2. YUMMY!!! Sigh, I wish its time for dinner already. I am so hungry! Hmmm, I wonder what we are having tonight!?

3. WOW!!! What a pretty flower!!!!!

4. Hey! I wonder if plants need to eat too!? If they do, then how do they get their food?

5. Of course we eat!!! And we are able to make our own food. That is why we are called AUTOTROPHS! Hmmm, I thought you learned all about this already!!! Do you remember how we can make our own food???

6. Things needed: LightLight Carbon dioxideCarbon dioxide WaterWater ChlorophyllChlorophyll Things produced: Carbohydrates (which can be used to form fats and proteins)Carbohydrates (which can be used to form fats and proteins) OxygenOxygen

7. Photosynthesis As one can see, plants need to obtain carbon dioxide in order to carry out photosynthesisAs one can see, plants need to obtain carbon dioxide in order to carry out photosynthesis They also release oxygen as a by-productThey also release oxygen as a by-product The process by which plants exchange oxygen and carbon dioxide is calledThe process by which plants exchange oxygen and carbon dioxide is called ___________ ___________ gas exchange

8. Gas Exchange Plants exchange gases by diffusionPlants exchange gases by diffusion Where does gas exchange occur in plants?Where does gas exchange occur in plants?

9. Internal Structure of Leaf

10. Gas Exchange Gas exchange mainly occurs in the leavesGas exchange mainly occurs in the leaves How do gases diffuse into and out of the leaves?How do gases diffuse into and out of the leaves?

12. Stomata

13. Stomata

14. Gas Exchange Gas exchange can also take place in the stems and rootsGas exchange can also take place in the stems and roots Herbaceous plants – diffusion through stomata on stem surfaceHerbaceous plants – diffusion through stomata on stem surface Woody plants - stomata when youngWoody plants - stomata when young - lenticels when matured - lenticels when matured

15. Lenticels Gases cannot penetrate the protective cork layerGases cannot penetrate the protective cork layer Lenticels are loosely-packed masses of cells in the bark of a woody plant, visible on the surface of a stem as raised spots, through which gas exchange occursLenticels are loosely-packed masses of cells in the bark of a woody plant, visible on the surface of a stem as raised spots, through which gas exchange occurs

16. Lenticels

17. Lenticels

18. Gas Exchange in Roots The epidermis is usually just one cell thick. Root epidermal cells lack a thick cuticle which would interfere with water uptake. Moreover, there is no stomata present as the cell membrane is very thin and therefore gases can directly diffuse into and out of the cellsThe epidermis is usually just one cell thick. Root epidermal cells lack a thick cuticle which would interfere with water uptake. Moreover, there is no stomata present as the cell membrane is very thin and therefore gases can directly diffuse into and out of the cells

19. Adaptation of Leaves to Photosynthesis

20. The leaf is thin Decreases diffusion distance for gases Adaptation of Leaves

21. Numerous stomata on lower epidermis Allows rapid gaseous exchange with the atmosphere Adaptation of Leaves

22. Guard cells control the size of stomata In presence of light, stomata open widely to allow the diffusion of carbon dioxide and oxygen Adaptation of Leaves

23. Guard Cells When turgor develops within the two guard cells, the outer walls bulge out and force the inner walls into a crescent shape. This opens the stomata. When the guard cells lose turgor, the elastic inner walls regain their original shape and the stomata closesWhen turgor develops within the two guard cells, the outer walls bulge out and force the inner walls into a crescent shape. This opens the stomata. When the guard cells lose turgor, the elastic inner walls regain their original shape and the stomata closes

24. Spongy mesophyll cells are loosely packed with numerous large air spaces Allows rapid diffusion and free circulation of gases throughout the leaf Adaptation of Leaves

25. Most cells in the leaves are surrounded by a layer of water Allows gases to dissolve and diffuse into and out of the cells

26. Gas Exchange CarbonDioxide Oxygen Photosynthesis Oxygen CarbonDioxide Respiration

27. What will be the net gas exchange between the leaf and its surrounding air?

28. Rate of Gas Exchange The rate of gas exchange is different throughout the day due to a change in light intensity

29. What is going on here?

30. Light Intensity Night – plants carry out RESPIRATION and release CARBON DIOXIDENight – plants carry out RESPIRATION and release CARBON DIOXIDE

31. Light Intensity

32. Night – plants carry out RESPIRATION and release CARBON DIOXIDENight – plants carry out RESPIRATION and release CARBON DIOXIDE Early morning – PHOTOSYNTHESIS begins to take place as light intensity increasesEarly morning – PHOTOSYNTHESIS begins to take place as light intensity increases Rate of photosynthesis < Rate of respiration Rate of photosynthesis < Rate of respiration Net release of CARBON DIOXIDE Net release of CARBON DIOXIDE

