Plant nutrition Flashcards
what is the chemical equation for photosynthesis
6CO2 + 6H2O = C6H12O6 + 6O2
what is photosynthesis
the conversion of light energy into glucose
how are leaves adapted for photosynthesis
leaves are broad so there is a large surface area for light absorption,
palisade mesophyll layer contains most chloroplasts so they are near the surface so can absorb more light,
upper epidermis is transparent so light can pass down to palisade layer,
waxy cuticle reduces evaporation
explain how light is a limiting factor for photosynthesis
chlorophyll absorbs light for photosynthesis, if the light supply increases so will rate of photosynthesis but only up to a certain point, where temperature and CO2 concentration take over as limiting factors
explain how Carbon Dioxide concentration is a limiting factor for photosynthesis
Needed as a reactant for photosynthesis however as long as supply is sufficient, up to a certain point, it will stop being a limiting factor and temperature will take over
explain how temperature is a limiting factor for photosynthesis
as temp. increases, so does the rate of photosynthesis until the temperature is too high and the plants enzymes are denatured, so the rate of photosynthesis decreases rapidly
how can you test a leaf for starch
boil the leaf in boiling water to stop all chemical reactions, put the leaf in a boiling tube with some ethanol and heat until it boils to remove chlorophyl, add iodine and if the leaf goes blue/black then starch is present
how can you show that a leave can photosynthesise using chlorophyl
take a variegated leaf that has been exposed to light, the green parts are where the chlorophyl is, test the leaf for starch using iodine, where the leaf is blue/black is where the chlorophyl is as it shows that photosynthesis has occurred as starch has been produced
how can you show that a leave can photosynthesise using CO2
place a soda lime and a plant in a dome with a light source just outside, the soda lime will absorb all of the CO2, test the plant for starch using iodine, it will not go blue/black, meaning no photosynthesis has occurred, showing CO2 is required for photosynthesis to occur
how can you show that light is needed for photosynthesis
leave a plant in a dark space for 48 hours, cut a leaf off of it, add a few drops of iodine solution, it will not go blue/black, showing no photosynthesis has occurred as no starch produced
explain how to show that oxygen production shows photosynthesis is occurring
place a light source a specific distance of a test tube containing Canadian pond weed, leave the pond weed to photosynthesis for a set amount of time, the oxygen will collect in the capillary tube. use a syringe to draw up the gas bubble alongside a ruler and the length of the gas bubble is measured. this is proportional to O2 production
why are nitrates required for plant growth
contain nitrogen for protein and amino acids. they help with cell growth and if a plant does not contain nitrates its growth will be stunted and older plants will go yellow
why are phosphates needed for plant growth
phosphorous for dna and membranes as well as respiration and growth. plants without phosphates will be purple when leaves are old
why is potassium needed for plant growth
to help enzymes for respiration and photosynthesis, plants without potassium will have discoloured leaves
why is magnesium needed for plant growth
makes chlorophyl, if not present then plant leaves are yellow
what is the role of the xylem
carry water and mineral salts from the roots up the shoot to the leaves in the transpiration stream
what is the role of the phloem
transport sugars e.g. sucrose from where they are made in the leaves to other parts of the plant, this is called translocation
how are root hair cells adapted
long hairs which stick out into the soil, each branch of a root containing millions of microscopic hairs to create a large surface area for water absorption by osmosis
what is transpiration
the loss of water from the plant caused by evaporation and diffusion from the surface. this creates a slight water shortage so more water is take in by the xylem vessels, leading to more water taken up from the roots, causing a constant transpiration stream
how does light intensity affect transpiration
brighter light = greater rate of transpiration as stoma are open to absorb carbon dioxide for photosynthesis, so water cab escape
how does temperature affect transpiration
increased temperature = increased rate of transpiration as water particles have more energy to evaporate and diffuse out of the stomata
how does wind speed affect transpiration
increased wind speed = increased transpiration as upon exit, water is swept away, maintaining a low conc. gradient. diffusion then happens quickly.
how does humidity affect transpiration
the drier the air around the leaf = the faster the rate of transpiration as the water concentration difference is greater, so more diffusion can occur
how can you increase humidity
use water spray
how can you increase wind speed
use a fan
why do you cut a shoot underwater in a potometer investigation
to prevent air entering the xylem
how can you airtight a system
apply Vaseline
why do you dry leaves in a potometer investigation
wet leaves will affect results
