Plant structures Flashcards
Equation for photosynthesis
carbon dioxide + water → glucose + oxygen
How does carbon dioxide diffuse?
Carbon dioxide diffuses through the leaf through the stomata
Water is taken up by the root from the soil and then transported by the leaves by the xylem
Why do plants need glucose
- Cellular respiration to release energy
- Make cellulose (coplex carbohydrates) - strenghten cell walls
- Make starch for long term storage - break at night
- Making amino acids combine glucose with nitrate ions from soil making proteins
- Making oils and fats
Is photosynthesis endothermic or exothermic?
Endothermic
Uses energy from the sun
How does chlorophyll affect photosynthesis?
Chlorophyll which is found in chloroplast absorbs light energy
So if plants have less of it they won’t be able to carry out much photosynthesis
They can have less chlorophyll by :
viruses, lack of nutrience and environmental stress
which all damage chloroplasts
How does light intensity affect photosynthesis?
As light intensity increases so does the rate of photosythesis as it relys on the energy from the sun.
But it only increases till a point till it’s plateaued and theres something else limiting photosynthesis like CO2
How does Co2 concentration affect photosynthesis?
Co2 is a reactant of photosynthesis so the higher the co2 concentration the faster the rate of photosynthesis.
After a while, it plateaus because when carbon dioxide is plentiful something else will become the limiting factor
How does temperature affect photosynthesis?
At first the rate of photosynthesis rises with temperature as the particles have more energy and move more quickly. This means they can react more quickly and so the rate is higher.
However, as temperature rises above the optimum temperature for the enzymes involved, the enzymes may start to break down. This decreases the rate until it falls to zero (when the enzymes are denatured).
How do farmer artifically create good conditions for plants?
- Place there plants in greenhouses so it traps heat so increase in temperature
- Provide artificial light so photosynthesis can continue after at night
- Pump co2 (paraffin heater) release carbon dioxide and heat as it burns
- They are closed so pest cant get in
- Use fertilisers so minerals are in soil
What is the top and bottom of the leaf called?
It’s a layer of vety thin cells called epidermal cells which form epidermal tissue
They protect the surface of the leaf
How is the upper epidermis adapted?
It is transparent allowing light to pass through to the photosynthic cells below
And the leaf has a waxy cuticle (thin layer of lipids) on top to reducing the evaportation of water from the surface
This helps prevent the leavefrom drying out
Whats the function of the stomata
And where is it found?
The lower epidermis have tiny pores called stomata
Allow co2 to enter the leaf and oxygen to leave
Also help to control the amout of water vapour that pass out of the leaf
Open for short time to reduce water loss
Where is the palisde mesophyll layer found?
At the top it’s made up of palisade cells which are packed full of chloroplasts
Key feature of the spongy mesophyll layer?
Full of air spaces, which allow co2 to diffuse from the stomata through the spongy mesophyll palisade cells
Oxygen also diffuses from the palisade cells through the spongy mesophyll to the stomata
Guard cells
Found between stomata
They will be well hydrated making the gap of the stomata larger allowing more Co2 to diffuse through
And when the plant is short of water the guard cells will lose water due to osmosis conserving water vapour and co2 can’t get in
