Studied by 4 people
describe what a photosynthetic organism is
main producer of food and biomass (e.g. grass)
describe what type of reaction photosynthesis is
endothermic reaction
uses light energy
to react carbon dioxide and water
to produce glucose and oxygen
what are the products of photosynthesis
glucose and oxygen
what are the reactants of photosynthesis
carbon dioxide and water
describe how water and mineral ions enter a plant
water molecules are absorbed into root hair cells by osmosis
mineral ions are absorbed into root hair cells by active transport
“describe and explain how water moves through a plant”
hollow xylem vessels
made of dead cells
strengthened by lignin
carry water and mineral ions
from roots to leaves
by transpiration
where water evaporates from leaf’s surface
“describe and explain how sucrose moves through a plant”
phloem sieve tubes
made from living cells
carries sucrose in water
from leaves to roots
by translocation
describe how temperature effects the rate of photosynthesis
photosynthesis relies on enzyme action
increasing temperature increases rate of photosynthesis
as temperature increases past optimum, rate of reaction will decrease and eventually halt
as high temperatures can cause the enzymes to denature
meaning the reaction is not catalysed
describe how light intensity effects the rate of photosynthesis
light provides energy for the photosynthesis reaction
light intensity is directly proportional to the rate of reaction
as an increase in energy will increase the rate of reaction
describe how carbon dioxide concentration effects the rate of photosynthesis
carbon dioxide is a reactant in the photosynthesis reaction
carbon dioxide concentration is directly proportional to the rate of reaction
as an increase in carbon dioxide concentration will increase the rate of reaction
explain how light intensity and rate of photosynthesis are directly proportional
as light intensity increases the rate of photosynthesis also increases
this is because photosynthesis is an energy requiring reaction (endothermic)
more light energy will increase the rate at which oxygen is given off
explain how distance from light source and rate of photosynthesis are inversely proportional
as the distance increases, light intensity decreases
this is because as the distance away from a light source increases, light energy becomes spread over a wider area
decreasing the light intensity
meaning there is less light to provide energy for photosynthesis
state the inverse square law equation
1/(distance)²
core prac - investigating the effect of light intensity on the rate of photosynthesis (METHOD)
set up and LED lamp and a ruler pointing away from
make 5 tubes containing the same volume of water and hydrogencarbonate indicator
add the same number of plant to each test tube
cover one test tube with foil so it doesn’t receive any light (control)
set the test tubes up at different distances away from the lamp
leave for a fixed amount of time
remove the foil from the control
measure the colour of each solution against the hydrogencarbonate indicator scale
core prac - investigating the effect of light intensity on the rate of photosynthesis (RESULTS)
test tubes closer to the lamp will have a darker purple colour as they have a lower concentration of carbon dioxide
this is due to the increased rate of photosynthesis caused by increased light intensity
which has caused more carbon dioxide to be used as a reactant
state what positive phototropism is
when an object bends towards a light source
state what negative phototropism is
when an object bends away from a light source
state what positive gravitropism is
an objecting bending towards the direction of gravity
state what negative gravitropism
a plant growing away from the ground
state what types of tropism occur in the roots of plants
positive gravitropism
negative phototropism
state what types of tropism occur in the stems of plants
negative gravitropism
positive phototropism
explain how auxins affect plant growth and development in the shoots/stems
the tip of the shoot produces auxins
auxins are transported towards the shaded side of the shoot tip and diffuse down the shaded side
auxins in the shoot cause cell elongation
causing the positive phototropism in the shaded side of the shoot tip (shoot tip bends towards the light source)
explain how auxins affect plant growth and development in roots
the root produces auxins
gravity pulls the auxins to the bottom of the root
auxins in the root inhibit cell elongation
causing positive gravitropism (root bends down towards gravity)
explain how the large surface area of root hair cells is an adaptation to absorb water and mineral ions
it allows for an increased rate of osmosis and active transport
explain how the large amount of mitochondria in root hair cells is an adaptation to absorb water and mineral ions
the mitochondria allow for aerobic respiration
which provides energy for active transport and osmosis
of ions and water moleules into plant roots
explain how xylem vessels are adapted to their function in plants
tubes are made of dead cells (no cytoplasm or organelles) to allow water to flow through
enhanced with lignin
to make the cell walls stronger
so they’re less susceptible to damage
by changes in water pressure
explain how sieve tubes in phloem vessels are adapted to their function in plants
made of living cells
cells have no nuclei
tubes have perforated ends so cell cytoplasm connects together
sieve tubes have companion cells attached to provide energy for translocation
sucrose is transported through the cytoplasm of the sieve tubes
