Plant Biology Flashcards
What is photosynthesis?
When single celled organisms convert light energy into chemical energy.
What is the word equation for photosynthesis?
carbon dioxide + water -> glucose + oxygen
What is the symbol equation for photosyntheses?
6CO2 + 6H2O -> C6H12O6 + 6O2
What is a leaf?
The organ of the plant that carries out photosynthesis.
What do leaf cells contain?
Chloroplasts. Chloroplasts contain chlorophyll which absorbs light energy.
How are leaves adapted for their function?
- large surface area to absorb light
- thin, short diffusion distance
- veins, support the leaf and transport water into the leaf
- waxy surface stops leaves losing water
What is the structure of the leaf?
wax cuticle upper epidermis palisade layer spongy layer lower epidermis stoma / guard cells
How do you test a leaf for starch?
- leaf in boiling water for 3 mins
- place leaf in ethanol then in hot water bath
- leave until ethanol stops bubbling
- put leaf in hot water
- add iodine
What is a destarched leaf?
A plant that has been kept in a dark cupboard, it has no light therefore it cannot photosynthesise.
What would the results of a starch test on a destarched plant be?
There is no starch present so the iodine will stay orange brown.
What factors affect photosynthesis?
- temperature
- light intensity
- CO2 concentration
What are leaves designed to do?
Absorb light and take in CO2. They contain veins that bring in the water taken up by the roots.
What is the rate of photosynthesis?
How fast a plant carries out photosynthesis
Explain why greenhouse owners burn paraffin in their greenhouses
This makes heat and carbon dioxide, which could be limiting factors. If there is more carbon dioxide and its warmer they hope that photosynthesis will be faster. They will be wasting their money if light is the limiting factor as they could also use an artificial light.
Describe the practical that proves shows if carbon dioxide is necessary for photosynthesis
- get a destarched plant
- put the destarched plant in a bell jar with soda lime to remove the carbon dioxide from the air.
- leave for 24 hours in a light place.
- test leaves for starch with iodine
If CO2 is needed the leaves will not go blue/black
What are nitrate ions used for?
making proteins and amino acids
Where are nitrate ions obtained from?
soil through root hairs
What is water used for?
photosynthesis
Where is water obtained from?
soil through root hairs
What are magnesium ions used for?
making chlorophyll
Where are magnesium ions obtained from?
soil through root hairs
What is carbon dioxide used for?
photosynthesis
Where is carbon dioxide obtained from?
the air
How are substances transported round plants?
in veins
What is the function of xylem?
transports water and mineral ions from the root to all parts of the plant.
What are the characteristics of xylem?
thick walls
hollow
What is the function of phloem?
Transports sucrose and amino acids from leaves to other parts of the plant.
What is phloem made of?
Living cells containing cytoplasm, but no nucleus.
What are the characteristics of a phloem tube?
nucleus
cell walls not thickened
cytoplasm
companion cell
How do gasses diffuse in leaves?
They diffuse in and out through the stomata
When are stomata open and when are they closed?
They open in the day when it is light to let air in. They are closed at night when there is no light.
What happens to the stomata when the plant is dry?
They close to reduce water loss
What is transpiration?
The loss of water vapour from a plant.
How does water move out of plants and into the air?
Diffuses out through the stomata onto the leaf, then it evaporates.
What is the function of the root hair cell?
to absorb water
How are root hair cells adapted to their function?
They have a large surface area
What factors affect transpiration?
temperature
wind speed
humidity
light
How are mineral ions absorbed from the soil?
by active transport
What do shoots grow towards and away from?
Towards light
Away from the force of gravity
Why do shoots grow towards light?
so they can get light for photosynthesis
What do roots grow towards and away from?
Towards force of gravity
Away from light
Why do roots grow towards the force of gravity?
To get water from the soil to support the plant.
What is phototropism?
responds to light
What is geotropism?
responds to gravity
What is a geotropic response?
they make sure roots grow down and shoots grow up
What causes phototropic reactions?
changes in auxin concentration
What is auxin?
plant hormone
Where is auxin made?
in the tips of the shoots
What does auxin do?
makes cells in a plants stem, makes the stem grow longer.
How does auxin react if the light is only from one side?
The auxin moves to the shady side, the cells on the shady side grow longer, the stem bends towards the light.
What does hydrogen carbonate indicator show?
How much CO2 is in the air
How does hydrogen carbonate indicator show how much CO2 is in the air?
same as air - red
CO2 removed - purple
CO2 added - yellow
