The document summarizes photosynthesis in plants. It describes how plants perform autotrophic nutrition by using carbon dioxide, water, and sunlight to produce oxygen and glucose through the processes of light and dark reactions in the chloroplasts. Photosynthesis occurs primarily in leaves, which have adaptations like thinness, large surface area, and stomata to facilitate gas exchange and maximize light absorption for efficient photosynthesis.

1. Nutrition in Plants

2. How does trees on the fertile plain obtain their nutrients ? Or the algae in the sea ? Or the cacti in the desserts ?

3. Review Question Which mode of nutrition do the green plants carry out? A. Autotrophic nutrition B. Heterotrophic nutrition

4. Sorry! You’re wrong! Heterotrophic nutrition is the mode of nutrition in which organisms have to depend on other organisms or dead organic matters as their food sources. Green plants, however, can make organic food by themselves using simple inorganic substances.

5. Very Good! Autotrophic nutrition is the mode of nutrition in which organisms can make organic food by themselves using simple inorganic substances . The process by which the green plants obtain nutrients is called : Photosynthesis

6. Nature of photosynthesis Takes place in Chloroplast Necessary factors : Carbon dioxide Water Sunlight Chlorophyll

7. Route of Carbon Dioxide for Photosynthesis

8. CO 2 Stoma Air Space Spongy Mesophyll Cell Chloroplast

9. CO 2 Chloroplast Palisade Mesophyll Cell Stoma Air Space

10. Light energy is trapped by chlorophyll in chloroplast Light energy absorbed by chlorophyll splits water molecules into hydrogen and oxygen Oxygen is released as a gas through stoma to outside Hydrogen is fed into dark reaction Light reaction

11. 6 blue red % of light absorbed by chlorophyll green

12. Oxygen is produce as the by-product of photosynthesis.

13. Dark reaction No light is required ; can take place either in light or darkness Hydrogen produced in light reaction combines with CO 2 to form carbohydrates Water is formed as a by-product

14. Dark Reaction H Summary of Photosynthesis Water Oxygen Glucose ( C 6 H 12 O 6 ) Light Reaction 6 CO 2 + 6 H 2 0 C 6 H 12 O 6 + 6 O 2 Light Carbon Dioxide

15. Fate of carbohydrate products in the plant

16. carbohydrates (e.g. glucose) carbon dioxide and water release energy by respiration photosynthesis

17. convert into starch for storage because glucose is not a very good storage molecule carbohydrates (e.g. glucose) carbon dioxide and water photosynthesis

18. change into sucrose and is transported to other parts through phloem carbohydrates (e.g. glucose) carbon dioxide and water photosynthesis

19. carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) combine to form fats and oils to form cell membranes and as a food store fatty acids glycerol

20. carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) mineral salts from soil (e.g. NO 3 - , SO 4 2- ) amino acids join together to become protein molecules

21. Experiments on photosynthesis

22. Destarching Reason: To avoid any existing starch in the leaves interfering with the result , and to show that any starch found after the experiment is produced during the period of investigation Method: By placing the plant in dark for at least 48 hours

23. To test a leaf for the presence of Starch Investigation 8.1

24. Why is the leaf first boiled in water ? Ans: Because the process can soften the leaf, break down the cuticle and kill the leaf. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

25. Why is the leaf then boiled in alcohol ? Ans: To decolourize the leaf (to remove chlorophyll). boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

26. Why is it important to turn off the Bunsen burner when you are heating the alcohol ? Ans: Because alcohol catches fire easily. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

27. Why is the leaf put in hot water after being boiled in alcohol ? Ans: Since the leaf becomes brittle after boiling in alcohol, so dipping it into hot water enables it to be softened. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

28. What colour change can be observed if starch is present ? Ans: The leaf becomes blue-black when iodine solution is added to it. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

29. To show that Chlorophyll is necessary for Photosynthesis Investigation 8.3

30. Which part of the leaf turns blue-black when treated with iodine solution ? Ans: Only the green part. green part purple part

31. Is chlorophyll necessary for photosynthesis ? Ans: Yes. green part purple part

32. What is the control in this experiment ? Ans: The green part of the leaf acts as the control. green part purple part

33. To show that Carbon Dioxide is necessary for Photosynthesis Investigation 8.4

34. Why is potassium hydroxide solution put in one of the flasks ? Ans: To absorb all the carbon dioxide in flask B. sunlight B A water potassium hydroxide solution

35. What happens to each leaf after testing the presence of starch at the end of the experiment ? Ans: The leaf in flask A changes to blue-black while the leaf in flask B stains brown. sunlight B A water potassium hydroxide solution