33. Light Intensity

34. Around 6:00 a.m. – light intensity increases even moreAround 6:00 a.m. – light intensity increases even more Rate of photosynthesis = Rate of respiration Rate of photosynthesis = Rate of respiration Release of CO 2 = Uptake of CO 2 Release of CO 2 = Uptake of CO 2 That is, there is NO net gas exchange That is, there is NO net gas exchange This is referred to as the COMPENSATION POINT This is referred to as the COMPENSATION POINT

35. Light Intensity

36. Afternoon – light intensity further increasesAfternoon – light intensity further increases Rate of photosynthesis > Rate of respiration Rate of photosynthesis > Rate of respiration Net uptake of CARBON DIOXIDE Net uptake of CARBON DIOXIDE Net uptake of carbon dioxide reaches a maximum in early afternoon Net uptake of carbon dioxide reaches a maximum in early afternoon

37. Light Intensity

38. Evening – light intensity begins to decreaseEvening – light intensity begins to decrease At a certain time period, there will again be a At a certain time period, there will again be a net release of CARBON DIOXIDE when plants net release of CARBON DIOXIDE when plants only carry out RESPIRATION at night only carry out RESPIRATION at night

39. Light Intensity

40. Similarly, we can study the relationship between light intensity and the exchange of OXYGEN

41. Critical Thinking 8.1 (p. 11) Question 1.Does a plant release or absorb oxygen at night? Ans: Ans: A plant absorbs oxygen at night

42. Critical Thinking 8.1 (p. 11) Question 2.When the light intensity gradually increases in the morning, will there be any changes in the exchange of oxygen? Why? Ans: The rate of oxygen uptake would gradually decrease and the rate of oxygen release would gradually increase. It is because photosynthesis begins to occur when light intensity gradually increases in the morning

43. Questions 3.Why is there a compensation point? 4.What will happen to the exchange of oxygen when the light intensity further increases? Ans: Compensation point refers to the light intensity at which there is no net gas exchange Critical Thinking 8.1 (p. 11) Ans: The rate of oxygen release would increase as light intensity increases

44. Question 5. Draw a graph to show the relationship between light intensity and the exchange of oxygen of a plant. Critical Thinking 8.1 (p. 11)

46. INVESTIGATION #1 Studying the effect of light intensity on gas exchange in leaves using hydrogencarbonate indicator

47. Introduction to Investigation In this investigation, you will study the effect of light intensity on gas exchange in leavesIn this investigation, you will study the effect of light intensity on gas exchange in leaves Green leaves will be put into different light intensities, and the level of carbon dioxide will be estimated by using hydrogencarbonate indicator solutionGreen leaves will be put into different light intensities, and the level of carbon dioxide will be estimated by using hydrogencarbonate indicator solution Note: Increase in CO2 – Orange to YellowNote: Increase in CO2 – Orange to Yellow Decrease in CO2 – Orange to Purple Decrease in CO2 – Orange to Purple

48. Procedure A B C D A B C D Please refer to pages 7 and 8 in your textbook

49. Results Table Colour of hydrogencarbonate indicator solution after one hour Tube A Tube B Tube C Tube D

50. INVESTIGATION #2 Studying the effect of light intensity on the gas exchange of a plant using a data logger

51. Introduction to Investigation In this investigation, you will study the effect of light intensity on the gas exchange of a water plant using a data loggerIn this investigation, you will study the effect of light intensity on the gas exchange of a water plant using a data logger Gas exchange in plants is affected by both the rates of respiration and photosynthesisGas exchange in plants is affected by both the rates of respiration and photosynthesis You can measure the rate of oxygen released by a water plant by measuring the change in pressure in an enclosed set-upYou can measure the rate of oxygen released by a water plant by measuring the change in pressure in an enclosed set-up A data logger and a low-pressure sensor can be usedA data logger and a low-pressure sensor can be used

52. Procedure Please refer to pages 8 and 9 in your textbook

53. Results Table Distance between the lamp and the conical flask (cm) Initial pressure Final pressure Change in pressure per minute 20 50 80 110

54. Discussion 1.What is the purpose of putting a water trough between the conical flask and the lamp? Ans: It is used to reduce the heating effect of the lamp. The result obtained is mainly due to the influence of the light intensity

55. Discussion 2.What is the purpose of using dilute sodium hydrogencarbonate solution in the conical flask? Ans: It provides carbon dioxide for the plant to carry out photosynthesis

