NDA General Studies · Biology · 24 questions · 2017 to 2026
NDA Plant life previous year questions with solutions
Plant life is a small, steady part of the General Studies paper, about one question in sixty-five, one or two a sitting. Flowers, pollination, fertilisation and the fruit-and-seed sequence carry most of it; photosynthesis the rest. Every question UPSC has set on it since 2017, solved. Grouped by the method each needs, newest first; open a question for its answer and worked solution.
18.1 Photosynthesis: raw materials, the three steps, and what the leaf does with light (5)18.2 Transpiration, transport, growth and movement in plants (3)18.3 The flower and pollination (5)18.4 Fertilisation: the pollen tube, the ovule and double fertilisation (5)18.5 Fruit, seed, germination and vegetative propagation (6)
18.1 Photosynthesis: raw materials, the three steps, and what the leaf does with light
1. NDA 2024 (I)
Leaves of most plants appear green because the chlorophyll present in it:
Answer and solution
Answer: (a) absorbs red and blue light while reflecting green light.
Method. absorption and reflection of light by chlorophyll
Chlorophyll absorbs mostly red and blue light and reflects (and transmits) green light, so leaves look green. Standard result (Class 10 Science ch 5, C5-A14, C5-A17, on chlorophyll in chloroplasts; the absorption spectrum is the standard Class 11 result).
2. NDA 2023 (II)
Which one of the following is NOT a requirement for photosynthesis?
Answer and solution
Answer: (d) O2
Method. requirements of photosynthesis
Chlorophyll, CO2, water and light are requirements (NCERT C5-A14). O2 is a product of photosynthesis (C5-A15), not a requirement.
3. NDA 2021 (II)
Which one of the following statements about the process of photosynthesis is correct?
Answer and solution
Answer: (c) Water molecule splits into hydrogen and oxygen.
Method. what happens in photosynthesis, by NCERT's wording
NCERT C5-A15: photosynthesis involves absorption of light energy by chlorophyll, conversion of light energy to chemical energy, splitting of water into hydrogen and oxygen, and reduction of carbon dioxide. (c) matches 'splitting of water into hydrogen and oxygen' word for word. (a) is the reverse (light energy becomes chemical energy). (b) is wrong: CO2 is reduced, not oxidised. (d) is not NCERT's wording: it is the absorbed light that is first converted to chemical energy, which then drives the splitting of water.
4. NDA 2021 (I)
The gaseous product of a process in plants is a requirement for another vital process that releases energy. Given below are four combinations of the process and product. Identify the correct answer.
Answer and solution
Answer: (c) Photosynthesis and Oxygen
Method. photosynthesis releases O2, used in aerobic respiration
Photosynthesis gives off oxygen (C5-A15, C5-A14), and aerobic respiration, the energy-releasing process, uses that oxygen to break down food (C5-A05, C5-A51). Nitric oxide is not a respiratory product, water vapour from transpiration is not needed for energy release, and germination is not a process whose CO2 is needed for respiration.
5. NDA 2018 (II)
The oxygen evolved during photosynthesis comes from splitting of
Answer and solution
Answer: (a) water
Method. source of oxygen in photosynthesis
In the light reactions water is split into hydrogen and oxygen; the oxygen is released. NCERT row C5-A15 gives 'splitting of water into hydrogen and oxygen' as a step of photosynthesis. The oxygen is not from CO2, which is reduced to carbohydrate.
18.2 Transpiration, transport, growth and movement in plants
6. NDA 2021 (II)
Shoots of plant show upward movement and it can be designated to be
Answer and solution
Answer: (d) Negatively geotropic
Method. tropic responses
Shoots grow upward, away from the earth's pull: negative geotropism (NCERT C6-A35). Shoots turn towards light (positive phototropism, C6-A34), so 'negatively phototropic' is wrong. Hydrotropism and chemotropism are growth towards water and chemicals (C6-A58, C6-A36).
7. NDA 2021 (I)
In a dicot pot herb, vaseline/vegetable oil was applied on the upper surface of one leaf (Experimental leaf 1) and on the lower surface of another leaf (Experimental leaf 2). Vaseline/Vegetable oil was not applied on the control leaf. The plant was deliberately not watered for several days. Which leaf will dry up last?
