Term 2a Flashcards
(20 cards)
What are the products of photosynthesis?
Produce starch for storage
Synthesis lipids for an energy source in seeds
To form cellulose to make cell walls
Produce amino acids
Photosynthesis equation
Carbon dioxide + water -> glucose + oxygen
What are the limiting factors of photosynthesis?
Temperature
Light intensity
Carbon dioxide concentration
How does temperature affect the rate of photosynthesis?
At high temperature the enzymes can denature and reduce the rate of photosynthesis.Lower temperature fewer successful collisions.
What effect does light intensity have on photosynthesis?
More light a plant receives, the faster the rate of photosynthesis.
What can affect the amount of chlorophyll?
Diseases
Lack Of nutrients
Loss of leaves
Genetic factor in the plant
Structure of leaf? And function
Structure
Description
Wax cuticle
Protective layer on top of the leaf, prevents water from evaporating
Upper epidermis
Thin and transparent to allow light to enter palisade mesophyll layer underneath it
Palisade mesophyll
Column-shaped cells tightly packed with chloroplasts to absorb more light, maximising photosynthesis
Spongy mesophyll
Contains internal air spaces that increase the surface area to volume ratio for the diffusion of gases (mainly carbon dioxide)
Lower epidermis
Contains guard cells and stomata
Guard cell
Absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in, oxygen to diffuse out
Stomata
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
Vascular bundle
Contains xylem and phloem to transport substances to and from the leaf
Xylem
Transports water into the leaf for mesophyll cells to use in photosynthesis and for transpiration from stomata
Phloem
Transports sucrose and amino acids around the plant
Experiment for light in photosynthesis
De-starch the plant by placing it 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 de-starching, partially cover a leaf of the plant with aluminium foil and place the plant in sunlight for a day
Remove the covered leaf and test for starch
Drop the leaf in boiling water
This kills the tissue and breaks down the cell walls
Transfer the leaf into hot ethanol in a boiling tube for 5-10 minutes
This removes the chlorophyll so colour changes from iodine can be seen more clearly
Rinse the leaf in cold water
This is done to soften the leaf tissue after being in ethanol
Spread the leaf out on a white tile and cover it with iodine solution
In a green leaf, the entire leaf will turn blue-black as photosynthesis is occurring in all areas of the leaf
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
When the cells can’t photosynthesise they break down the starch to use the glucose for respiration
Experiment carbon dioxide and photosynthesis ?
De-starch the plant by placing it 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 de-starching, enclose one leaf with a conical flask containing potassium hydroxide
The potassium hydroxide will absorb carbon dioxide from the surrounding air
Enclose another leaf with a conical flask containing no potassium hydroxide (control experiment)
Place the plant in bright light for several hours
Test both leaves for starch using iodine solution
Drop the leaf in boiling water
Transfer the leaf into hot ethanol in a boiling tube for 5-10 minutes
Rinse the leaf in cold water
Spread the leaf out on a white tile and cover it with iodine solution
The leaf from the conical flask containing potassium hydroxide will remain orange-brown as it could not photosynthesise due to lack of carbon dioxide
The leaf from the control conical flask not containing potassium hydroxide should turn blue-black as it had all necessary requirements for photosynthesis
Experiment for chlorophyll and photosynthesis?
Starch is stored in chloroplasts where photosynthesis occurs so testing a leaf for starch is a reliable indicator of which parts of the leaf are photosynthesising
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)
Drop the leaf in boiling water
This kills the tissue and breaks down the cell walls
Transfer the leaf into hot ethanol in a boiling tube for 5-10 minutes
This removes the chlorophyll so colour changes from iodine can be seen more clearly
Rinse the leaf in cold water
This is done to soften the leaf tissue after being in ethanol
Spread the leaf out on a white tile and cover it with iodine solution
Mineral ions needed for photosynthesis and why?
Magnesium: Megnesium is needed to make chlorophyll
Nitrate: Nitrates are a source of nitrogen needed to make amino acids(to build protein)
What does fertilisers do?
fertilisers increase the amount of key nutrients in the soil for crop plants, meaning that they can grow larger and are more healthy, which increases yields
Pesticides - these chemicals kill off unwanted insects and weed species, meaning that there is less damage done to crop plants by insects, as well as reducing competition from other plant species, which increases yields
Using fertilisers to increase crop yields?
Plants require a range of mineral ions in order to grow well
As crop plants take up these mineral ions from the soil, the mineral ions need to be replaced if crops are grown repeatedly in the same field (i.e. year after year)
Fertilisers are used to replace these mineral ions
They can make crops grow faster and bigger so that yields are increased
Fertilisers can be in the form of organic fertiliser or chemical fertiliser
Organic fertilisers commonly used by farmers include farmyard manure and compost
Chemical fertilisers are often applied to the soil as dry granules or can be sprayed on in liquid form
They mainly provide crop plants with nitrogen, phosphorus and potassium:
How does nitrogen increase crop yield?
Absorbed in the form of nitrates
Needed to make amino acids which are the building blocks of proteins
Lack of nitrogen causes weak growth and yellowing of the leaves of plants
How does phosphorous increase crop yields?
Absorbed in the form of phosphates
Needed to make DNA and cell membranes
Lack of phosphorus can cause poor root growth and discoloured leaves
How does potassium increase crop yield?
Absorbed in the form of various compounds of potassium
Allows enzyme reactions to take place to produce ATP in respiration as well as being needed for the enzymes involved in photosynthesis
Lack of potassium can cause poor growth of flowers and fruits, as well as brown spots on leaves
How does Glasshouse increase crop yield?
Artificial heating (enzymes controlling photosynthesis can work faster at slightly higher temperatures - only used in temperate 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
How does polythene tunnels increase crop yield?
More commonly called polytunnels, these are large plastic tunnels that cover crops
They can protect crops grown outside from the effects of the weather, including excessive wind, rain and extreme temperatures
They also increase the temperature slightly inside the tunnel
They can prevent the entry of pests that can damage plants or diseases that can kill plants
