Plant Growth and Development NEET PYQReal NEET & AIPMT 2006–2021 questions, year-tagged, with solutions
By the RankUp team, founded by Dr. Deepak Sahu (MBBS Gold Medalist, NEET PG AIR 1731) · Updated
Every Plant Growth and Development question from the NEET & AIPMT papers on this site (2006–2021), newest first. Each is tagged with its paper. Tap an option to check your answer and read the explanation.
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Plant Growth and Development previous year questions
25 questions. Tap an option to check your answer.
Q1NEET 2021
Plants follow different pathways in response to environment or phases of life to form different kinds of structures. This ability is called :
Not quite — the answer is C.
The ability of plants to follow different developmental pathways in response to environment or phase of life, as in heterophylly of cotton or buttercup, is called plasticity. Flexibility and elasticity are not the botanical terms used for this.
Q2NEET 2021
The plant hormone used to destroy weeds in a field is :
Not quite — the answer is C.
2,4-D is a synthetic auxin widely used as a herbicide to kill broad-leaved dicot weeds, leaving monocot crops unharmed. IAA and IBA are natural auxins and NAA is used mainly for rooting and preventing fruit drop.
Q3NEET 2020 · Q2
The process of growth is maximum during:
Not quite — the answer is A.
In the sigmoid growth curve the log (exponential) phase shows the fastest growth because all the cells keep dividing. Growth is slow in the lag phase, slows and stops at senescence, and is suspended during dormancy.
Q4NEET 2020 · Q64
Name the plant growth regulator which upon spraying on sugarcane crop, increases the length of stem, thus increasing the yield of sugarcane crop.
Not quite — the answer is B.
Spraying gibberellins on sugarcane elongates the stem internodes, raising the yield by as much as 20 tonnes per acre. Cytokinins promote cell division, ethylene ripening and senescence, and ABA dormancy, so none of them lengthens the stem.
Q5NEET 2019 · Q167
It takes very long time for pineapple plants to produce flowers. Which combination of hormones can be applied to artificially induce flowering in pineapple plants throughout the year to increase yield ?
Not quite — the answer is A.
Auxins (such as NAA) induce flowering in pineapple, and ethylene also promotes synchronised flowering in pineapple. Abscisic acid is a growth inhibitor and would not promote flowering.
Q6NEET 2017 · Q88
Fruit and leaf drop at early stages can be prevented by the application of:
Not quite — the answer is C.
Auxins such as NAA prevent premature drop of fruits and leaves, while they promote abscission of older mature leaves and fruits. Ethylene does the opposite and promotes abscission.
Q7NEET 2017 (Gujarati paper) · Q80
Match Column-I with Column-II and select the correct option using codes given below. Column-I: (a) Cytokinin (b) Ethylene (c) Gibberellin (d) Abscisic acid Column-II: (i) stimulates closure of stomata (ii) increases stem length (iii) promotes lateral shoot growth (iv) found in large amount in tissues undergoing senescence
Not quite — the answer is D.
Cytokinins overcome apical dominance and promote lateral shoot growth; ethylene is produced in large amounts by senescing tissues and ripening fruits; gibberellins cause stem elongation; abscisic acid stimulates stomatal closure. The trap code giving ethylene the stem-elongation role confuses it with gibberellin.
Q8NEET 2017 (Gujarati paper) · Q110
Growth hormone Auxin was isolated by F.W. Went from tips of seedling coleoptile of:
Not quite — the answer is C.
F.W. Went isolated auxin from the coleoptile tips of oat (Avena sativa) seedlings using agar blocks. Maize, wheat and rice coleoptiles were not used in his classic experiment.
Q9NEET 2016 Phase 2 · Q110
You are given a tissue with its potential for differentiation in an artificial culture. Which of the following pairs of hormones would you add to the medium to secure shoots as well as roots?
Not quite — the answer is B.
In tissue culture the auxin to cytokinin ratio controls organ formation: a higher auxin ratio favours roots and a higher cytokinin ratio favours shoots, so both are needed to obtain shoots and roots. Gibberellin and abscisic acid do not drive this organ differentiation.
Q10NEET 2016 Phase 1 · Q113
The Avena curvature is used for bioassay of:
Not quite — the answer is C.
In the Avena curvature test, an agar block containing auxin placed on one side of a decapitated oat coleoptile causes bending proportional to auxin concentration, so it is the bioassay for IAA. Gibberellins are assayed by dwarf pea/maize or barley endosperm tests instead.
Q11AIPMT 2015
Typical growth curve in plants is:
Not quite — the answer is B.
Plant growth passes through a slow lag phase, a fast exponential (log) phase and a stationary phase, giving an S-shaped or sigmoid curve when plotted against time.
Q12AIPMT 2015
What causes a green plant exposed to the light on only one side, to bend toward the source of light as it grows?
Not quite — the answer is A.
