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IGCSE Biology - Extended > 6. Plant Nutrition > Flashcards

6. Plant Nutrition Flashcards

1
Q

Photosynthesis definition

A

the process by which plants manufacture carbohydrates from raw materials using energy from light

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2
Q

What are the raw materials for photosynthesis?

A

carbon dioxide and water

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3
Q

What is the waste product of photosynthesis?

A

Oxygen

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4
Q

Word equation for photosynthesis

A

light
carbon dioxide + water –> glucose + oxygen
chlorophyll

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5
Q

Where is water for photosynthesis taken from?

A

Taken up by the roots and transported through the xylem to the leaves

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6
Q

Where is carbon dioxide for photosynthesis taken from?

A

Diffuses into the leaf through the stomata

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7
Q

What is glucose in plants used for?

A

Used to make substances needed by the plant

- used in respiration as a source of energy

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8
Q

What happens to oxygen produced by photosynthesis?

A
  • Diffuses out of the leaf through the stomata

- used in respiration

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9
Q

What is the balanced chemical equation for photosynthesis?

A

6CO2 + 6H2O —> C6H12O6 + 6O2

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10
Q

What happens to the light energy during photosynthesis?

A

The light energy is converted into chemical energy in the bonds holding the atoms in the glucose molecules together

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11
Q

What substances (that the plant needs) can be made from glucose?

A

They can also convert it into:

  • starch for storage
  • into lipids for an energy source in seeds
  • into cellulose to make cell walls
  • into amino acids (used to make proteins) when combined with nitrogen and other mineral ions absorbed by roots
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12
Q

Why do plants convert glucose into starch, rather than keeping it as glucose?

A

It is insoluble, meaning it won’t affect osmosis in cells

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13
Q

What can glucose be converted into to be transported around the plant?

A

converted into sucrose

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14
Q

Why can leaves not be tested for glucose?

A

Although plants make glucose in photosynthesis, leaves cannot be tested for its presence as the glucose is quickly used, converted into other substances and transported or stored as starch.

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15
Q

Where is starch stored?

A

Starch is stored in chloroplasts where photosynthesis occurs

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16
Q

What test can be a reliable indicator of which parts of the leaf are photosynthesising?

A

testing a leaf for starch

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17
Q

Procedure for testing leaves for starch

A
  • A leaf is dropped in boiling water to kill and break down the cell walls
  • The leaf is left for 5-10 minutes in hot ethanol in a boiling tube. This removes the chlorophyll so colour changes from iodine can be seen more clearly
  • The leaf is dipped in boiling water to soften it
  • The leaf is spread out on a white tile and covered with iodine solution
  • In a green leaf, the entire leaf will turn blue-black as photosynthesis is occurring in all areas of the leaf
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18
Q

How does the results for testing leaves for starch change if the leaf is variegated?
What can this test also be used to test?

A
  • This method can also be used to test whether chlorophyll is needed for photosynthesis by using a variegated leaf (one that is partially green and partially white)
  • The white areas of the leaf contain no chlorophyll and when the leaf is tested only the areas that contain chlorophyll stain blue-black
  • The areas that had no chlorophyll remain orange-brown as no photosynthesis is occurring here and so no starch is stored
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19
Q

What safety precautions must be taken into account when testing a leaf for starch?

A

Care must be taken when carrying out this practical as ethanol is extremely flammable, so at that stage of the experiment the Bunsen burner should be turned off.

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20
Q

What is the safest way to heat ethanol when testing a leaf for starch?

A

The safest way to heat the ethanol is in an electric water bath rather than using a beaker over a Bunsen burner with an open flame

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21
Q

How can the experiment for testing leaves for starch be altered to show the need for light in photosynthesis?

A
  • Before starting the experiment the plant needs to be destarched by placing in a dark cupboard for 24 hours
  • This ensures that any starch already present in the leaves will be used up and will not affect the results of the experiment
  • Following destarching, a leaf of the plant can be partially covered with aluminium foil and the plant placed in sunlight for a day
  • The leaf can then be removed and tested for starch using iodine
  • The area of the leaf that was covered with aluminium foil will remain orange-brown as it did not receive any sunlight and could not photosynthesise, while the area exposed to sunlight will turn blue-black
  • This proves that light is necessary for photosynthesis and the production of starch
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22
Q

Procedure for The Need for Carbon Dioxide in Photosynthesis

A
  • Destarch a plant
  • Tie a clear bag containing sodium hydroxide, which will absorb carbon dioxide from the surrounding air, around one leaf
  • Tie a clear bag containing water (control experiment), which will not absorb carbon dioxide from the surrounding air, around another leaf
  • Place the plant in bright light for several hours.
  • Test both leaves for starch using iodine
  • The leaf from the bag containing sodium hydroxide will remain orange-brown as it could not photosynthesise due to lack of carbon dioxide
  • The leaf from the control bag containing water should turn blue-black as it had all necessary requirements for photosynthesis
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23
Q

What plants are usually used to investigate the rate of photosynthesis?

