Plant Physiology & Biochemistry MCQs BSc Set-3


1.The hormone produced during adverse environmental conditions is

(a) Benzyl aminopurine
(b) Dichlorophenoxyacetic acid
(c) Ethylene
(d) Abscisic acid.

Answer:(d) Abscisic acid.

2. The regulator which retards ageing/senescence of plant parts is

(a) Cytokinin
(b) Auxin
(c) Gibberellin
(d) Abscisic acid.

Answer:(a) Cytokinin

3. Removal of apical bud results in

(a) Formation of new apical bud
(b) Elongation of main stem
(c) Death of plant
(d) Formation of lateral branching.

Answer:(d) Formation of lateral branching.

4. Translocation of carbohydrate nutrients usually occurs in the form of

(a) Glucose
(b) Maltose
(c) Starch
(d) Sucrose.

Answer:(d) Sucrose.

5. Which one is a C4-plant?

(a) Papaya
(b) Pea
(c) Potato
(d) Maize/corn

Answer:(d) Maize/corn

6. The carbon dioxide acceptor in Calvin cycle/ C3-plants is

(a) Phospho-enol pyruvate (PEP)
(b) Ribulose 1, 5-diphosphate (RuBP)
(c) Phosphoglyceric acid (PGA)
(d) Ribulose monophosphate (RMP).

Answer:(b) Ribulose 1, 5-Diphosphate (RuBP)

7. Maximum solar energy is trapped by

(a) Planting trees
(b) Cultivating crops
(c) Growing algae in tanks
(d) Growing grasses.

Answer:(c) Growing algae in tanks

8. A photosynthesis plant is releasing lsO more than normal. The plant must have been supplied with

(a) O3
(b) H20 with 180O
(c) CO2 with 15O
(d) C6H12O6 with 18O.

Answer:(b) H20 with 180O

9. Plants, but not animals, can convert fatty acids to sugars by a series of reactions called

(a) Photosynthesis
(b) Kreb’s cycle
(c) Glycolysis
(d) Glyoxylate cycle.

Answer:(d) Glyoxylate cycle.

10. During light reaction of photosynthesis, which of the following phenomena is observed during cyclic phosphorylation as well as non-cyclic phosphorylation?

(a) Release of O2
(b) Formation of ATP
(c) Formation of NADPH
(d) Involvement of PS I and PS II pigment systems.

Answer:(b) Formation of ATP

11. Which of the following pigments acts as a reaction- centre during photosynthesis?

(a) Carotene
(b) Phytochrome
(c) P700
(d) Cytochrome.

Answer:(c) P700

12. If the growing plant is decapitated, then

(a) Its growth stops
(b) Leaves become yellow and fall down
(c) Axillary buds are inactivated
(d) Axillary buds are activated.

Answer:(d) Axillary buds are activated.

13. The movement of auxin is largely

(a) Centripetal
(b) Basipetal
(c) Acropetal
(d) Both ‘a’ and ‘c’.

Answer:(b) Basipetal

14. The 1992 Nobel Prize for medicine was awarded to Edmond H. Fischer and Edwin J.Krebs for their work concerning

(a) Reversible protein phosphorylation as a biological regulation mechanism
(b) Isolation of the gene for a human disease
(c) Human genome project
(d) Drug designing involving inhibition of DNA synthesis of the pathogen.

Answer:(a) Reversible protein phosphorylation as a biological regulation mechanism

15. The closure of lid pitcher in pitcher plant,is due to

(a) Paratonic movement
(b) Autonomous movement
(c) Turgor movement
(d) Tropic movement.

Answer:(a) Paratonic movement

16. The movement of water, from one cell of cortex to adjacent one in roots, is due to

(a) Accumulation of inorganic salts in the cells
(b) Accumulation of organic compounds in the cells
(c) Water potential gradient
(d) Chemical potential gradient.

Answer:(c) Water potential gradient

17. The C02 fixation during C4 pathway occurs in the chloroplast of

(a) Guard cells
(b) Bundle sheath cells
(c) Mesophyll cells
(d) Spongy parenchyma.

Answer:(c) Mesophyll cells

18. The twinning of tendrils around a support is a good example of

(a) Phototropism
(b) Chemotropism
(c) Nastic movements
(d) Thigmotropism.

Answer:(d) Thigmotropism.

19. The primary acceptor, during C02 fixation in C3 paints, is

(a) Phosphoenolpyruvate (PEP)
(b) Ribulose 1, 5-Diphosphate (RuDP)
(c) Phosphoglyceric acid (PGA)
(d) Ribulose monophosphate (RMP).

Answer:(b) Ribulose 1, 5-Diphosphate (RuDP)

20. Which of the following elements plays an important role in biological nitrogen fixation?

(a) Copper
(b) Molybdenum
(c) Zinc
(d) Manganese.

Answer:(b) Molybdenum

21. In C4 plants, CO2 fixation is done by

(a) Sclerenchyma
(b) Chlorenchyma and hypodermis
(c) Mesophyll cells
(d) Guard cells.

Answer:(c) Mesophyll cells

22. Which one of the following elements is almost non essential for plants?

(a) Zn
(b) Na
(c) Ca
(d) Mo

Answer:(b) Na

23. In C4 plants, CO2 combines with

(a) Phosphoenol pyruvate
(b) Phosphoglyceraldehyde
(c) Phosphoglyceric acid
(d) Ribulose diphosphate.

