Plant Growth and Development carries 4.0 of 100 Botany marks in NEET by past-paper share: 32 of the 793 tagged NEET Botany PYQs in the ViJEEta bank (NEET 2013–2026). It ranks 13 of 21 Botany chapters.
How the weight is computed: this chapter's tagged NEET PYQs divided by all tagged NEET Botany PYQs in the bank (32 of 793), times 100, with repeated questions counted once. The bank does not store the year of each NEET question, so none is printed. Computed from the bank at build time. Updated 19 Oct 2026.
16 facts the paper keeps asking, each with how it is asked. Copy it onto one page of your notebook: that page is this chapter's handbook.
Growth is an irreversible, permanent increase in size of a cell, organ or individual; it is driven by metabolism and uses energy, and a leaf expanding counts as growth.
Asked as: Which is not growth? Wood swelling in water, because that is reversible.
Plants have open (indeterminate) growth because meristems keep adding new cells. Lateral meristems (vascular cambium, cork cambium) give secondary growth (girth) in dicots and gymnosperms.
Asked as: Why can plant growth be unlimited? Because meristems persist and self-perpetuate.
A maize root apical meristem makes more than new cells per hour (growth as cell number). Watermelon cells enlarge up to times (growth as cell size). Pollen tube growth is measured by length, and dorsiventral leaf growth by surface area.
Asked as: Match the system to its growth parameter (maize root, watermelon, pollen tube, leaf).
There are three phases of growth: meristematic, elongation and maturation. Meristematic cells are rich in protoplasm, have large nuclei, and have thin cellulosic primary walls with abundant plasmodesmata. Elongation cells show more vacuolation, cell enlargement and new wall deposition.
Asked as: In which zone do cells show increased vacuolation? The elongation zone.
In arithmetic growth only one daughter cell keeps dividing. It follows , and a root elongating at a constant rate gives a linear curve.
Asked as: Which growth gives a straight-line curve of length against time?
In geometric growth both daughter cells keep dividing. It passes through lag, log (exponential) and stationary phases, giving a sigmoid (S) curve, which is typical of living things in a natural environment.
Asked as: Why does growth reach the stationary phase? Because nutrient supply is limited.
Exponential growth follows , where is the relative growth rate, also called the efficiency index.
Asked as: What is in the exponential growth equation called?
Absolute growth rate is total growth per unit time. Relative growth rate is growth per unit time per unit initial parameter. Leaves A and B both gain , so the smaller leaf has the higher relative rate.
Asked as: Which leaf shows the higher relative growth rate, and why?
A tracheary element differentiates by losing its protoplasm and laying down lignocellulosic secondary walls. Dedifferentiation is when living differentiated cells regain the ability to divide, e.g. parenchyma forming interfascicular cambium and cork cambium.
Asked as: Formation of cork cambium from parenchyma is an example of what?
Plasticity is development following different pathways. Heterophylly in cotton, coriander and larkspur is juvenile versus mature leaves. In buttercup it is leaves in air versus leaves in water, which is caused by the environment.
Asked as: Heterophylly in buttercup is due to what? The environment, not the phase of life.
PGRs differ in chemical nature: IAA is an indole, kinetin is an adenine (purine) derivative, ABA is a carotenoid derivative, is a terpene, and ethylene is a gas.
Asked as: Match the PGR to its chemical nature.
Discoveries: the Darwins saw canary grass coleoptiles bend to light, and F.W. Went isolated auxin from oat coleoptile tips. E. Kurosawa (1926) studied bakanae of rice caused by \textit{Gibberella fujikuroi}. F. Skoog and co-workers found tobacco callus grew only with auxin plus vascular extract, yeast extract, coconut milk or DNA, and Miller et al. (1955) later identified and crystallised the active substance, kinetin. Inhibitor-B, abscission II and dormin turned out to be the same compound, ABA. H.H. Cousins (1910) confirmed that ripened oranges release a volatile substance that hastened ripening of stored unripe bananas; it was identified as ethylene only later.
Asked as: Match the scientist or disease to the PGR.
Auxin was first isolated from human urine. IAA and IBA are natural, while NAA and 2,4-D are synthetic. Auxins root stem cuttings, induce flowering in pineapple, cause apical dominance and give parthenocarpy in tomato. 2,4-D kills dicot weeds but spares mature monocots.
Asked as: Which PGR would you use to induce rooting in a twig, or to make a weed-free lawn?
There are more than gibberellins, and all are acidic. They lengthen grape stalks, elongate apples, delay senescence, speed up malting with , and raise sugarcane yield by up to tonnes per acre. They also cause bolting in beet and cabbage.
Asked as: Which PGR would you use to bolt a rosette plant?
Kinetin came from autoclaved herring sperm DNA and does not occur naturally in plants. The natural cytokinin zeatin comes from corn kernels and coconut milk. Cytokinins overcome apical dominance and delay leaf senescence through nutrient mobilisation.
Asked as: Which PGR would you use to delay leaf senescence or grow axillary buds?
Ethylene ripens fruit by raising respiration (the respiratory climacteric). It also gives the apical hook in dicot seedlings, elongates internodes in deep-water rice, breaks seed and bud dormancy, and induces flowering in mango. Its source compound, ethephon, increases female flowers in cucumber. ABA is the stress hormone: it closes stomata, inhibits germination, induces seed dormancy and acts against GAs.
Asked as: Which PGR would you use to quickly ripen fruit, or to close stomata immediately?
Auxin from the apical bud causes apical dominance, and cytokinins overcome it. Decapitation (as in tea plantations and hedges) removes the auxin source, so lateral buds grow. Don't mark cytokinin as the cause.
8 real previous-year questions from this chapter, as printed in the paper, each with its worked solution. Answer the first one here with no sign-in.
Correct answer: Option D
Correct answer: Option B
Correct answer: Option C
Correct answer: Option D
Correct answer: Option D
Correct answer: Option A
Correct answer: Option C
Correct answer: Option C
All 9 topics, by tagged PYQs, then practice questions. Counted from the bank. Updated 19 Oct 2026.
| Topic | PYQs | Practice questions |
|---|---|---|
| Physiological Effects of Plant Growth Regulators | 20 | 209 |
| Plant Growth | 5 | 79 |
| Plant Growth Regulators | 2 | 35 |
| Differentiation, Dedifferentiation, and Redifferentiation | 2 | 28 |
| PhotoperiodismNot in NEET now | 2 | 12 |
| Development | 1 | 28 |
| VernalizationNot in NEET now | 0 | 8 |
| Miscellaneous Examples | 0 | 6 |
| AbscisionNot in NEET now | 0 | 1 |
Unknown is not zero. Until you answer at least 3 graded questions in Plant Growth and Development, ViJEEta shows – instead of a zero or a 50% default. Book exercises can raise chapter mastery up to 0.60, adaptive practice up to 0.75, and only a timed chapter test or mock can certify 0.80 and above.
Every chapter test is 25 questions. It starts at moderate difficulty and adapts after each saved answer. If you open a solution before answering, that attempt earns no credit, so your mastery stays honest.
Start the Plant Growth and Development test