36. What do your results suggest about the relationship between carbon dioxide and photosynthesis ? Ans: Carbon dioxide is necessary for photosynthesis. sunlight B A water potassium hydroxide solution

37. Factors affecting the rate of photosynthesis

38.  Light intensity  Rate of Photosynthesis Light Intensity

39.  Carbon dioxide concentration  Rate of Photosynthesis Carbon Dioxide Concentration

40.  Temperature  Rate of Photosynthesis Temperature Temperature > 40 ℃ Rate  & Stop soon

41. If no water, stomata close no gaseous exchange photosynthesis ceases Water Supply

42. Why is Photosynthesis important ? Green plants: the only organisms capable of trapping light to manufacture food from simple inorganic substances

43. Why is Photosynthesis important ? Green plants(producers) starts the food chain & provide food for other organisms

44. Why is Photosynthesis important ? Atmospheric carbon dioxide is absorbed & oxygen is released into the atmosphere which maintains the composition of the atmosphere constant

45. Parts of plant where photosynthesis takes place Mainly in the leaf because it contains a lot of chloroplasts it is well adapted for performing photosynthesis

46. Internal Structure of Leaf

47. cuticle upper epidermis palisade mesophyll spongy mesophyll intercellular space (air space) guard cell lower epidermis cuticle stoma chloroplasts

48. Cross-section of a leaf of dicotyledon

49. upper epidermis protect internal tissues from mechanical damage and bacterial & fungal invasion

50. Cuticle a waxy layer prevent water loss from the leaf surface protect the leaf

51. mesophyll

52. palisade mesophyll (layer) columnar cells closely packed together  absorb light more efficiently contains many chloroplasts

53. spongy mesophyll (layer) irregular cells loosely packed together to leave numerous large air spaces  allow rapid diffusion of gases throughout the leaf some (fewer than palisade mesophyll) chloroplasts for photosynthesis

54. lower epidermis same as upper epidermis except the cuticle is thinner

55. stoma (stomata) opening which allows gases to pass through it to go into or out of the leaf

56. guard cells control the size of stoma

57. Stoma stoma Guard cells thinner outer wall thicker inner wall

58. vascular bundle ( vein )

59. Internal Structure of Leaf xylem phloem

60. xylem to transport water and mineral salts towards the leaf for mechanical support

61. phloem to transport organic substances ( food/sugar/ glucose/ sucrose ) away from the leaf

62. Adaptation of leaf to photosynthesis

63. The leaf is thin decrease diffusion distance for gases & light The leaf is broad & flattened increase surface area to absorb more sunlight

64. Cuticle exists in upper epidermis and is transparent Allows most light to pass into photosynthetic mesophyll tissues

65. Palisade mesophyll cells are closely packed and contain many chloroplasts To carry out photosynthesis more efficiently

66. Spongy mesophyll cells are loosely packed with numerous large air spaces To allow rapid diffusion of gases throughout the leaf

67. Numerous stoma ta on lower epidermis To allow rapid gaseous exchange with the atmosphere

68. Extensive vein system Allow sufficient water to reach the cells in the leaf To carry food away to other parts of the plant

69. Mineral requirements in plants In order to synthesize amino acids, nitrate ions which must be taken into the plant from the soil through the root Other minerals are also necessary to maintain the life of the plant (N, Mg, P, K, S, etc)

70. The importance of nitrogen For synthesis of proteins, chlorophyll, etc Taken in form of nitrate ions Deficiency symptoms: Little growth ( - no protein made) Yellowing of leaves ( - no chlorophyll made)

71. The importance of magnesium Essential component of chlorophyll Deficiency symptoms: Yellowing of leaves (no chlorophyll made) Poor growth (no food manufactured because of lack of chlorophyll)

72. Use of fertilizers in agriculture Continuous harvesting crops removes valuable mineral salts from soil  Fertilizers are added to replace such loss Two kinds of fertilizers: Natural fertilizers Chemical fertilizers

73. Natural fertilizers From manure Organic compounds in it are decomposed by the bacteria in soil to form mineral salts

74. Chemical fertilizers Mainly nitrogenous and phosphorous compounds manufactured artificially

75. Comparison between natural and chemical fertilizers Natural fertilizers Chemical fertilizers Contain humus which can improve soil texture No humus so cannot improve soil texture Less soluble in water so less likely to be washed away Very soluble in water so more likely to be washed away

76. Comparison between natural and chemical fertilizers Natural fertilizers Chemical fertilizers Less soluble in water so more difficult to be absorbed Very soluble in water so easier to be absorbed More readily to be used by the plants Time is needed for the decomposition to complete before nutrients are available to plants Very expensive Much cheaper

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