Plant Physiology: Questions and Answers!
Q. 1. How will you define diffusion?
Ans. The natural movement of molecules of a solute from regions of higher concentration to the regions of lower concentration is called diffusion.
Q. 2. Explain the phenomenon of osmosis.
Ans. The process of the movement of water across the semipermeable membrane from a hypotonic solution to a hypertonic solution is called osmosis.
Q. 3. Differentiate between the terms hypotonic and hypertonic.
Ans. Hypotonic means less concentrated whereas hypertonic means more concentrated.
Q. 4. What do you understand by semipermeable membrane?
Ans. A membrane, which allows some substances to pass through, but not the others, is called semipermeable membrane.
Q. 5. Explain the term osmotic pressure.
Ans. It is a pressure required to prevent the osmotic movement of pure water into a solution across a semipermeable membrane.
Q. 6. Explain the meaning of plasmolysis.
Ans. It is the shrinkage of the protoplasm of the cell away from its cellulose wall when placed in hypertonic solutions, mainly because of the osmotic withdrawal of water from its large central vacuole.
Q. 7. What do you mean by turgor?
Ans. Turgor is the tension on a cell wall because of the pressure of water inside the cell.
Q. 8. Explain the meaning of turgid.
Ans. Turgid is the state of a cell under which it can absorb no more water by osmosis.
Q. 9. What is the meaning of root pressure?
Ans. The pressure which is partly responsible for the upward movement of xylem sap is called root pressure.
Q. 10. What is a potometer?
Ans. It is an instrument used for measuring the transpiration rate.
Q. 11. Explain the meaning of transpiration.
Ans. Loss of water vapours by the land plants, mainly from their leaves, is called transpiration. Chiefly it takes place through stomata, and to a much lesser extent through the cuticle.
Q. 12. What it translocation?
Ans. Translocation is the movement of substance in the vascular system of the plant from one part to another.
Q. 13. What do you mean by active transport of substances?
Ans. It is the movement of substances across membranes, using energy.
Q. 14. Explain the meaning of photosynthesis.
Ans. Photosynthesis is the process under which green plants use energy from sunlight to produce carbohydrates from water and carbon dioxide.
The general equation for photosynthesis is:
CO2 + 4H2O (CH26) + 3H2O + O2
Q. 15. What is chloroplast?
Ans. Chloroplast is a green plastid which contains chlorophyll. Chloroplasts are the actual site for photosynthesis process. It remains surrounded by a double-membrane envelope which encloses grana and stroma.
Q. 16. What are grana?
Ans. Grana are the stacks of the flat vesicles or thylakoids present in the chloroplast. Light reactions of photosynthesis takes place in the grana.
Q. 17. Where does the dark reaction of photosynthesis take place?
Ans. Dark reaction takes place in stroma.
Q. 18. What is thylakoid?
Ans. Thylakoid is a flat vesicle in the grana of chloroplast.
Q. 19. When CO2 reacts with ribulose-diphosphate, how many molecules of PGA are formed?
Ans. Two molecules of PGA.
Q. 20. What is ribulose diphosphate?
Ans. This is the main compound involved in CO2 fixation in photosynthesis process. Also called RuDP this compound consists of a molecule of pentose sugar ribulose and two phosphate groups.
Q. 21. What do you mean by PGA?
Ans. PGA is the short form of phosphoglyceric acid. It is a compound with three carbon atoms. Reaction between CO2 and ribulose diphosphate first produces PGA.
Q. 22. Explain the meaning of C3 pathway.
Ans. It is the process of CO2 fixation by ribulose diphosphate to give rise to two molecules of PGA. Plants using this pathway are called C3 plants.
Q. 23. What are the other names of C3 pathway?
Ans. Calvin cycle and reductive pentose pathway.
Q. 24. C4 pathway is found in which category of plants?
Ans. This kind of CO2 fixation is found in tropical monocotyledons.
Q. 25. What happens in C4 pathway?
Ans. In C4 pathway CO2 is fixed by a three-carbon atom compound to produce a molecule with four carbon atoms.