Answer and solution
Answer: (b) Experimental leaf 2
Method. stomata are more on the lower surface of a dicot leaf
In a dicot leaf most stomata are on the lower (abaxial) surface. Vaseline on the lower surface blocks most stomata and so most transpiration; Vaseline on the upper surface blocks few. Water loss: control > leaf 1 > leaf 2. Leaf 2 loses water slowest and dries up last. NCERT C5-A19 (water is lost through stomata) and C5-A20.
8. NDA 2018 (II)
Damage to the apical meristem of a growing young plant will affect the
Answer and solution
Answer: (a) length of the plant
Method. apical meristem = region of growth in length
The apical meristem at the shoot tip divides to add cells and lengthen the stem. Damage to it stops growth in length. Flower colour, leaf colour and fruit taste are set by pigments and genes, not by the apex. Standard result (Class 9 Science ch 6 on meristematic tissue; Class 10 Science ch 6, growth).
18.3 The flower and pollination
9. NDA 2026 (II)
A flower typically is composed of:
Answer and solution
Answer: (c) Carpels, Stamens, Petals, Sepals
Method. parts of a flower
A flower typically has four whorls: sepals, petals, stamens and carpels (pistil) (NCERT C7-A40, NS11-A34). Stomata, cotyledon, cambium and root cap are not parts of a flower.
10. NDA 2026 (II)
Which one of the following is not a characteristic of an insect-pollinated plant?
Answer and solution
Answer: (b) Light and small pollen grains
Method. features of insect-pollinated flowers
Insect-pollinated flowers are bright and fragrant, have nectar, and have sticky or spiny pollen (NS11-A47). Light, small pollen in large quantity is a feature of wind-pollinated plants (NS11-A45).
11. NDA 2023 (II)
Relationship between a flower and honey-bee will help the flower for/in
Answer and solution
Answer: (b) Pollination
Method. pollination by insects
A visiting honey-bee carries pollen from anther to stigma. The relationship helps the flower in pollination (NCERT C7-A46, C7-A88; NS11-A44, NS11-A47). It does not speed development or size.
12. NDA 2022 (I)
Which one of the following plants has unisexual flowers?
Answer and solution
Answer: (a) Papaya
Method. unisexual and bisexual flowers
NCERT C7-A41: papaya and watermelon have unisexual flowers; Hibiscus and mustard are bisexual. Sunflower florets are in the bisexual disc and the ray florets of the head are usually sterile or female, but the standard unisexual example is papaya.
13. NDA 2017 (I)
The colourful part of the Sunflower or Marigold plant is
Answer and solution
Answer: (b) Inflorescence
Method. structure of the capitulum (head) of Sunflower and Marigold
What looks like one big flower in sunflower or marigold is an inflorescence (capitulum): many small florets on a common disc, with colourful ray florets round the edge. So the colourful showy part is the inflorescence, not a single flower. Standard result (Class 11/12 Biology, Asteraceae; Class 10 Science ch 7 treats the flower as the unit but the head is a cluster).
18.4 Fertilisation: the pollen tube, the ovule and double fertilisation
14. NDA 2026 (I)
Which one of the following parts of an ovule possesses reserve food?
Answer and solution
Answer: (d) Nucellus
Method. reserve food in the ovule
The nucellus is the tissue that surrounds the embryo sac and holds reserve food, which feeds the embryo sac and developing embryo. The integument forms the seed coat, the funicle is the stalk and the chalaza is the basal region. Standard result (Class 12 Biology ch 2).
15. NDA 2023 (II)
In angiosperms, pollen grain germinates to produce two male gametes. Which one of the following functions is carried out by these gametes?
Answer and solution
Answer: (d) One gamete fuses with the egg cell and the other one fuses with a diploid secondary nucleus
Method. double fertilization in angiosperms
The pollen tube delivers two male gametes: one fuses with the egg cell (zygote) and the other with the diploid secondary nucleus (two polar nuclei) of the central cell, giving the triploid endosperm. Standard result (Class 12 Biology ch 2). NCERT C7-A44/45 gives the first fusion only.
