photosynthesis and leaf structure Flashcards
word equation for photosynthesis
carbon dioxide + water -> oxygen + glucose
symbol equation for photosynthesis
6CO2 + 6H2O -> 6O2 + C6H12O6
which organelle does photosynthesis occur in? what pigment is needed?
chloroplasts
-> need chlorophyll
when does photosynthesis occur?
in high light intensities
which part of the plant have the most chloroplasts and why?
palisade mesophyll cells
-> they are tightly packed and near the top of the plant
which part of the plant has no chloroplasts and why?
roots
-> they are not exposed to sunlight
what is chlorophyll
a green pigment that absorbs the light energy needed for the reaction to take place
rate of photosynthesis in darkness
low
rate of photosynthesis in low light
medium
rate of photosynthesis in bright light
high
function of the waxy cuticle
- reduce water loss by evaporation by waterproofing the leaves
- wax secreted by cells of upper epidermis
- barrier to disease causing microorganisms
function of the upper epidermis
- thin and relatively transparent - allows sunlight to reach the palisade mesophyll for photosynthesis
function of the palisade mesophyll
- column shaped, thin and arranged close together
- contains many chloroplasts and densely packed so that as much light energy can be absorbed as possible for efficient photosynthesis
function of the vascular bundles
- contains the xylem which transports water and mineral salts from the roots to the leaves
- contains the phloem which carries organic products of photosynthesis around the plant (e.g. sucrose and amino acids)
- cannot transport starch because it is too big and insoluble
function of the spongey mesophyll
- have fewer chloroplasts compared to palisade but can still photosynthesise
- main gas exchange surface, absorbing CO2 in daylight and releasing O2 and H2O
- loosely packed with large space, helps in the diffusion of gasses through leaves
- saturated with water vapour, helps in absorption of gases
function of the lower epidermis
- act as a protective layer, contains more stomata compared to upper epidermis to regulate loss of water and site of gaseous exchange into and out of cell
function of chloroplasts
- site of photosynthesis
- contains the pigment chlorophyll which is green in colour
function of stomata
- regulates water loss (transpiration)
- site of gaseous exchange in leaf
function of guard cells
- control opening and closing of stomata to allow CO2 in during light to allow photosynthesis to occur
how does the structure of a leaf allow it to be adapted for gas exchange?
spongey mesophyll
- loosely packed with lots of gaps
-> allows more SA for diffusion of gases
-> CO2 in daylight
-> O2 released
guard cells
- control opening and closing of stomata
- opens in daylight to allow CO2 for photosynthesis
method to test for photosynthesis in plants
- remove a variegated leaf
- pour boiling water into a beaker
- dip leaves in hot water for 10-20 secs
- add 10ml ethanol to test tube and add leaf
- leave test tube in beaker of hot water for 5 mins
- remove leaf and rinse with cold water
- place leaf on dropping tile and cover with iodine
- if blue/black colour shows, starch is present
results of the testing for photosynthesis in plants practical
green bit (with chloroplasts) changed colour as photosynthesis was taking place
method to measure rate of photosynthesis using pond weed:
- put pond weed in water and move lamp 10cm away
- let plant acclimatise
- count number of bubbles in one min
- move lamp 10cm further away and let plant acclimatise
- count number of bubbles in one min
- repeat, moving lamp back until 50cm away
- repeat 3x and find average
limiting factors of photosynthesis:
- light intensity
- temp
- CO2 concentration
light intensity (limiting factor of photosynthesis):
- as light intensity increases, rate of photosynthesis increases
- the graph levels off due to another factor becoming limiting (temp or CO2)
carbon dioxide (limiting factor of photosynthesis):
- as CO2 concentration increases, the rate of photosynthesis increases
- the levels off due to another factor becoming the limiting (light or temp)
temperature (limiting factor of photosynthesis):
- as temp increases, rate of photosynthesis increases
- graph drops off because enzymes denature
what does the number of chloroplasts in a plant affect?
the rate of photosynthesis
what can the amount of chloroplasts be affected by?
- disease
- lack of nutrients
- loss of leaves
diffusion definition
the net movement of particles from a high to low concentration
4 factors that influence the rate of diffusion:
- distance
- SA : vol
- temp
- concentration gradient
active transport definition
movement of particles against the concentration gradient (low to high concentration)
is active transport an active process
yes, it requires energy from respiration
examples when particles need to move against concentration gradient
small intestine - ileum
root hair cells - actively transport mineral ions
use of nitrates
- amino acids
- proteins
- chlorophyll
- DNA
nitrate deficiency symptoms in plants
- stunted growth of plants
- older leaves turn yellow
phosphate use
- DNA
- part of cell membrane
phosphate deficiency symptoms in plants
- poor root growth
- younger leaves turn purple
potassium use
- enzymes for respiration and photosynthesis to work
potassium deficiency symptoms in plants
leaves turn yellow with dead spots
magnesium use
part of chlorophyll molecule
magnesium deficiency symptoms in plants
leaves turn yellow
what minerals MUST a plant absorb through the soil
- nitrate
- phosphate
- potassium
- magnesium
when testing for the production of starch in plants why does the leaf needed to be dipped in boiling water for 10-20 seconds
to make the leaf more permeable by altering the shape of the protein in the membrane
when testing for the production of starch in plants why does the leaf need to be in boiling ethanol for 5 minutes
to get rid of the chlorophyll so we can see the colour change when we add the iodine