Q. 26. What is CAM?
Ans. CAM stands for crassulacean acid metabolism. It is a kind of c02 fixation which is found in many succulent plants, e.g., members of Crassulaceae.
Q. 27. What comes under light reactions?
Ans. These are the reactions in which green pigments are used to trap light energy from sunlight. Light reactions result in the splitting of H2O molecules into hydrogen and oxygen, and in the production of NADPH2and ATP.
Q. 28. What is the role of photolysis of water in light reaction of photosynthesis?
Ans. Photolysis results in splitting of water molecules into hydrogen and oxygen.
Q. 29. What is the name of the reaction which involves the reduction of NADP into NADPH2 in the light reaction of photosynthesis?
Ans. Hill Reaction.
Q. 30. What are chlorophylls?
Ans. These are the magnesium-containing green pigments of the chloroplasts of plants. Chlorophylls trap light energy for photosynthesis.
Q. 31. What are the formulae of chlorophyll ‘a’ and chlorophyll ‘b’?
Ans. Chlorophyll ‘a’—C55H72O5N4Mg
Chlorophyll ‘b’ —C35H70O6N4Mg
Q. 32. What is plastocyanin?
Ans. It is a blue, copper-containing protein. It functions as an electron carrier in the light reaction of photosynthesis.
Q. 33. What is the formula of carotene?
Ans. C40H56
Q. 34. Explain the meaning of the word ‘wavelength’.
Ans. The length of a wave of light is called wavelength. Different colours and different energy levels are shown by different wavelengths.
Q. 35. The word NADP stands for what?
Ans. NADP stands for nicotinamide adenine dinucleotide phosphate.
Q. 36. Explain briefly the meaning of the word photophosphorylation.
Ans. Photophosphorylation is the part of the light reaction in which ADP is phosphorylated to ATP by using light energy.
Q. 37. What do you mean by glycolysis?
Ans. Glycolysis is the process of the anaerobic sequence of reactions in the glucose breakdown. It results in the formation of pyruvic acid.
Q. 38. What is the formula of pyruvic acid?
Ans. CH3COCOOH
Q. 39. What are the other names of Kreb’s cycle?
Ans. Citric acid cycle, Tricarboxylic acid cycle or TCA cycle.
Q. 40. Where does the Kreb’s cycle take place?
Ans. Kreb’s cycle takes place in the mitochondria.
Q. 41. What is NAD?
Ans. It is a hydrogen carrier in the Kreb’s cycle with its full name as nicotinamide adenine dinucleotide.
Q. 42. Give a precise definition of photorespiration.
Ans. It is a physiological process in which plants, in the presence of high oxygen concentration, light and low CO2 concentration, take up oxygen and give off CO2, because of the oxidation of organic compounds produced by CO2fixatiort.
Q. 43. What are the full forms of ADP and ATP?
Ans. ADP stands for adenosine diphosphate whereas ATP stands for adenosine triphosphate.
Q. 44. What do you understand by phosphorylation?
Ans. Phosphorylation is a reaction in which a phosphate group is added to a molecule, e.g., phosphorylation of ADP to produce ATP.
Q. 45. What are trace elements?
Ans. The elements required by the plants in very small amounts are called trace elements, e.g., molybdenum.
Q. 46. Explain the meaning of the terms hydathode and guttation.
Ans. Hydathode is a water-exuding gland found on the leaves of some plants. Guttation is the process of water exudation through the hydathodes.
Q. 47. What are hormones and their main groups?
Ans. Hormones are the substances which control the growth and development in the plants and are found in very small amounts. Plant hormones fall in five main groups, viz., auxins, gibberellins, cytokinins, abscisic acid and ethene or ethylene.
Q. 48. What is ethylene or ethene?
Ans. It is a simple plant hormone (C2H4) which affects abscission, root growth inhibition, tropisms and fruit ripening.
Q. 49. Define a florigen.
Ans. It is a plant hormone involved in the production of flowers in the plants.
Q. 50. Differentiate between vernalization and senescence.
Ans. Vernalization is the phenomenon of flowering due to the treatment with low temperatures. Senescence is the process of growing old before the death.