Auxin moves away from light to the shaded side, where it makes cells elongate more, so the shoot bends toward the light. The lighted side grows less, not faster, and 'seeking light' only names the response without explaining it.
Q13AIPMT 2014
Which one of the following growth regulators is known as 'stress hormone'?
Not quite — the answer is D.
Abscisic acid increases plant tolerance to stresses such as drought, for example by closing stomata, so it is called the stress hormone. Ethylene is a ripening/senescence hormone, and GA₃ and IAA are growth promoters.
Q14AIPMT 2014
Dr. F. Went noted that if coleoptile tips were removed and placed on agar for one hour, the agar would produce a bending when placed on one side of freshly-cut coleoptile stumps. Of what significance is this experiment?
Not quite — the answer is A.
Went's Avena curvature test showed that a diffusible substance collected in agar from coleoptile tips causes bending in proportion to its amount, so it became a bioassay for quantitative estimation of small amounts of auxin. It did not identify the substance chemically as IAA or demonstrate polar transport.
Q15NEET 2013
During seed germination its stored food is mobilized by
Not quite — the answer is D.
In germinating cereal grains, gibberellin from the embryo induces the aleurone layer to make hydrolytic enzymes such as α-amylase, which mobilise stored starch. ABA has the opposite effect and promotes dormancy.
Q16AIPMT 2012 Mains
Which one of the following generally acts as an antagonist to gibberellins ?
Not quite — the answer is C.
ABA promotes dormancy and inhibits growth, so it generally opposes gibberellins, which break dormancy and promote germination and elongation. Zeatin (a cytokinin) and IAA (an auxin) are growth promoters.
Q17AIPMT 2010 Mains · Q29
One of the commonly used plant growth hormone in tea plantations is
Not quite — the answer is D.
Auxins such as IAA are used in tea plantations, where shoot tips are removed to break auxin-driven apical dominance and get bushy growth, and auxins are applied to make stem cuttings root for propagation. Ethylene and ABA are not used commercially there in this way.
Q18AIPMT 2010 Prelims · Q162
Phototropic curvature is the result of uneven distribution of
Not quite — the answer is A.
Under one-sided light, auxin builds up on the shaded side of the shoot tip, and those cells elongate more, so the shoot bends towards the light. This was shown in the coleoptile experiments of Darwin and Went. Phytochrome is a light-sensing pigment linked to flowering and germination, not the growth hormone that causes the curvature.
Q19AIPMT 2009 Prelims · Q71
One of the synthetic auxin is:
Not quite — the answer is D.
NCERT states that IAA and IBA have been isolated from plants, whereas NAA (naphthalene acetic acid) and 2,4-D are synthetic auxins. GA is a gibberellin, not an auxin.
Q20AIPMT 2009 Prelims · Q144
Which one of the following acids is a derivative of carotenoids?
Not quite — the answer is C.
Abscisic acid is a sesquiterpene formed from the breakdown of carotenoids (xanthoxin pathway). IAA and IBA are indole compounds derived from tryptophan, and gibberellic acid is a diterpene not derived from carotenoids.
Q21AIPMT 2007 Prelims · Q200
"Foolish seedling" disease of rice led to the discovery of
Not quite — the answer is D.
Kurosawa found that rice seedlings infected by the fungus Gibberella fujikuroi grew abnormally tall (bakanae or foolish seedling disease) because of a substance later named gibberellin (GA). IAA was discovered from oat coleoptile experiments and ABA from studies of abscission and dormancy.
Q22AIPMT 2006 Prelims · Q104
Parthenocarpic tomato fruits can be produced by :
Not quite — the answer is B.
Auxins and gibberellins can make the ovary grow into a fruit without fertilisation, giving seedless (parthenocarpic) tomatoes. Removing the androecium alone only stops pollination; without a hormone stimulus the flower would simply drop.
Q23AIPMT 2006 Prelims · Q105
How does pruning help in making the hedge dense ?
Not quite — the answer is B.
The shoot apex makes auxin that suppresses the lateral buds (apical dominance). Pruning removes the apex, so axillary buds grow into branches and the hedge becomes bushy. The apical shoot does not grow faster; it is the part that is removed.
Q24AIPMT 2006 Prelims · Q110
Farmers in a particular region were concerned that pre-mature yellowing of leaves of a pulse crop might cause decrease in the yield. Which treatment could be most beneficial to obtain maximum seed yield ?
Not quite — the answer is B.
Cytokinins delay leaf senescence by keeping chlorophyll and protein from breaking down, and a small dose of nitrogen supports this, so leaves stay green and photosynthesise longer for seed filling. Iron and magnesium help chlorophyll synthesis but do not stop natural senescence-type yellowing.
Q25AIPMT 2006 Prelims · Q190
An enzyme that can stimulate germination of barley seeds is :
Not quite — the answer is A.
Gibberellin from the embryo makes the aleurone layer produce α-amylase, which breaks starch into sugars for the growing seedling. This is the basis of using GA in malting barley.
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