6. Plant Nutrition Flashcards
1
Q
Photosynthesis definition
A
the process by which plants manufacture carbohydrates from raw materials using energy from light
2
Q
What are the raw materials for photosynthesis?
A
carbon dioxide and water
3
Q
What is the waste product of photosynthesis?
A
Oxygen
4
Q
Word equation for photosynthesis
A
light
carbon dioxide + water –> glucose + oxygen
chlorophyll
5
Q
Where is water for photosynthesis taken from?
A
Taken up by the roots and transported through the xylem to the leaves
6
Q
Where is carbon dioxide for photosynthesis taken from?
A
Diffuses into the leaf through the stomata
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
8
Q
What happens to oxygen produced by photosynthesis?
A
- Diffuses out of the leaf through the stomata
- used in respiration
9
Q
What is the balanced chemical equation for photosynthesis?
A
6CO2 + 6H2O —> C6H12O6 + 6O2
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
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
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
13
Q
What can glucose be converted into to be transported around the plant?
A
converted into sucrose
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.
15
Q
Where is starch stored?
A
Starch is stored in chloroplasts where photosynthesis occurs
16
Q
What test can be a reliable indicator of which parts of the leaf are photosynthesising?
A
testing a leaf for starch
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
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
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.
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
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
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
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
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
25
What can be a more accurate way of measuring the rate of photosynthesis rather than counting the number of bubbles produced?
- 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
26
What factors can be investigated to see how they influence the rate of photosynthesis?
- 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
27
What precautions must be taken when investigating the rate of photosynthesis?
Care must be taken when investigating a condition to keep all other variables constant in order to ensure a fair test
28
Why does a glass tank need to be used when when investigating changing light intensity?
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
29
What is the rate of photosynthesis limited by?
limited by whatever factor is the lowest at that time
30
What factors affect the rate of photosynthesis?
- light intensity
- carbon dioxide concentration
- temperature
31
Limiting factor definition
something present in the environment in such short supply that it restricts life processes
32
Why is water not considered a limiting factor?
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
33
How does temperature affect the rate of photosynthesis?
- 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
34
How does light intensity affect the rate of photosynthesis?
- 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
35
How does carbon dioxide concentration affect the rate of photosynthesis?
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
When can the knowledge of limiting factors be useful and why?
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
Why is it better for farmer to grow crops inside a green house rather than outside?
- 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
What conditions can be manipulated to increase the rate of photosynthesis in a greenhouse?
- 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
What is one problem with green houses for farmers?
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
What problem can occur in green houses in tropical countries?
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
When do plants respire and what do they take in/out?
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
When do plants photosynthesise and what do they take in/out?
Plants also photosynthesise during daylight hours, for which they need to take in carbon dioxide and release the oxygen made in photosynthesis
43
Where can chloroplasts be found in a leaf?
- palisade mesophyll cells
- spongy mesophyll cells
- guard cells (around stomata)
44
During the day, what is the difference between the rate of photosynthesis and respiration?
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
What is used to investigate the effect of light on the net gas exchange?
a pH indicator such as hydrogencarbonate indicator
46
Why is a pH indicator suitable to measure net gas exchange?
This is possible because carbon dioxide is an acidic gas when dissolved in water
47
What does a hydrogen carbonate indicator show?
Hydrogencarbonate indicator shows the carbon dioxide concentration in solution
48
What colour is hydrogen carbonate indicator at highest conc of CO2?
yellow
49
What colour is hydrogen carbonate indicator at higher (than atmospheric level) conc of CO2?
orange
50
What colour is hydrogen carbonate indicator at atmospheric level conc of CO2?
red
51
What colour is hydrogen carbonate indicator at lower (than atmospheric level) conc of CO2?
magenta
52
What colour is hydrogen carbonate indicator at lowest conc of CO2?
purple
53
What are the conditions in a plant when the hydrogen carbonate indicator is yellow or orange?
More respiration than photosynthesis
| - lower pH - more acidic
54
What are the conditions in a plant when the hydrogen carbonate indicator is red?
photosynthesis is occurring at an equal rate to respiration
55
What are the conditions in a plant when the hydrogen carbonate indicator is magenta or purple?
more photosynthesis than respiration
| - higher pH - more alkaline
56
How can a plant be tested for net gas exchange?
- 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
What conclusion can be made if the indicator turns purple?
There is a net intake of oxygen by a leaf in light
58
What conclusion can be made if the indicator turns yellow?
There is a net intake of carbon dioxide by a leaf in the dark
59
wax cuticle description
protective layer on top of the lead, prevents water from evaporating
60
upper epidermis description
thin and transparent to allow light to enter palisade mesophyll layer underneath it
61
palisade mesophyll description
column shaped cells tightly packed with chloroplasts to absorb more light, maximising photosynthesis
62
spongy mesophyll description
contains internal air spaces that increase the surface area to volume ratio for the diffusion of gases mainly carbon dioxide
63
lower epidermis description
contains guard cells and stomata
64
guard cell description
absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in, oxygen to diffuse out
65
stomata description
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
vascular bundle description
contains xylem and phloem to transport substances to and from the leaf
67
xylem description
transports water into the leaf for mesophyll cells to use in photosynthesis and for transpiration from stomata
68
phloem description
transports sucrose and amino acids around the plant
69
large surface area (leaf) adaptation
increases surface area for the diffusion of carbon dioxide and absorption of light for photosynthesis
70
thin (leaf) adaptation
allows carbon dioxide to diffuse to palisade mesophyll cells quickly
71
chlorophyll adaptation
absorbs light energy so that photosynthesis can take place
72
network of veins adaptation
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
stomata adaptation
allows carbon dioxide to diffuse into the lead and oxygen to diffuse out
74
epidermis is thin and transparent adaptation
allows more light to reach the (photosynthesising) palisade cells
75
thin cuticle made of wax adaptation
to protect the lead without blocking sunlight
76
palisade cell layer at top of leaf adaptation
maximises the absorption of light as it will hit chloroplasts in the cells directly
77
spongy layer adaptation
air spaces allow carbon dioxide to diffuse through the leaf, increasing the surface area
78
vascular bundles adaptation
thick cell walls of the tissue in the bundles help to support the stem and leaf
79
What type of biological molecules do plants contain?
- carbohydrates
- proteins
- lipids
- nucleic acid (DNA)
80
What elements do carbohydrates contain?
| What element do proteins also contain
Carbohydrates contain the elements carbon, hydrogen and oxygen
- nitrogen (and certain amino acids contain other elements too)
81
What elements does chlorophyll also contain
- magnesium and nitrogen
82
Where do plants get elements from?
Plants obtain these elements in the form of mineral ions actively absorbed from the soil by root hair cells
83
What is a mineral?
‘Mineral’ is a term used to describe any naturally occurring inorganic substance
84
magnesium function
magnesium is needed to make chlorophyll
85
signs of magnesium deficiency
causes yellowing between the veins of leaves (CHLOROSIS)
86
nitrate function
- nitrates are a source of nitrogen needed to make amino acids ( to build proteins)
87
signs of nitrate deficiency
causes stunted growth and yellowing of leaves
