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

Arithmetic growth is represented by a ______ curve, whereas geometric growth gives a ______ curve:

Accepted Answer

Linear; sigmoid (S-shaped). Arithmetic growth (constant rate) → linear plot; geometric growth (exponential then plateau under limits) → sigmoid.

Question 12

Growth is an ______ event, so it can be measured by increase in fresh weight, dry weight, length, area, volume or cell number:

Accepted Answer

Irreversible and permanent. Growth is defined as an irreversible, permanent increase in size, measurable by several parameters.

Question 13

The synthetic auxin 2,4-D is used as a ______ because it kills ______ selectively:

Accepted Answer

Herbicide (weedicide); dicot weeds. 2,4-D selectively kills dicotyledonous weeds without harming mature monocots — a common broad-leaf herbicide.

Question 14

Auxin promotes cell elongation according to the acid-growth hypothesis by:

Accepted Answer

Loosening the cell wall (increasing its extensibility). Auxin activates wall-loosening (acidification via H⁺ pumping), allowing turgor-driven elongation.

Question 15

In the brewing/malting industry, gibberellins are used to speed up:

Accepted Answer

The malting process (hydrolysis of starch via α-amylase in barley). GA induces α-amylase synthesis in germinating barley, speeding malting for the brewing industry.

Question 16

The natural cytokinin found in plants, synthesised in regions of rapid division such as root apices and developing seeds, is:

Accepted Answer

Zeatin. Zeatin (from maize kernels) is a natural cytokinin; kinetin is a synthetic/degradation product, not naturally in plants.

Question 17

ABA is also called the ______ because it promotes abscission and the ______ (dormancy of buds/seeds before winter):

Accepted Answer

Dormin; dormancy. ABA was earlier called "dormin" for its role in inducing bud and seed dormancy and promoting abscission.

Question 18

Ethylene promotes rapid internode/petiole elongation in deep-water rice plants, allowing leaves to stay above water; this is because ethylene:

Accepted Answer

Enhances the elongation of submerged internodes. In deep-water rice, ethylene stimulates internode elongation so the plant grows out of rising water (an exception to its usual growth-inhibiting/thickening effect).

Question 19

Interrupting the long dark period of a short-day plant with a flash of light will:

Accepted Answer

Prevent flowering. A light break during the critical dark period stops flowering in short-day plants — confirming the dark period is decisive.

Question 20

Vernalisation prevents precocious flowering and allows plants like winter varieties of wheat to flower in ______ by ______:

Accepted Answer

Spring; exposing seedlings/seeds to a period of low temperature. Cold treatment of germinating seeds/seedlings (vernalisation) enables winter varieties to flower in the next spring/summer.

Plant Growth and Development — NEET Biology MCQs with Solutions

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Sample questions with solutions