plant nutrition and transport Flashcards
what is photosynthesis
it is the process that produces food in plants, the food it produces is glucose
where does photosynthesis happen
in the leaves of all green plants, this is largely what the leaves are for
photosynthesis happens in…
chloroplast which are found in leaf cells and other green parts of the plant
chloroplast contain a pigment called chlorophyll which absorb sunlight and uses its energy to convert carbon dioxide and water into glucose, oxygen is also produced
why is photosynthesis an important process
because it converts light energy to chemical energy, which is stored in the glucose
this chemical energy is released when glucose is broken down during respiration
a simple explanation of photosynthesis
-Photosynthesis is the process that plants use to make their own food. They take in carbon dioxide (CO₂) from the air and water (H₂O) from the soil, and with the help of sunlight and a green pigment called chlorophyll, they produce glucose (a type of sugar) and oxygen (O₂).
- Provides Food:
Plants make glucose to grow and store energy. This energy is passed on to animals and humans when they eat plants.
Releases Oxygen:
Photosynthesis produces oxygen, which humans and animals need to breathe.
Maintains Balance:
It helps remove carbon dioxide from the air, keeping the atmosphere stable.
word and symbol equations for photosynthesis
carbon dioxide + water => glucose + oxygen
what is a limiting factor
something that stops photosynthesis from happening any faster
light intesity , CO2 concentration and temperature can all be the limiting factor
3 limiting factors
- light intensity (wave length + color)
- CO2 concentration
- temp (enzymes)
what do limiting factors depend on
the limiting factor depends on the environmental conditions. eg. in winter low temps might be the limiting factor. at night, light is likely to be the limiting factor
state –> not enough light slows down the rate of photosynthesis
light intesity and the effect of photosynthesis
- chlorophyll uses light energy to preform photosynthesis
- it can only do it as quickly as the light is arriving
- if the light intestity is increased, the rate of photosynthesis will increase steadily, but only up to a certain point
beyond that it wont make any difference because then it will be either the temp or CO2 level which is now the limiting factor
state -> too little CO2 slows down the rate of photosynthesis.
effect of CO2 on photosynthesis
as with the light intesity , increasing the concentration of CO2 will only increase the rate of photosynthesis up to a certain point. After this the graph flattens out, showing that CO2 is no longer the limiting factor.
as long as light and CO2 are in plentiful supply then the factor limiting photosynthesis must be temperature
effect of temp of photosynthesis
as the temp increases so does the rate of photosynthesis to a certain point
if the temp is too high (over about 45 degrees) the plants enzymes will denature so the rate of photosynthesis rapidly decreases.
usually if the temp is the limiting factor its because its too low, and things need warming up a bit
what are leaves designed for
making food by photosynthesis
MEMORISE THE DESIGN FOR LEAVES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
what are all the parts for leaves
- palisade mesophyll layer
- spongy mesophyll layer
- air space
- stoma
- guard cell
- waxy cuticle
- lower epidermis
- vascular bundle
- chloroplasts
- upper epidermis
Peter Saw A Small Green Worm Lying Very Calm Underwater
state –> leaves are broad so there is a large surface area exposed to light
where are most of the chloroplasts found
in the palisade layer since they can get the most light
why is the upper epidermis transparent
the upper epidermis transparent so that light can pass through it to the palisade layer
what are vascular bundles
they are transport vessels xylem and phloem. they deliver water and other nutrients to every part of the leaf and take away the glucose produced by photosynthesis. they also help to support the leaf stucture
what does the waxy cuticle do
helps to reduce water loss by evaporation
what do the adaptions of leaves for efficient gas exchange do
make photosynthesis more efficient. eg. the lower surface is full of little holes called stomata. which let CO2 diffuse directly into the leaf
why do plants need three main mineral ions for growth
- so they can produce important compounds
- they get these elements from mineral ions in the soil
if there are not enough of these mineral ions in the soil, plants suffer from deficiency symptoms
what 4 main minerals ions are needed for growth
- nitrates
- phosphates
- potassium
- magnesium
phosphates
contain phosphorus for making DNA and cell membranes and they are needed for respiration and growth. plants without enough phosphate have poor root growth and their older leaves are purple
nitrates
contain nitrogen for making amino acids and proteins.
these are needed for cell growth. if a plant cant get enough nitrates it will be stunted and older leaves will turn yellow
potassium
to help the enzymes needed for photosynthesis and respiration. if there is not enough potassium in the soil, plants have poor flower and fruit growth and discoloured leaves.
why is magnesium needed in small amounts
- magnesium is required for making chlorophyll which is needed for photosynthesis
- plants without enough magnesium have yellow leaves
test leaf for starch
- dunk leaf in boiling water
- put leaf in boiling tube with some ethanol and heat in an electric water bath until it boils - this gets rid of any chlorophyll and makes leaf white colour
- rinse leaf in cold water and add few drops of iodine solution, if starch is present the leaf will turn blue-black.
what does the starch test show
whether photosynthesis is taking place
if a plant cant photosynthesise…
it cannot make starch
how do you show that chlorophyll is needed for photosynthesis
using variegated (green and white) leaves. Only the green part contains chlorophyll.
- take a variegated leaf from a plant that has been exposed to light for a bit. Record which bits are green and which are not.
- test the leaf for starch. Only the bits that are green will turn blue-black.
- this suggests that only the parts of the leaf that contain chlorophyll are able to photosynthesise and produce starch.
how to show that CO2 is needed for photosynthesis.
