1. Nutrition in Plants

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

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! Photosynthesis
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. Chloroplast
Spongy Mesophyll Cell
Air Space
Stoma
CO2

9. Palisade Mesophyll Cell
Chloroplast
Palisade Mesophyll Cell
Air Space
Stoma
CO2

10. Light reaction 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

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

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 CO2 to form carbohydrates
Water is formed as a by-product

14. Summary of Photosynthesis
6 CO2 + 6 H20
C6H12O6 + 6 O2
Light
Water
Carbon Dioxide H
Light Reaction
Dark Reaction
Glucose
(C6H12O6)
Oxygen

15. Fate of carbohydrate products in the plant

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

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

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

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

20. join together to become protein molecules
carbon dioxide and water
photosynthesis
mineral salts from soil
(e.g. NO3-, SO42-)
carbohydrates (e.g. glucose)
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
To test a leaf for the presence of Starch

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

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

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

27. Why is the leaf put in hot water after being boiled in alcohol ?
boiling water
turn off Bunsen burner
boiling alcohol
hot water
iodine
white tile
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.

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

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

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

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

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

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

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

35. sunlight B A
water
potassium hydroxide solution
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.

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

37. Factors affecting the rate of photosynthesis

38.  Rate of Photosynthesis
Light Intensity
 Light intensity
 Rate of Photosynthesis

39. Carbon Dioxide Concentration
 Rate of Photosynthesis

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

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

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
chloroplasts
spongy mesophyll
intercellular space (air space)
guard cell
lower epidermis
stoma
cuticle

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
spongy mesophyll (layer)

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

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

56. guard cells
control the size of stoma

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

58. vascular bundle (vein)

59. Internal Structure of Leaf
xylem
phloem
The .. after a label = the end of labels.

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 broad & flattened
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 stomata 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
Much cheaper
Very expensive
Less soluble in water so more difficult to be absorbed
Very soluble in water so easier to be absorbed
Time is needed for the decomposition to complete before nutrients are available to plants
More readily to be used by the plants

77. ~ END ~