Important Points 

11. The main site of respiration in plants is the mitochondria.
12. Dark respiration occurs both in light and darkness.
13. The process of oxidative phosphorylation occurs in the inner mitochondrial membrane.
14. Kranz anatomy is a characteristic feature of C4 plants.
15. The bundle sheath cells are large and contain chloroplasts in C4 plants.
16. C4 plants have higher water use efficiency than C3 plants.
17. Rice and wheat are examples of C3 plants.
18. Maize, sugarcane, and sorghum are examples of C4 plants.
19. The compensation point is the light intensity at which photosynthesis equals respiration.
20. Transpiration pull plays a major role in water transport in tall trees.
21. Hydathodes are responsible for guttation.
22. Guttation occurs during night or early morning.
23. Wilting is the loss of turgidity due to excessive transpiration.
24. Osmosis is the movement of water through a semi-permeable membrane.
25. Plasmolysis is the shrinkage of cytoplasm from the cell wall due to water loss.
26. Deplasmolysis is the re-entry of water into the plasmolysed cell.
27. Transpiration ratio is the amount of water transpired per unit of dry matter produced.
28. Water potential is always negative in plant cells.
29. Turgor pressure helps in cell enlargement.
30. The symplast pathway involves movement through cytoplasm.
31. The apoplast pathway involves movement through cell walls and intercellular spaces.
32. Casparian strip is present in the endodermis.
33. Cohesion is the attraction between water molecules.
34. Adhesion is the attraction between water and the walls of xylem vessels.
35. Water potential gradient drives water movement in plants.
36. Stomatal frequency is the number of stomata per unit area.
37. Sunken stomata help in reducing water loss.
38. Osmotic potential becomes more negative as solute concentration increases.
39. Relative water content (RWC) indicates the plant’s hydration status.
40. Antitranspirants are chemicals used to reduce water loss.
41. Phenol and silicone oils are used as film-forming antitranspirants.
42. Kaolin acts as a reflectant antitranspirant.
43. Abscisic acid acts as a metabolic antitranspirant.
44. Cytokinins delay leaf senescence by mobilizing nutrients.
45. Ethylene accelerates fruit ripening by increasing respiration rate.
46. Respiratory climacteric refers to a sudden increase in respiration during fruit ripening.
47. Banana and tomato are climacteric fruits.
48. Citrus and grapes are non-climacteric fruits.
49. Light saturation point is higher in C4 plants than in C3 plants.
50. Light compensation point is lower in shade-loving plants.
51. Photooxidation of chlorophyll is caused by intense light.
52. Chlorosis is caused by deficiency of nitrogen, iron, magnesium, or sulfur.
53. Necrosis refers to death of tissue, usually due to potassium or calcium deficiency.
54. Leaf curling is caused by boron deficiency.
55. Brown heart of turnip is due to boron deficiency.
56. White bud of maize is caused by zinc deficiency.
57. Little leaf of cotton is due to zinc deficiency.
58. Khaira disease of rice is due to zinc deficiency.
59. Whiptail disease of cauliflower occurs due to molybdenum deficiency.
60. Dieback of citrus is caused by copper deficiency.

Plant Growth and Development

1. Plant growth is an irreversible increase in size, weight, and volume.
2. Meristematic tissues are responsible for growth and cell division.
3. Apical meristem causes primary growth.
4. Lateral meristem causes secondary growth.
5. Intercalary meristem is present at the base of leaves or internodes.
6. Growth curve of a plant is typically sigmoid (S-shaped).
7. The lag phase is the initial slow growth phase.
8. The log phase is the period of maximum growth rate.
9. The stationary phase is when growth becomes constant.
10. The final size of an organ is genetically determined.
11. Differentiation is the process by which cells become specialized.
12. Dedifferentiation is the return of specialized cells to meristematic state.
13. Redifferentiation is when dedifferentiated cells again become specialized.
14. Development includes both growth and differentiation.
15. Quantitative growth refers to increase in size, while qualitative growth refers to improvement in function.
16. Plant growth regulators (PGRs) are organic substances that influence physiological processes.
17. The five major PGRs are Auxins, Gibberellins, Cytokinins, Ethylene, and Abscisic acid.
18. Auxins were first discovered by W. Went (1928).
19. The first natural auxin discovered was Indole-3-acetic acid (IAA).
20. Auxins promote cell elongation, root initiation, and apical dominance.

Plant Growth Regulators

1. IAA, IBA, NAA, and 2,4-D are common synthetic auxins.
2. 2,4-D is widely used as a selective weed killer.
3. Apical dominance is mainly regulated by auxins.
4. Gibberellins promote stem elongation and seed germination.
5. The first gibberellin was isolated from the fungus Gibberella fujikuroi.
6. The disease caused by Gibberella fujikuroi in rice is Bakanae (foolish seedling).
7. Gibberellins can break seed and bud dormancy.
8. GA3 is the most commonly used gibberellin in agriculture.
9. Cytokinins promote cell division and delay senescence.
10. The first cytokinin discovered was kinetin.
11. Natural cytokinin present in plants is zeatin.
12. Cytokinins and auxins together control organ formation (morphogenesis) in tissue culture.
13. High auxin:cytokinin ratio promotes root formation.
14. Low auxin:cytokinin ratio promotes shoot formation.
15. Ethylene is the only gaseous hormone.
16. Ethylene promotes fruit ripening and leaf abscission.
17. Ethephon (2-chloroethyl phosphonic acid) is a commercial source of ethylene.
18. Abscisic acid (ABA) is called the stress hormone or dormin.
19. ABA induces stomatal closure under water stress.
20. ABA also induces seed dormancy.