You need a sealed bell jar, soda lime, a plant, and a light source (lamp)
- the soda lime will absorb CO2 out of the air into the jar
- if you leave the plant in the jar for a while and test a leaf for starch, it wont turn blue-black
- this shows that no starch has been made in the leaf, which means that CO2 is needed for photosynthesis
how do you show that light is needed for photosynthesis
- you need a plant that has been grown without ant light. eg in a cupboard for 48 hours. this will mean that it has used up its starch stores.
- cut a leaf from the plant and test it for starch using iodine solution. the leaf will not turn blue-black
- this shows that light is needed for photosynthesis, as no starch has been made.
how do you make the no light in plant experiment a fair test
you need to make sure that it is warm enough to photosynthesise and that there is plenty of CO2 or it will not be a fair test.
what does oxygen production show
it shows the rate of photosynthesis
what can be used to measure the effect of light intensity on the rate of photosynthesis
- canadian pondweed.
- the rate at which the pondweed produces oxygen corresponds to the rate at which it is photosynthesising.
- the faster the rate of oxygen production, the faster the rate of photosynthesis
how do you do the oxygen production showing the rate of photosynthesis test
- you need a ruler to vary the distance from plant, a light source, a clamp, syringe, canadian pondweed, water, sodium hydrogencarbonate, capillary tube
- the gas syringe should be empty to start with. sodium hydrogencarbonate may be added to the water to make sure the plant has enough carbon dioxide. ( it released the CO2 into the solution)
- a source of white light is placed at a specific distance from the pondweed.
- the pondweed is left to photosynthesise for a set amount of time. as it photosynthesises, the oxygen released will be collected in the capillary tube.
- at the end of the experiment, the syringe is used to draw out the gas bubble in the tube up alongside a ruler and the length of the gas bubble is measured. this is proportional to the volume of oxygen produced.
- for this experiment any variables such as the temp or the time the pondweed is left to photosynthesise is controlled.
- the experiment is repeated with the light source placed at different . distances from the pondweed.
what is transpiration
the loss of water from the plant
what is transpiration caused by
the evaporation and diffusion of water from a plant’s surface
where does most transpiration happen
at the leaves
what does the evaporation create
a slight shortage of water in the leaf and so more water is drawn up from the rest of the plant through the xylem vessels to replace it
this intern means more water is being drawn from the root and so there is a constant transpiration stream of water through the plant
state –> transpiration is the side effect of the way leaves are adapted for photosynthesis.
they have to have stomata in them so that gases can be exchanged easily.
bcs theres more water inside the plant than in the air outside, the water escapes from the leaves through the stomata by diffusion.
what are the 4 main factors that transpiration is affected by
light intesity, temp, wind speed, humidity
light intensity
the brighter the light, the greater the transpiration rate
stomata begin to close as it gets darker.
photosynthesis cannot happen in the dark, so they do not need to be open to let CO2 in. when the stomata is closed , very little water can escape
temp
the warmer it is, the faster transpiration happens.
when it is warm, the water particles have more energy to evaporate and diffuse out of the stomata
wind speed
the higher the wind speed around a leaf, the greater the transpiration rate.
if wind speed around a leaf is low, the water vapour just surrounds the leaf and does not move away. this means there is a high concentration of water particles outside the leaf as well as inside it, so diffusion doesnt happen quickly
if it is windy, the water vapour is swept away, maintaining a low concentration of water in the air outside the leaf. diffusion then happens quickly, from an area of high concentration to an area of low concentration
humidity
the drier the air around a leaf, the faster transpiration happens.
this is like what happens with air movement. if the air is humid there is a lot of water in it already, so there is not much of a difference between the inside and outside of the leaf.
diffusion happens fastest if there is a really high concentration in one place, and a really low concentration in the other.
what is a potmeter
a special piece of apparatus used to estimate transpiration rates
measuring transpiration
- cut a shoot underwater to prevent air from entering the xylem. cut it at a slant to increase the surface area available for water uptake
- assemble the potometer in water and insert the shoot under water , so no air can enter
- remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water.
- check the apparatus is watertight and airtight
- dry the leaves and allow time for the shoot to acclimatise and then shut the tap
- remove the end of the capillary tube from the beaker of water until one air bubble has formed, then put the end of the tube back into the water.
- record the starting position of the air bubble.
- start the stopwatch and record the distance moved by the bubble per unit time, eg per hour
- keep the conditions constant throughout the experiment, eg temp and air humidity
what do all cell organisms need to get rid of
waste substances
unicellular organisms - waste substances
these substances can diffuse directly in and out of the cell across the cell membrane. the diffusion is quick because of the short distances substances have to travel
what are the two main transport systems
- xylem tubes that transport water and minerals
- phloem tubes that transport food
multicellular organisms - waste substances
multicellular organisms ( animals and plants ) direct diffusion from the outer surface would be too slow - that is because substances would have to travel large distances to reach every cell.
so multicellular organisms need transport systems to move substances to and from individual cells quickly
xylem
the xylem carry water and mineral salts from the roots up the shoot to the leaves in the transpiratiion stream
phloem
- the phloem transport sugars, like sucrose and amino acids from where they are made in the leaves to other parts of the plant
- this movement of food substances around the plant is known as translocation
what do root hairs do
take in water
root hairs take in water…
- the cells on plant roots grow into long hairs which stick out into the soil
- each branch of a root will be covered in millions of these microscopic hairs
- this gives the plant a big surface area for absorbing water from the soil
what is water taken in by
osmosis - there is usually a higher concentration of water in the soil than there is inside the plant, so the water is drawn into the root hair cell by osmosis
what do root hair cells also take in
minerals, this is done by active transport