Answer:(a) Phosphoenol pyruvate

24. When water enters in roots due to diffusion, is termed as

(a) Osmosis
(b) Passive absorption
(c) Endocytosis
(d) Active absorption.

Answer:(b) Passive absorption

25. Photorespiration is favoured by

(a) High temperature and low O2
(b) High humidity and temperature
(c) High O2 and low CO2
(d) High CO2 and low O2.

Answer:(c) High O2 and low CO2

26. What will be the number of Calvin cycles to generate one molecule of hexose?

(a) 8
(b) 9
(c) 4
(d) 6

Answer:(d) 6

27. ‘The law of limiting factors’ was proposed by

(a) Leibig
(b) Hatch and Slack
(c) Blackman
(d) Arnon.

Answer:(c) Blackman

28. The correct sequence of electron acceptor in ATP synthesis is

(a) Cyt. b, c, a3, a
(b) Cyt. c, b, a, a3
(c) Cyt. o, a, b, c
(d) Cyt. b, c, a, a3.

Answer:(d) Cyt. b, c, a, a3.

29. Bidirectional translocation of solutes takes place in

(a) Parenchyma
(b) Cambium
(c) Xylem
(d) Phloem.

Answer:(d) Phloem.

30. Gibberellic acid induces flower

(a) In short day plants under long day conditions
(b) In day-neutral plants under dark conditions
(c) In some gymnosperm plants only
(d) In long day plants under short day conditions.

Answer:(d) In long day plants under short day conditions.

31. If a tree flowers thrice in a year (Oct., Jan. and July) in Northern India, it is said to be

(a) Photo and thermo-insensitive
(b) Photo and thermo-sensitive
(c) Photosensitive but thermo-insensitive
(d) Thermosensitive but photo-insensitive.

Answer:(a) Photo and thermo-insensitive

32. What will be the effect on phytochrome in a plant subjected to continuous red light?

(a) Phytochrome synthesis will increase
(b) Level of phytochrome will decrease
(c) Phytochrome will be destroyed
(d) First (b) then (a)

Answer:(d) First (b) then (a)

33. With an increase in the turgidity of a cell, the wall pressure will be

(a) Fluctuate
(b) Remain unchanged
(c) Increase
(d) Decrease.

Answer:(c) Increase

34. Which of the following is not caused by deficiency of mineral nutrition?

(a) Etiolation
(b) Shortening of internode
(c) Necrosis
(d) Chlorosis.

Answer:(a) Etiolation

35. When a cell is fully turgid, which of the following will be zero?

(a) Turgor pressure
(b) Water potential
(c) Wall pressure
(d) Osmotic pressure.

Answer:(b) Water potential

36. NADPH2 is generated through

(a) Photosystem II
(b) Anaerobic respiration
(c) Glycolysis
(d) Photosystem I

Answer:(d) Photosystem I

37. A pigment which absorbs red and far-red light is

(a) Cytochrome
(b) Xanthophyll
(c) Phytochrome
(d) Carotene

Answer:(c) Phytochrome

38. The core metal of chlorophyll is

(a) Ni
(b) Cu
(c) Fe
(d) Mg

Answer:(d) Mg

39. Chlorophyll-a molecule at its carbon atom 3 of the pyrrole ring II has one of the following

(a) Carboxylic group
(b) Magnesium
(c) Aldehyde group
(d) Methyl group

Answer:(d) Methyl group

40. Which one among the following chemicals is used for causing defoliation of forest trees?

(a) Maleic hydrazide
(b) 2, 4-D
(c) Amo-1618
(d) Phosphon D.

Answer:(b) 2, 4-D

41. Phytochrome becomes active in

(a) Red light
(b) Green light 
(c) Blue light
(d) None of these

Answer:(d) None of these

42. The water potential and osmotic potential of pure

(a) 100 and 200
(b) Zero and 100
(c) 100 and zero
(d) Zero and zero

Answer:(d) Zero and zero

43. Which combination of gases is suitable for fruit ripening?

(a) 80 % CH4 and 20% CO2
(b) 80% CO2 and 20% O2
(c) 80% C2H4 and 20% CO2
(d) 80% CO2 and 20% CH2.

Answer(c) 80% C2H4 and 20% CO2

44. Which one of the following statements about cytochrome P450 is wrong?

(a) It is a coloured cell
(b) It is an enzyme involved in oxidation reactions
(c) It has an important role in metabolism
(d) It contains iron

Answer:(a) It is a coloured cell

45. The response of different organisms to the environmental rhythms of light and darkness is called

(a) Vernalization
(b) Photoperiodism
(c) Phototaxis
(d) Phototropism

Answer:(b) Photoperiodism

46. A plant hormone used for inducing morphogenesis in plant tissue culture is

(a) Cytokinins
(b) Ethylene
(c) Abscisic acid
(d) Gibberellins.

Answer:(a) Cytokinins

47. The closing and opening of the leaves of Mimosa pitdica is due to

(a) Seismonastic movement
(b) Chemonastic movement
(c) Thermonastic movement
(d) Hydrotropic movement.

Answer:(a) Seismonastic movement

48. The rate of photosynthesis is higher in

(a) Very high light
(b) Continuous light
(c) Red light
(d) Green light.

Answer: (c) Red light

49. ABA is involved in

(a) Hoot elongation
(b) Increased cell division
(c) Dormancy of seeds
(d) Root elongation.

Answer:(c) Dormancy of seeds

50. In soil, water available for plants is

(a) Gravitational water
(b) Chemically bound water
(c) Capillary water
(d) Hygroscopic water.

Answer:(c) Capillary water