Question 1

Growth in plants is largely restricted to specialised regions of active cell division called:

Accepted Answer

Meristems. Meristematic tissues (apical, lateral, intercalary) retain the capacity to divide, giving plants indeterminate growth.

Question 2

The three phases of growth in a cell/tissue are, in order:

Accepted Answer

Meristematic → elongation → maturation. Cells first divide (meristematic), then enlarge (elongation), then differentiate (maturation).

Question 3

The first plant hormone to be discovered, isolated from oat coleoptile tips, was:

Accepted Answer

Auxin. Auxin (IAA) was the first hormone discovered, following Darwin and F.W. Went's coleoptile experiments.

Question 4

The suppression of the growth of lateral (axillary) buds by the shoot apex is called:

Accepted Answer

Apical dominance. Auxin produced at the shoot apex inhibits lateral buds — apical dominance (removed by decapitation).

Question 5

The hormone that causes "bolting" (rapid internode/stem elongation before flowering) in rosette plants is:

Accepted Answer

Gibberellin. Gibberellins (e.g. GA₃) cause bolting — internode elongation in rosette plants like cabbage.

Question 6

Cytokinins are hormones that mainly promote:

Accepted Answer

Cell division (cytokinesis). Cytokinins promote cytokinesis (cell division) and were first identified as kinetin from herring sperm DNA.

Question 7

The hormone known as the "stress hormone", which promotes stomatal closure during water stress, is:

Accepted Answer

Abscisic acid (ABA). ABA closes stomata under drought stress and is a general growth inhibitor.

Question 8

The gaseous plant hormone that promotes fruit ripening is:

Accepted Answer

Ethylene. Ethylene is the only gaseous hormone; it hastens ripening and senescence.

Question 9

The response of plants to the relative lengths of day and night (which affects flowering) is called:

Accepted Answer

Photoperiodism. Photoperiodism is the dependence of flowering on the duration of light/dark periods.

Question 10

The promotion of flowering by a period of low temperature (cold treatment) is called:

Accepted Answer

Vernalisation. Vernalisation is the low-temperature requirement for flowering in some plants (e.g. winter wheat).

Question 11

A plant can keep growing throughout its life because it retains regions of perpetually dividing cells at root and shoot tips. This ability of plants to grow indefinitely is termed:

Accepted Answer

Indeterminate (open form of) growth. The presence of meristems retaining the capacity to divide throughout life gives plants an open (indeterminate) form of growth, unlike the determinate growth typical of animals.

Question 12

While studying a leaf, a student notes that its cells are fully mature and no longer divide, yet earlier they had divided and then elongated. The cells are currently in which phase of growth?

Accepted Answer

Phase of maturation. After the meristematic (division) and elongation phases, cells attain their final size and functional maturity in the phase of maturation, where differentiation is completed.

Question 13

An instrument used in the laboratory to measure linear increase in the length of a plant shoot over time is the:

Accepted Answer

Auxanometer. An auxanometer measures growth (increase in length) of a shoot; a potometer measures transpiration/water uptake and a porometer measures stomatal opening.

Question 14

A single leaf of a plant may show different leaf shapes on the same plant depending on whether it develops in air or under water, as in Buttercup. This ability of a genotype to produce different forms in response to environment is called:

Accepted Answer

Plasticity. Plasticity is the ability of plants to follow different developmental pathways in different environments; heterophylly in Buttercup, Cotton and Coriander is a classic example.

Question 15

A gardener removes the shoot tips of a hedge to make it grow bushier and denser. The physiological basis of this practice is that decapitation:

Accepted Answer

Removes the source of auxin, releasing lateral buds from apical dominance. The shoot apex is the auxin source that suppresses lateral buds; removing it lowers auxin at the buds so they sprout, making the plant bushy.

Question 16

In horticulture, auxins such as IBA and NAA are commonly applied to the cut ends of stem cuttings mainly to:

Accepted Answer

Promote initiation of adventitious roots. Auxins promote rooting, so IBA/NAA are applied to cuttings to induce adventitious root formation for vegetative propagation.

Question 17

Auxin sprayed on tomato or grape flowers can produce seedless fruits without fertilisation. This induction of fruit development is called:

Accepted Answer

Parthenocarpy. Auxin can induce parthenocarpy — the development of fruit without fertilisation, yielding seedless fruits.

Question 18

A weed-killer that selectively destroys broad-leaved dicot weeds in a lawn of narrow-leaved monocot grasses is the synthetic auxin:

Accepted Answer

2,4-D. 2,4-D is a synthetic auxin used as a selective herbicide that kills dicot (broad-leaved) weeds while leaving mature monocots relatively unaffected.

Question 19

The most extensively studied and commercially important gibberellin, widely referred to in agriculture, is:

Accepted Answer

GA3 (gibberellic acid). Of the many gibberellins, GA3 (gibberellic acid) is the most intensively investigated and commonly used form.

Question 20

Spraying sugarcane with gibberellin increases yield because gibberellin:

Accepted Answer

Elongates the stem, so more sugar-storing internode tissue is produced. Sugar is stored in the stem; GA-induced stem elongation gives longer canes and thus a substantial increase in sugar yield.

Plant Growth and Development — NEET Biology MCQs with Solutions

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Sample questions with solutions