56. Discussion 3.What is the relationship between the light intensity and the distance between the conical flask and the table lamp? Ans: The shorter the distance between the lamp and the conical flask, the stronger is the light intensity

57. Discussion 4.What is the relationship between the pressure in the conical flask and the light intensity in this experiment? Ans: The stronger the light intensity, the faster is the increase in pressure detected in the conical flask. The reason is that the rate of photosynthesis increases with light intensity, and the rate of oxygen release also increases

58. Photosynthesis Carbon Dioxide Water Carbon Oxygen Hydrogen

59. carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) fatty acids glycerol Combine to form fats and oils for construction of cell membranes and as a food storage Synthesis of Fats

60. 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 Synthesis of Proteins

61. Mineral Requirements in Plants In order to synthesize amino acids (i.e. proteins), plants must absorb minerals through the rootsIn order to synthesize amino acids (i.e. proteins), plants must absorb minerals through the roots Minerals that are required in large quantities: nitrogen, phosphorus, potassium, magnesium, sulphur and calciumMinerals that are required in large quantities: nitrogen, phosphorus, potassium, magnesium, sulphur and calcium Other minerals are also required but in a lesser amount: copper, zinc and ironOther minerals are also required but in a lesser amount: copper, zinc and iron A constant supply of minerals is necessary for the healthy development of a plantA constant supply of minerals is necessary for the healthy development of a plant

62. INVESTIGATION #3 Investigating the effects of minerals on plant growth using potted plants

63. Introduction to Investigation In this experiment, you will investigate the effects of different minerals on plant growthIn this experiment, you will investigate the effects of different minerals on plant growth Some of the plants will be watered with a solution lacking certain essential minerals, such as nitrogen and magnesiumSome of the plants will be watered with a solution lacking certain essential minerals, such as nitrogen and magnesium How will a lack of minerals affect the growth of a plant?How will a lack of minerals affect the growth of a plant?

64. Procedure Please refer to pages 12 and 13 in your textbook A B C

65. 1.Why do we use seedlings of similar size? 2.What differences in appearance of seedlings between pots A and B can you find at the end of the experiment? Ans: It is because seedlings of different size may differ in nutrient requirements, making it difficult to compare the results Ans: Seedlings in pot A grow healthy, but those in pot B show poor growth and small, yellowing of leaves Discussion

66. 3.What differences in appearance of seedlings between pots A and C can you find? 4.Why do we use sand but not garden soil in the pots? Ans: The seedlings in pot A grow healthy, but those in pot C also show poor growth and yellowing of leaves Ans: As garden soil may contain different minerals that plants need, accurate result of the effects of different minerals on plant growth may not be obtained Discussion

67. Discussion 5.What conclusion can you make from this experiment? Ans: Both nitrogen and magnesium are important to plant growth. Insufficient supply of these minerals would affect plant development

68. Note to Experiment A solution containing ALL the minerals that are required by a plant is called a complete culture solutionA solution containing ALL the minerals that are required by a plant is called a complete culture solution A solution which lacks certain essential minerals for plant growth is called a deficient culture solutionA solution which lacks certain essential minerals for plant growth is called a deficient culture solution Water cultures can be set up for the investigation of the effects of minerals on plant growthWater cultures can be set up for the investigation of the effects of minerals on plant growth

69. Hi! Its me again. Hmmm, there are a few things that I still dont understand. You mean, in addition to carbon dioxide, water and sunlight, plants also need to take in…arrr…what are those things called again? Oh…MINERALS…in order to grow healthily? Can someone PLEASE tell me how are these minerals important to plants? And what will happen if the plants do not take in these minerals?

70. Nitrogen Nitrogen is needed for the synthesis of amino acid (which are the building blocks for proteins)Nitrogen is needed for the synthesis of amino acid (which are the building blocks for proteins)

71. Structure of Amino Acid

72. Proteins in Plants Proteins are important for the synthesis of various plant structures: Proteins are important for the synthesis of various plant structures: Cell membraneCell membrane

73. Cell Membrane

74. Proteins in Plants Proteins are important for the synthesis of various plant structures: Proteins are important for the synthesis of various plant structures: Cell membraneCell membrane CytoplasmCytoplasm

75. Cytoplasm Reaction catalystReaction catalyst In various structures of the cellIn various structures of the cell

76. Proteins in Plants Proteins are important for the synthesis of various plant structures: Proteins are important for the synthesis of various plant structures: Cell membraneCell membrane CytoplasmCytoplasm EnzymeEnzyme HormoneHormone

77. Plant Hormones Chemicals made in one part of the plant that move to another part of the plant where, at very low concentrations, they regulate growth and/or developmentChemicals made in one part of the plant that move to another part of the plant where, at very low concentrations, they regulate growth and/or development Many different types of hormonesMany different types of hormones e.g. promotion of growth, promotion of cell division, etc.e.g. promotion of growth, promotion of cell division, etc.