A

The plants usually used are Elodea or Camboba – types of pondweed

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24
Q

How is the rate of photosynthesis measured?

A
  • As photosynthesis occurs, oxygen gas produced is released
  • As the plant is in water, the oxygen released can be seen as bubbles leaving the cut end of the pondweed
  • The number of bubbles produced over a minute can be counted to record the rate
  • The more bubbles produced per minute, the faster the rate of photosynthesis
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25
Q

What can be a more accurate way of measuring the rate of photosynthesis rather than counting the number of bubbles produced?

A
  • A more accurate version of this experiment is to collect the oxygen released in a test tube inverted over the top of the pondweed over a longer period of time and then measure the volume of oxygen collected
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26
Q

What factors can be investigated to see how they influence the rate of photosynthesis?

A
  • Investigating the effect of changing light intensity, by moving a lamp different distances away from the beaker containing the pondweed
  • Investigating the effect of changing temperature, by changing the temperature of the water in the beaker
  • Investigating the effect of changing carbon dioxide concentration, by dissolving different amounts of sodium hydrogen carbonate in the water in the beaker
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27
Q

What precautions must be taken when investigating the rate of photosynthesis?

A

Care must be taken when investigating a condition to keep all other variables constant in order to ensure a fair test

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28
Q

Why does a glass tank need to be used when when investigating changing light intensity?

A

When investigating changing light intensity, a glass tank should be placed in between the lamp and the beaker to absorb heat from the lamp and so avoid changing the temperature of the water as well as the light intensity

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29
Q

What is the rate of photosynthesis limited by?

A

limited by whatever factor is the lowest at that time

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30
Q

What factors affect the rate of photosynthesis?

A
  • light intensity
  • carbon dioxide concentration
  • temperature
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31
Q

Limiting factor definition

A

something present in the environment in such short supply that it restricts life processes

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32
Q

Why is water not considered a limiting factor?

A

Although water is necessary for photosynthesis, it is not considered a limiting factor as the amount needed is relatively small compared to the amount of water transpired from a plant so there is hardly ever a situation where there is not enough water for photosynthesis

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33
Q

How does temperature affect the rate of photosynthesis?

A
  • As temperature increases the rate of photosynthesis increases as the reaction is controlled by enzymes
  • However, as the reaction is controlled by enzymes, this trend only continues up to a certain temperature beyond which the enzymes begin to denature and the rate of reaction decreases
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34
Q

How does light intensity affect the rate of photosynthesis?

A
  • The more light a plant receives, the faster the rate of photosynthesis
  • This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
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35
Q

How does carbon dioxide concentration affect the rate of photosynthesis?

A

Carbon dioxide is one of the raw materials required for photosynthesis
This means the more carbon dioxide that is present, the faster the reaction can occur
This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short sup

36
Q

When can the knowledge of limiting factors be useful and why?

A

The knowledge about limiting factors and how they affect the rate of photosynthesis can be used to help control factors in glass houses to ensure maximum crop yields for farmers

37
Q

Why is it better for farmer to grow crops inside a green house rather than outside?

A
  • Growing crops outside does not allow farmers to control any of these factors to increase growth of plants
  • In a glass house, several conditions can be manipulated to increase the rate of photosynthesis
38
Q

What conditions can be manipulated to increase the rate of photosynthesis in a greenhouse?

A
  • artificial heating (enzymes controlling photosynthesis can work faster at slightly higher temperatures – only used in temperature countries such as the UK)
  • artificial lighting (plants can photosynthesise for longer)
  • increasing carbon dioxide content of the air inside (plants can photosynthesise quicker)
  • regular watering
39
Q

What is one problem with green houses for farmers?

A

When considering the use of glasshouses and manipulating conditions like this, farmers need to balance the extra cost of providing heating, lighting and carbon dioxide against the increased income

40
Q

What problem can occur in green houses in tropical countries?

A

they may need to be ventilated to release hot air and avoid temperatures rising too high, which could cause the denaturation of the enzymes controlling the photosynthesis reaction

41
Q

When do plants respire and what do they take in/out?

A

Plants are respiring all the time and so plant cells are taking in oxygen and releasing carbon dioxide as a result of aerobic respiration

42
Q

When do plants photosynthesise and what do they take in/out?

A

Plants also photosynthesise during daylight hours, for which they need to take in carbon dioxide and release the oxygen made in photosynthesis

43
Q

Where can chloroplasts be found in a leaf?

A
  • palisade mesophyll cells
  • spongy mesophyll cells
  • guard cells (around stomata)
44
Q

During the day, what is the difference between the rate of photosynthesis and respiration?

A

During the day, especially when the sun is bright, plants are photosynthesising at a faster rate than they are respiring, so there is a net intake of carbon dioxide and a net output of oxygen

45
Q

What is used to investigate the effect of light on the net gas exchange?

A

a pH indicator such as hydrogencarbonate indicator

46
Q

Why is a pH indicator suitable to measure net gas exchange?

A

This is possible because carbon dioxide is an acidic gas when dissolved in water

47
Q

What does a hydrogen carbonate indicator show?