16. NDA 2023 (II)
In flowering plants, DNA content of the parent plant gets halved during
Answer and solution
Answer: (d) Pollen formation
Method. meiosis halves the chromosome number at gamete formation
The pollen grain is formed from the pollen mother cell by meiosis, which halves the DNA/chromosome content of the diploid parent. Seed germination, fruit formation and flower bud formation involve mitosis or growth. Standard result (Class 12 Biology ch 2; NS11-A26 for haploid gametes after meiosis).
17. NDA 2021 (I)
In a typical flower, germinating pollen grains pass through several parts of the gynoecium before they reach the ovule. A list of the parts of gynoecium is given below in different combinations. Choose the combination that represents the correct sequence of pollen tube pathway/journey:
Answer and solution
Answer: (b) Stigma, Style, Ovary
Method. pathway of the pollen tube through the pistil
The pollen lands on the stigma, the tube grows down through the style to reach the ovary and the ovule (NCERT C7-A47, C7-A43). So the order is stigma, style, ovary. The pistil is the whole gynoecium, not a part in the sequence.
18. NDA 2018 (II)
If one set of chromosomes for a given plant is represented as N; in case of double fertilization, the zygote and the endosperm nucleus of a diploid plant would have how many sets of chromosomes respectively?
Answer and solution
Answer: (d) 2N and 3N
Method. double fertilization: zygote 2N, primary endosperm nucleus 3N
One male gamete (N) fuses with the egg (N): zygote = 2N. The other male gamete (N) fuses with the two polar nuclei (N + N) of the central cell: endosperm nucleus = 3N. Standard result (Class 12 Biology ch 2, triploid endosperm; Class 10 Science ch 7, C7-A44/C7-A45 for fertilisation).
18.5 Fruit, seed, germination and vegetative propagation
19. NDA 2026 (I)
Which part of the plant or flower contributes in the form of false fruit like apple?
Answer and solution
Answer: (d) Thalamus
Method. false fruit
In apple (a false fruit, or pome) the fleshy edible part develops from the thalamus (receptacle), not from the ovary. Petal, sepal and stamen wither. Standard result (Class 12 Biology ch 2; NCERT C7-A48 for the true fruit from the ovary).
20. NDA 2024 (II)
In which one among the following the vegetative propagation takes place through Eye Buds?
Answer and solution
Answer: (a) Potato
Method. vegetative propagation by buds ('eyes')
A potato tuber has 'eyes', which are buds; a piece with an eye sprouts into a new plant (NCERT NS11-A04, fleshy underground stems such as potato). Sugarcane propagates from stem cuttings with nodes (C7-A26), ginger from rhizome pieces, onion from bulbs.
21. NDA 2023 (II)
Which one of the following is the correct sequence during sexual reproduction in Angiosperms?
Answer and solution
Answer: (a) Egg → zygote → embryo → seed
Method. order of events after fertilization
Egg (fertilised) gives the zygote, the zygote divides to the embryo, and the ovule becomes the seed holding the embryo (NCERT C7-A45, C7-A48). So egg, zygote, embryo, seed.
22. NDA 2023 (II)
Which one of the following combinations of events represents the correct sequence during reproduction in flowering plants?
Answer and solution
Answer: (d) Egg → zygote; zygote → embryo; ovule → seed; ovary → fruit
Method. fates of floral parts in reproduction
Egg gives zygote (fertilisation); zygote gives embryo; ovule gives seed; ovary gives fruit (NCERT C7-A45, C7-A48). The others reverse one or more of these steps (ovule does not become fruit, embryo does not become egg, and so on).
23. NDA 2022 (II)
After fertilization, the fruit and the seed are produced by
Answer and solution
Answer: (b) ovary and ovule, respectively
Method. fate of floral parts after fertilization
After fertilization the ovary ripens into the fruit and the ovules become seeds (NCERT C7-A48; also NS11-A51 in Class 9).
24. NDA 2021 (I)
During seed germination, the part of the embryo which grows into root is
Answer and solution
Answer: (a) Radicle.
Method. parts of the embryo in a germinating seed
The radicle is the future root and the plumule the future shoot (NCERT C7-A89). The cotyledon is the food store. The epicotyl is the stem part above the cotyledons.
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