Yield Physiology

1. Harvest Index (HI) = Economic yield / Biological yield × 100.
2. Typical HI for cereals: 40–50%.
3. Source – photosynthetic tissues; Sink – storage organs (grain, fruit).
4. Remobilization – movement of stored carbohydrates to developing organs.
5. Lodging occurs due to excessive nitrogen or weak stem.
6. Senescence – natural aging leading to death of organs.
7. Dry Matter Partitioning – distribution of assimilates to various plant parts.
8. Translocation of assimilates occurs through
9. Light Saturation Point – intensity beyond which photosynthesis doesn’t increase.
10. Law of Minimum proposed by Liebig (1840).

Important Scientists and Theories

1. Blackman (1905) – Law of Limiting Factors in photosynthesis.
2. Calvin (1957) – Discovered the Calvin Cycle.
3. Hatch & Slack (1966) – discovered C₄ pathway.
4. Krasnovsky (1948) – discovered photosynthetic phosphorylation.
5. Priestley (1771) – discovered oxygen in photosynthesis.
6. Ingenhousz (1779) – showed that sunlight is essential for photosynthesis.
7. Moll (1851) – discovered stomatal transpiration.
8. Arnon (1954) – discovered cyclic and non-cyclic photophosphorylation.
9. Went (1928) – discovered auxin (IAA).
10. Skoog and Miller (1957) – discovered

Seed Physiology

1. Seed dormancy – inability of viable seed to germinate under favorable conditions.
2. Scarification – mechanical/chemical treatment to break seed coat dormancy.
3. Stratification – chilling treatment to break physiological dormancy.
4. Viability – ability of a seed to germinate.
5. Germination starts with imbibition of water.
6. Respiration rate increases during germination.
7. Vigour index = Germination (%) × Seedling length.
8. Tetrazolium test measures seed viability.
9. Moisture content for safe storage of most seeds – 8–10%.
10. Orthodox seeds tolerate drying; Recalcitrant seeds cannot be dried (e.g., Coconut).

Other Important Points

11. Photosynthesis was discovered by Priestley.
12. The Calvin cycle occurs in the stroma of chloroplast.
13. The light reaction of photosynthesis takes place in the grana.
14. RuBisCO is the most abundant enzyme on Earth.
15. The first product of photosynthesis in C3 plants is 3-phosphoglyceric acid (PGA).
16. The first stable product in C4 plants is oxaloacetic acid (OAA).
17. CAM plants fix CO₂ during the night.
18. Photorespiration occurs only in the presence of light.
19. The process of conversion of light energy into chemical energy is called photosynthesis.
20. The optimum temperature for photosynthesis in tropical crops is 25–35°C
21. The process of loss of water in the form of vapour is called transpiration.
22. The instrument used to measure transpiration is potometer.
23. The opening and closing of stomata are regulated by guard cells.
24. The turgidity of guard cells is controlled by potassium ions (K⁺).
25. Xylem transports water, while phloem transports food.
26. The translocation of food in plants occurs through phloem by mass flow hypothesis.
27. Nitrate reductase enzyme is responsible for the reduction of nitrate to nitrite.
28. Chlorophyll contains magnesium at its center.
29. The deficiency of iron causes chlorosis in young leaves.
30. Phototropism is the movement of plants towards light.
31. The movement of water from roots to leaves is called ascent of sap.
32. Cohesion-tension theory explains water movement in plants.
33. The pressure developed in xylem due to water absorption is root pressure.
34. The point at which a leaf loses its turgidity is permanent wilting point.
35. Stomatal transpiration accounts for about 90% of total water loss in plants.
36. The process by which seeds absorb water is imbibition.
37. Auxins promote cell elongation.
38. Gibberellins are responsible for stem elongation and seed germination.
39. Cytokinins promote cell division.
40. Abscisic acid (ABA) induces dormancy and abscission.
41. The hormone responsible for fruit ripening is ethylene.
42. Bolting in onions is promoted by gibberellins.
43. Apical dominance is controlled by auxins.
44. Photoperiodism is the response of plants to the length of day and night.
45. Vernalization is the process of inducing flowering by low temperature.
46. C3 pathway was discovered by Calvin and Benson.
47. C4 pathway was discovered by Hatch and Slack.
48. CAM pathway is found in succulent plants.
49. The energy currency of the cell is ATP.
50. Respiration occurs in mitochondria.
51. Glycolysis occurs in the cytoplasm.
52. The end product of aerobic respiration is CO₂ and H₂O.
53. The end product of anaerobic respiration is alcohol or lactic acid.
54. The Q. (Respiratory Quotient) for carbohydrates is 1.
55. The Q. for fats is less than 1.
56. The Q. for organic acids is greater than 1.
57. The most energy-efficient substrate for respiration is glucose.
58. Senescence is the natural aging process in plants.
59. The hormone delaying senescence is cytokinin.
60. The process of shedding leaves and fruits is called abscission.