paper 2 memorise Flashcards
(57 cards)
describe photosynthetic organisms
main producers of biomass
describe photosynthesis
an endothermic reaction that uses light energy to react carbon dioxide and water to produce glucose and oxygen
what are the limiting factors of photosynthesis?
temperature, light intensity, carbon dioxide concentration
what is the relationship between rate of photosynthesis and light intensity?
directly proportional
what is the relationship between rate of photosynthesis and distance from light source?
inversely proportional
how is the structure of the xylem important for its function?
lignified dead cells transport water and minerals through the plant
how is the structure of the phloem important for its function?
living cells using energy to transport sucrose around the plant
what are auxins used for?
weed killers and rooting powders
what is gibberellin used for?
for germination, fruit and flower formation and the production of seedless fruit
what is ethene used for?
fruit ripening
how does temperature affect the rate of photosynthesis?
rate increases, but until a certain point then the enzymes denature and rate decreases
how does light intensity affect the rate of photosynthesis?
higher light intensity, higher rate of photosynthesis
how does carbon dioxide concentration affect the rate of photosynthesis?
its is needed to make glucose so rate increases
how is the structure of the root hair cells adapted to absorb water and mineral ions?
- have root hairs which give them a large surface area so more water can move in
- have a large vacuole which affects speed of movement of water
how is the structure of the xylem adapted to its function to transport water and minerals around the plant?
xylem is a hollow tube made of dead cells, these are lignified which helps the cells withstand pressure from the movement of the water
how is the structure of the phloem adapted to transport sucrose around the plant?
- cells form sieve plates so substances can move from cell to cell as the phloem is made of living cells
how are water and mineral ions transported through the plant by transpiration?
water moves into the plant via osmosis from the soil to the roots and is absorbed by the root hair cells. the water moves up the stem through the xylem via transpiration and is absorbed by the cells that need it. Otherwise the evaporate at the open stomata.
how is the structure of the leaf adapted for photosynthesis and gas exchange?
- stomata: minimise water loss by swelling and becoming flaccid
- palisade mesophyll layer there are lots of chlorophyll so lots of photosynthesis can take place
- waxy cuticle: transparent layer to make the plant waterproof
what are the environmental factors on the uptake of water?
light intensity, air movement and temperature
how does temperature affect water uptake of a plant?
higher temp then increased rate of transpiration because water immediately evaporates as soon as it reaches the leaf so more uptake is needed
how does air movement affect water uptake of a plant?
if its windy then water vapour is pushed off the plants so the plant will have to take up more water
how does light intensity affect water uptake of a plant?
more light so increased rate of transpiration because the plant will be able to photosynthesize more so it needs more water to do it
how does auxins control growth in the shoots?
they are positively phototrophic and negatively gravitropic. on the shaded side the auxins move there and stimulate the cells to grow more there. this bends the shoot towards the light.
because they are negatively gravitropic, the auxin moves to the lower side and the cells of the shoots grow more on the side with the most auxin. so the shoots bend away from the ground.
how do auxins control growth in the roots?
they are positively gravitropic and negatively phototropic.