A

Hydrogencarbonate indicator shows the carbon dioxide concentration in solution

48
Q

What colour is hydrogen carbonate indicator at highest conc of CO2?

A

yellow

49
Q

What colour is hydrogen carbonate indicator at higher (than atmospheric level) conc of CO2?

A

orange

50
Q

What colour is hydrogen carbonate indicator at atmospheric level conc of CO2?

A

red

51
Q

What colour is hydrogen carbonate indicator at lower (than atmospheric level) conc of CO2?

A

magenta

52
Q

What colour is hydrogen carbonate indicator at lowest conc of CO2?

A

purple

53
Q

What are the conditions in a plant when the hydrogen carbonate indicator is yellow or orange?

A

More respiration than photosynthesis

- lower pH - more acidic

54
Q

What are the conditions in a plant when the hydrogen carbonate indicator is red?

A

photosynthesis is occurring at an equal rate to respiration

55
Q

What are the conditions in a plant when the hydrogen carbonate indicator is magenta or purple?

A

more photosynthesis than respiration

- higher pH - more alkaline

56
Q

How can a plant be tested for net gas exchange?

A
  • Several leaves from the same plant are placed in stoppered boiling tubes containing some hydrogen-carbonate indicator
  • The effect of light can then be investigated over a period of a few hours
57
Q

What conclusion can be made if the indicator turns purple?

A

There is a net intake of oxygen by a leaf in light

58
Q

What conclusion can be made if the indicator turns yellow?

A

There is a net intake of carbon dioxide by a leaf in the dark

59
Q

wax cuticle description

A

protective layer on top of the lead, prevents water from evaporating

60
Q

upper epidermis description

A

thin and transparent to allow light to enter palisade mesophyll layer underneath it

61
Q

palisade mesophyll description

A

column shaped cells tightly packed with chloroplasts to absorb more light, maximising photosynthesis

62
Q

spongy mesophyll description

A

contains internal air spaces that increase the surface area to volume ratio for the diffusion of gases mainly carbon dioxide

63
Q

lower epidermis description

A

contains guard cells and stomata

64
Q

guard cell description

A

absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in, oxygen to diffuse out

65
Q

stomata description

A

where gas exchange takes place; opens during the day, closes during the night. Evaporation of water also takes place from here. in most plants, found in much greater concentration on the underside of the leaf to reduce water loss

66
Q

vascular bundle description

A

contains xylem and phloem to transport substances to and from the leaf

67
Q

xylem description

A

transports water into the leaf for mesophyll cells to use in photosynthesis and for transpiration from stomata

68
Q

phloem description

A

transports sucrose and amino acids around the plant

69
Q

large surface area (leaf) adaptation

A

increases surface area for the diffusion of carbon dioxide and absorption of light for photosynthesis

70
Q

thin (leaf) adaptation

A

allows carbon dioxide to diffuse to palisade mesophyll cells quickly

71
Q

chlorophyll adaptation

A

absorbs light energy so that photosynthesis can take place

72
Q

network of veins adaptation

A

allows the transport of water to the cells of the leaf and carbohydrates from the leaf for photosynthesis (water for photosynthesis, carbohydrates as a products of photosynthesis)

73
Q

stomata adaptation

A

allows carbon dioxide to diffuse into the lead and oxygen to diffuse out

74
Q

epidermis is thin and transparent adaptation

A

allows more light to reach the (photosynthesising) palisade cells

75
Q

thin cuticle made of wax adaptation

A

to protect the lead without blocking sunlight

76
Q

palisade cell layer at top of leaf adaptation

A

maximises the absorption of light as it will hit chloroplasts in the cells directly

77
Q

spongy layer adaptation

A

air spaces allow carbon dioxide to diffuse through the leaf, increasing the surface area

78
Q

vascular bundles adaptation

A

thick cell walls of the tissue in the bundles help to support the stem and leaf

79
Q

What type of biological molecules do plants contain?

A
  • carbohydrates
  • proteins
  • lipids
  • nucleic acid (DNA)
80
Q

What elements do carbohydrates contain?

What element do proteins also contain

A

Carbohydrates contain the elements carbon, hydrogen and oxygen
- nitrogen (and certain amino acids contain other elements too)

81
Q

What elements does chlorophyll also contain

A
  • magnesium and nitrogen
82
Q

Where do plants get elements from?

A

Plants obtain these elements in the form of mineral ions actively absorbed from the soil by root hair cells

83
Q

What is a mineral?

A

‘Mineral’ is a term used to describe any naturally occurring inorganic substance

84
Q

magnesium function

A

magnesium is needed to make chlorophyll

85
Q

signs of magnesium deficiency

A

causes yellowing between the veins of leaves (CHLOROSIS)

86
Q

nitrate function

A
  • nitrates are a source of nitrogen needed to make amino acids ( to build proteins)
87
Q

signs of nitrate deficiency

A

causes stunted growth and yellowing of leaves

IGCSE Biology - Extended (22 decks)

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