (any cell can make a new plant). Dedifferentiation demonstrates this.
!
Dead conducting cells (vessels, tracheids) lose their protoplasm during differentiation - this is irreversible.
Try this
Click any of the 5 PGRs (auxin, gibberellin, cytokinin, ABA, ethylene) to explore its discoverer, source, effects, applications, and NEET traps. Includes a quick reference table.
Click any of the 5 PGRs (auxin, gibberellin, cytokinin, ABA, ethylene) to explore its discoverer, source, effects, applications, and NEET traps.
Auxin (IAA)
Type: Growth-promoting
Discovery
By: Charles Darwin & Francis Darwin (1880, phototropism); F.W. Went (1928, isolation)
From: Coleoptile tips of Avena (oats)
Natural forms
IAA (indole-3-acetic acid), IBA (indole butyric acid)
Biological effects
• Cell elongation (especially in coleoptiles and stems)
• Apical dominance (suppresses lateral buds)
• Phototropism and geotropism (uneven distribution causes bending)
• Initiation of adventitious roots in stem cuttings
• Promotes parthenocarpy (seedless fruit development)
• Xylem differentiation
Agricultural / Commercial uses
• 2,4-D as broadleaf weedicide (kills dicots, spares monocots like wheat)
• NAA / IBA for rooting in stem cuttings
• Prevent fruit and leaf drop (sprayed before harvest)
• Induce parthenocarpy in tomato
• Promotes flowering in pineapples
NEET FAVOURITE FACTS
• Auxin was the FIRST plant hormone to be discovered.
• Apical dominance is the classic auxin effect; cytokinin counteracts it.
• 2,4-D is a synthetic auxin and a popular weedicide.
Quick reference: discoverers and sources
Auxin
Charles Darwin & Francis Darwin
Coleoptile tips of Avena (oats)
Gibberellin
Eiichi Kurosawa
Gibberella fujikuroi (a fungus that causes "bakanae" / foolish seedling in rice)
Cytokinin
Skoog and Miller
Autoclaved herring sperm DNA (kinetin); coconut milk and corn kernels (zeatin)
Abscisic Acid
Wareing
Cotton bolls, sycamore leaves
Ethylene
H.H. Cousins
Detected first in coal gas; produced naturally by ripening fruits
Try this
Click through the 6 famous experiments that led to the discovery of auxin. Watch how each experiment narrowed down the source, nature, and identity of the bending signal.
Click through the 6 famous experiments that led to the discovery of auxin. From Darwin (1880) to Went (1928), each experiment narrowed down the source, nature, and identity of the bending signal.
Charles & Francis Darwin (1880)
Setup:
Coleoptile of canary grass exposed to one-sided light. Tip intact.
Observation:
Coleoptile bends towards the light.
Conclusion:
Coleoptile bends towards light (positive phototropism). The tip is the photoreceptive region.
The discovery of auxin: timeline
NEET key facts
!
Darwin (1880): coleoptile of canary grass / Avena bends to light. Tip senses, base bends.
!
Boysen-Jensen (1913): chemical signal (passes through gelatin, blocked by mica).
!
Paal (1919): asymmetric tip = asymmetric distribution = bending even in DARK.
!
F.W. Went (1928): isolated the chemical (named it AUXIN). Used Avena coleoptile bend test.
!
IAA (indole-3-acetic acid) was later identified as the natural auxin.
Try this
Three categories: long-day, short-day, day-neutral plants. Explore example plants for each category, then test yourself with a 10-question shuffled quiz.
Three categories of flowering plants based on day-length response: long-day, short-day, day-neutral. Click each category to see typical examples, then test yourself with the quiz.
Long-Day Plants (LDP)
Flower when day length is LONGER than a critical value (typically 12-14+ hours).
Day length > critical period → flowering
Bloom in summer (long days). Native to temperate regions.
Examples (7):
Where is the photoperiod sensed?
The LEAF is the photoperiodic sensor. The pigment phytochrome in leaves perceives the dark/light period.
Once the right photoperiod is sensed, the leaf produces a flowering signal called florigen (now identified as the FT protein in Arabidopsis). Florigen travels from the leaves to the shoot apex via the phloem and converts the apex from vegetative to flowering.
NEET trap: even ONE leaf exposed to the right photoperiod is enough to induce flowering.
NEET key facts
!
LDP (long-day): wheat, spinach, radish, barley, henbane (Hyoscyamus). Flower in summer.
!
SDP (short-day): rice, soybean, cotton, chrysanthemum, tobacco, Xanthium. Flower in autumn / early winter.
!
DNP (day-neutral): tomato, cucumber, sunflower, maize. Flower based on age, not day length.
!
Photoperiod is sensed by LEAVES (via phytochrome). Florigen / FT protein travels from leaves to shoot apex.
!
It is actually the LENGTH OF THE DARK PERIOD that matters, not the day length. (A flash of light in the middle of the night can disrupt SDP flowering.)
Try this
Toggle between plants and watch the flowering outcome change with or without the cold treatment. Includes mechanism panel with epigenetic FLC silencing.