explain how companion cells in phloem vessels are adapted to their function in plants
the transport of sucrose and other substances requires energy
companion cells attached to sides of sieve tubes provide energy for sieve tubes
through containing large amounts of mitochondria
which release energy through aerobic respiration
explain transpiration process
water is drawn through xylem in continuous transpiration stream
from roots to leaves via stem
to replace water lost through transpiration
strong cohesion causes water in xylem to create a continuous column
transpiration causes tension on water column
causing stream to be pulled out of xylem vessels and evaporated on leaf’s surface
state what the function of the stomata are in transpiration
the size of the stomatal opening is used by the plant to control the rate of transpiration
it therefore limits the levels of water loss from the leaf
describe how sucrose is transported around the plant by translocation
sucrose are transported around the plant through phloem vessels
the sucrose is transported within cytoplasm in sieve tubes around the plant
energy for translocation in sieve tubes is provided by companion cells
explain the effect of light intensity on the rate of water uptake by plants (guard cells)
guard cells are responsive to light intensity
increasing light intensity causes the guard cells to become turgid
this causes the stomata to open
which increases rate of transpiration
causing root hair cells to absorb more water from the soil
to replace water lost
explain the effect of air movement on the rate of water uptake by plants
increased air movement = increased rates of transpiration
air movement moves saturated air away from the leaves
this places more tension on the water transpiration stream in the xylem vessels
causing increased rates of transpiration and evaporation of water molecules on the leaf’s surface
causing increased water absorption in root hair cells by osmosis to replace the lost water
explain the effect of temperature on the rate of water uptake by plants
increasing temperature increases rate of water uptake
as more water molecules evaporate from the leaf surface
placing excess tension on the continuous water transpiration stream in xylem vessels
causing increased rates of transpiration
which causes root hair cells in the plant roots to absorb more water through osmosis
to replace water lost
explain how to calculate rate of transpiration
use a bubble potometer to measure the amount of time it take for an air bubble to move a fixed distance towards the plant
use the equation: rate = distance/time to find the rate of transpiration
explain how the structure of a leaf is adapted for photosynthesis and gas exchange
large surface area - take in more sunlight for photosynthesis
thin - decrease time taken for carbon dioxide diffusion through the leaf
stomata - allows carbon dioxide to diffuse into the leaf for photosynthesis
guards cells - open or close stomata depending on external conditions
xylem vessels - transport water from the roots to the leaves for photosynthesis
contains chlorophyll - absorb sunlight for photosynthesis
explain how leaf size and shape is adapted to allow plants to survive extreme environments
in hot environments, leaf size is reduced to tiny spikes
this reduces water loss by transpiration by reducing the surface area of the lead
explain how the waxy cuticle is adapted to allow plants to survive extreme environments
the waxy cuticle is thicker on leaves in hot environments
this reduces water loss by transpiration
explain how the stomata is adapted to allow plants to survive extreme environments
in hot environments, leaves have a reduced number of stomata
this reduces water loss by transpiration
explain how auxins are used as weed killers
auxins are used as selective weed killers
that negatively effect the growth of broad-leaved plants
when the auxins are sprayed on the weeds, they cause rapid growth through cell elongation
this growth becomes uncontrollable and leads to the weed dying as it’s exhausted all its resources
explain who uses auxins as weed killers and why
farmers
as they are selective
and only target broad-leaved weeds
and not narrow-leaved crops
explain how auxins are used in rooting powders
the auxins in rooting powder can cause a cutting of plant to grow into a clone of the cutting
as they encourage rapid development of roots
explain who uses auxins in rooting powders and why
gardeners or farmers
who want to cheaply produce a high yield of cloned plants
explain how gibberellins can cause germination
a high concentration of gibberellins can cause seed germination
as gibberellins promote plant growth and development
through stimulating cell elongation
explain how gibberellins can promote flowering
as gibberellins are responsible for growth and development in plants
through cell elongation
they can end seed dormancy
and cause a plant to flower, even out of season
explain how gibberellins can cause an increase in fruit size
gibberellins can cause cell elongation
which makes the size of fruit bigger as its cells are more elongated
explain how gibberellins can create seedless fruits
seeds in fruit are only created when the plant is pollinated
gibberellins cause plant growth and development by stimulating cell elongation
if gibberellins are used on unpollinated plants, the fruits produced won’t contain any seeds
explain who uses gibberellins and why
gardeners or farmers
to be able to produce fruits and plants all year round
not just relying on the optimum external environment
explain who uses ethene and why
food industry
as it is easier to transport and store unripe fruits