78. Other Functions of Nitrogen DNA (in making the nitrogenous base)DNA (in making the nitrogenous base) ChlorophyllChlorophyll

79. Nitrogen in Soil Usable forms of nitrogen include nitrate (NO 3 - ) and ammonium (NH 4 + )Usable forms of nitrogen include nitrate (NO 3 - ) and ammonium (NH 4 + ) Nitrate is the more common form of nitrogen that is absorbed be plants from soilNitrate is the more common form of nitrogen that is absorbed be plants from soil However, most of the nitrogen in soil is NOT present as nitrate nor as ammoniumHowever, most of the nitrogen in soil is NOT present as nitrate nor as ammonium Nitrogen in soil must therefore be converted to the usable forms by soil microorganismsNitrogen in soil must therefore be converted to the usable forms by soil microorganisms

80. Nitrogen Deficiency A deficiency in nitrogen will result in: A deficiency in nitrogen will result in: Small and weak plantsSmall and weak plants Stunted growthStunted growth Yellowish leaves (Chlorosis)Yellowish leaves (Chlorosis)

81. Nitrogen Deficiency

82. Magnesium Most of the magnesium in the soil exists in forms which are not directly available to plantsMost of the magnesium in the soil exists in forms which are not directly available to plants Magnesium is taken up by plants as magnesium ions (Mg 2+ )Magnesium is taken up by plants as magnesium ions (Mg 2+ ) Magnesium is an essential component of chlorophyllMagnesium is an essential component of chlorophyll

83. Magnesium in Chlorophyll

84. Magnesium Most of the magnesium in the soil exists in forms which are not directly available to plantsMost of the magnesium in the soil exists in forms which are not directly available to plants Magnesium is taken up by plants as magnesium ions (Mg 2+ )Magnesium is taken up by plants as magnesium ions (Mg 2+ ) Magnesium is an essential component of chlorophyllMagnesium is an essential component of chlorophyll Magnesium also plays a role in enzymes activation, protein synthesis, etc.Magnesium also plays a role in enzymes activation, protein synthesis, etc.

85. Magnesium Deficiency A deficiency in magnesium will result in: A deficiency in magnesium will result in: ChlorosisChlorosis Growth can be reduced alsoGrowth can be reduced also

86. Magnesium Deficiency

87. Minerals SoilPlant Minerals in soil are taken up by plants, and can be released back into the soil by decomposition

88. Minerals Crops take up minerals from soilCrops take up minerals from soil When crops are harvested, minerals are removed from soilWhen crops are harvested, minerals are removed from soil Soil can also be washed away by rain waterSoil can also be washed away by rain water If there is a lack of minerals in soil, the production of crops might be affectedIf there is a lack of minerals in soil, the production of crops might be affected How can farmers prevent the depletion of minerals in soil?How can farmers prevent the depletion of minerals in soil?

89. Fertilizers Fertilizers are added to soil to replace the loss of mineralsFertilizers are added to soil to replace the loss of minerals Two kinds of fertilizers can be used:Two kinds of fertilizers can be used: - Natural fertilizers - Natural fertilizers - Chemical fertilizers - Chemical fertilizers

90. Natural Fertilizers Organic fertilizersOrganic fertilizers Made from organic substances, such as manure (animal wastes) and dead bodies of plants and animalsMade from organic substances, such as manure (animal wastes) and dead bodies of plants and animals Organic compounds in it are decomposed by the bacteria in soil to form mineral saltsOrganic compounds in it are decomposed by the bacteria in soil to form mineral salts

91. Chemical Fertilizers Man-made fertilizersMan-made fertilizers Made with inorganic compoundsMade with inorganic compounds Can result in pollution of the environment, such as algal bloomCan result in pollution of the environment, such as algal bloom

92. Comparison between natural and chemical fertilizers Natural fertilizers Contain humus which can improve soil texture Chemical fertilizers No humus so cannot improve soil texture

93. Humus Humus is the organic portion of soil, brown or black in color, consisting of partially or wholly decayed plant and animal matter that provides nutrients to plants and increases the ability of soil to retain waterHumus is the organic portion of soil, brown or black in color, consisting of partially or wholly decayed plant and animal matter that provides nutrients to plants and increases the ability of soil to retain water

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

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