Some plants require a cold period to flower. Toggle between plants and watch the flowering outcome change with or without the cold treatment.
Cold treatment given?
✓ Plant flowers
Reason: Cold treatment was given (vernalisation requirement met). Plant senses winter has passed and triggers flowering.
Real life: If sown in spring (skipping winter), winter wheat stays vegetative and does NOT flower - the cold trigger is missing.
About Winter wheat
Sown in autumn (October-November). Seedlings experience winter cold. Vernalisation requirement is met. They flower in spring and ripen by summer.
Examples: Winter wheat (Triticum) varieties grown in temperate regions
Where is vernalisation sensed?
Vernalisation is sensed by the shoot apical meristem (SAM), NOT by leaves. (Photoperiodism, in contrast, is sensed by leaves.)
The cold treatment causes epigenetic silencing of a flowering-repressor gene (FLC, FLOWERING LOCUS C in Arabidopsis). Once silenced, the plant can flower when day length and temperature are right. The effect is remembered through cell divisions.
NEET key facts
!
Vernalisation = COLD TREATMENT (1-7 degrees Celsius) required to induce flowering.
!
Plants requiring vernalisation: winter wheat, rye, barley (sown autumn, flower spring); biennials (cabbage, carrot, beetroot, sugar beet).
!
Without cold treatment, these plants stay vegetative and do NOT flower.
!
Vernalisation is sensed at the SHOOT APICAL MERISTEM (NOT leaves). Photoperiod is sensed by leaves.
!
Vernalisation can be artificially supplied to seeds for off-season cultivation.
!
NEET trap: vernalisation = cold; photoperiodism = day length. These are SEPARATE flowering controls.
Try this
Pick a cause of dormancy, then pick a treatment, and see whether the treatment will actually work for that cause. Cause-method matching reference table.
Seeds often refuse to germinate even when conditions look favourable. Pick a cause of dormancy, then pick a treatment, and see whether the treatment will actually work for that cause.
1. Pick a CAUSE of dormancy:
Impermeable seed coat
Hard, water-impermeable seed coat (testa) prevents water and oxygen from reaching the embryo. The embryo cannot germinate even with favourable conditions.
Examples:
• Hard-coated legumes (Acacia)
• Lotus seeds (can stay dormant for centuries)
• Many wild grasses
2. Pick a METHOD to break dormancy:
Scarification
Mechanically or chemically damaging the seed coat to allow water and oxygen entry. Methods: rubbing with sandpaper, treatment with concentrated sulphuric acid, hot water soaking.
✓ Will work!
Scarification addresses the impermeable seed coat problem. The seed will germinate.
Cause-method matching reference
Impermeable seed coat
→
Scarification
Chemical inhibitors
→
Stratification
, Gibberellin (GA) treatment
, Leaching / washing
Immature embryo
→
Unfavourable physiological state
→
Stratification
, Gibberellin (GA) treatment
NEET key facts
!
Seed dormancy: a state where viable seeds do NOT germinate even in favourable conditions.
!
Causes: impermeable seed coat, chemical inhibitors (ABA), immature embryo, unfavourable physiological state.
!
Methods to break dormancy: scarification (for hard coats), stratification (cold-moist for chilling requirement), gibberellin (antagonises ABA), leaching (washes out inhibitors).
!
ABA promotes dormancy. GA breaks dormancy. The GA / ABA ratio decides germination.
!
Lotus seeds have shown viability after 1300+ years (impermeable coat enables long dormancy).
Try this
16 effects to match to their hormones. Includes auxin (apical dominance, parthenocarpy, rooting), gibberellin (bolting, amylase), cytokinin (Richmond-Lang), ABA (stress, dormancy), and ethylene (ripening, ethephon).
For each effect, click the hormone that causes it. Check your answers when done.
Match 0 / 16 done
Alpha-amylase synthesis in barley
Bolting in rosette plants
Rooting in stem cuttings
Stress hormone (drought, salinity)
Climacteric fruit ripening
Ethephon (slow release in fruits)
Sugarcane yield boost (20 t/acre)
Stomatal closure during drought
Phototropism (uneven distribution)
Flowering in pineapples
Parthenocarpy
Apical dominance
Delayed senescence (Richmond-Lang effect)
Cell division in tissue culture
Seed dormancy
Lateral bud growth (counters apical dominance)
Try this
12-question scored NEET quiz covering growth definition, sigmoid curve, plant growth regulators (auxin, GA, cytokinin, ABA, ethylene), photoperiodism, and vernalisation.
One question at a time. Pick an option, see the explanation, then move to the next.
Plant growth is best defined as:
A. A reversible increase in size
B. An irreversible permanent increase in size, mass, or volume
C. Any change in form
D. Cell division alone
Drag, slide and recompute on the next chapter's widgets.
You've reached the end of Botany Class 11.
Move on to Class 12 below, or restart from Class 11 Chapter 1 to revise the basics.
Respiration in Plants
Sexual Reproduction in Flowering Plants
Free 14-day trial. AI tutor, full mock tests and chapter analytics — built for NEET 2027.
Free 14-day trial · No credit card required