section c: plant physiology Flashcards
what is photosynthesis
the process where carbon dioxide and water are combined to make carbohydrates (glucose) using light energy. oxygen is formed as a waste product.
what is chlorophyll
the green molecule contained inside chloroplasts that absorbs sunlight energy in order for photosynthesis to take place.
what is a chloroplast
the organelle that contains chlorophyll
cuticle
waxy surface of the leaf
what is underneath the cuticle
the upper epidermis
what is underneath the upper epidermis
palisade cells
what is underneath the palisade cells
spongy cells
what is the mesophyll layer
the palisade cells and the spongy cells of a leaf
what are guard cells
cells surrounding the stoma (a hole within the lower epidermis which allows carbon dioxide in) that can close it when needed.
what is the bottom layer of a leaf
the lower epidermis
xylem
where water and ions go up to the leaf
phloem
supplies the other parts of the plant (roots) with the products of photosynthesis (food)
rate of photosynthesis during the day
plants will absorb more carbon dioxide as they have access to more sunlight during the day enabling a higher rate of photosynthesis
what is starch
a polysaccharide (a chain of glucose molecules put together)
how do you test a leaf for starch
- dewax in boiling water
- remove colour in boiling ethanol
- wash the ethanol off in cold water
- put the iodine solution on the leaf.
- if it goes blue/black then it contains starch.
sucrose
a disaccharide (two glucose molecules put together) that is the main sugar in the phloem.
cellulose
a polysaccharide (glucose molecules put together) that forms cell walls
what anions do plants get out of the soil
nitrates (NO3 -)
sulfates (SO4 2-)
phosphates (PO4 3-)
what cations do plants get out of the soil
calcium (Ca 2+)
magnesium (Mg 2+)
potassium (K +)
iron (Fe 3+)
uses of nitrates in bean plants
enzymes
DNA
proteins
nitrate deficiency effects
slow growth
older leaves turn yellow
uses of magnesium in bean plants
chlorophyll
magnesium deficiency in bean plants
leaves turn yellow
hydroponics definition
the growing of a plant’s roots in a plastic tube that has a mineral solution in it e.g lettuce or cannabis
what are xylem vessels
long hollow tubes made of dead cells arranged end to end forming a continuous channel
what are the holes in the walls of the xylem vessel called
pits
what does the xylem vessel contain in its cell wall that adapts it for its function
lignin
what does lignin do within a xylem vessel
it makes it structurally strong and imperable to water (waterproof)
is the xylem vessel wide or narrow
narrow
why is the xylem vessel narrow
so that water can be easily transported upwards by capillary action
what are phloem vessels
vessels that run alongside the xylem tissue
what are phloem vessels made of
specialized and nucleate parenchyma cells
sieve tube cells
companion cells
what is the function of phloem vessels
transport nutrients such as glucose and amino acids.
what direction does phloem carry nutrients
upwards and downwards. the materials are synthesized in the leaves by photosynthesis and moved to other cells of the plant
where is the nucleus in the phloem
in the companion cell
what are the phloems activities controlled by
companion cells
do companion cells have a nucleus
yes
what do roots absorb
water and minerals
water absorption is mainly carried out by
root hairs
what do root hairs increase
the surface area where water absorption can take place
how does water enter a plant (the two pathways)
apoplastic pathway
symplastic pathway
what is the apoplastic pathway
when water and minerals move from cell to cell through the spaces between the cell walls
what is the symplastic pathway
the water and minerals move across the cytoplasm to reach the xylem
do xylem vessels contain any living material
no, only water and soluble mineral salts
how much of the plant’s water is lost through the stomata
about 95%
the loss of water from roots to cells then through the stomata is called
transpiration
is the number of stomata higher on the top of leaves or the bottom
the bottom
what is transpiration caused by
the opening of the stomata controlled by guard cells on either side
how do the guard cells control the opoening or closing of the stomata
during the day, water and potassium ions go into the guard cells, increasing the turgidity and the stoma changes shape to allow water out. at night the water and potassium ions leave, decreasing turgidity and the stoma closes.
what do plants use the oxygen and carbon dioxide that enters the plant through the stomata for
photosyntheisis
osmosis definition
the movement of water down a concentration gradient of water through a partially permeable membrane.
what is transpiration
the evaporation of water from the surface of a plant.
what is transpiration affected by
changes in humidity, wind speed, temperature and light intensity.
what is diffusion
the movement of solute molecules down a concentration gradient from a region of higher concentration of solute to a region of lower concentration.
when does osmosis take place
when two solutions are separated by a partially permeable membrane.
what is osmolality
the number of particles of solute per kg of solvent.
what is osmolarity
the number of particles of solute per litre of solution.
water potential definition
how free the water molecules are to move
e.g pure water has the highest water potential
if a solution is extremely salty does it have high or low water potential
low
what does hypertonic mean
the solution is too salty/full of solute
what does isotonic mean
when the osmolality of the solution is the same in the cell and the surrounding liquid
what does hypotonic mean
the solution is too watery
what happens if you put a plant cell in a hypertonic solution
the cell releases water and shrivels up inside
turgor
the pressure inside the cell
turgidity definition
high pressure and stiff
flaccid definition
low pressure and wilting
how does the root absorb mineral ions
active transport against the concentration gradient
how does the root absorb water
through osmosis (passive)
transpiration process
water absorbed by roots
transported by xylem into leaf
in the spongy mesophyll it diffuses into water vapour and is in the air spaces
evaporates out of the leaf due to the concentration gradient
what is the transpiration stream
the flow of water from the soil to the root up the xylem to the leaves and out through the stoma
benefits of a transpiration stream to the plant
all parts of the plant receive water
all cells remain turgid (which decreases wilting and keeps the stoma open which allows more CO2 in and the plant can make more food)
mineral ions are carried up with the water
evaporation from the leaves keeps them cool
what is the phloem’s structure
cells stacked on top of eachother
what are the points of the sieve plates in the phloem’s cell walls
it allows for the sucrose/amino acids etc to pass through easier from cell to cell
do phloem cells have a nucleus
no
what are phloem cells controlled by
the cells next to them (companion cells)
what is the structure of a stem (outside to inside)
epidermis cortex a ring of many vascular bundles (the xylem and phloem are together in a vascular bundle) Central pith / dead woody lignin
what does vascular mean
a vessel
why are more stomata found on the bottom of the leaf and not the top
it would lose too much water if they were on the top
why do guard cells close at night
they have chloroplasts (which can detect when there isn’t any sun) and close the stoma.
what do the guard cells use the energy captured by the sun by chloroplasts for
to actively transport solutes (and therefore water follows) inside and remain turgid and allow the stoma to open
factors that increase rate of transpiration
more sunlight
more temperature
higher humidity
higher wind levels
what is a potometer
system of measuring rate of transpiration
types of potometer
weight
water volume
what is phototropism
responses to the stimulus of light
what is geotropism
responses to the force of gravity
what is a coleoptile
a small cereal shoot
how are auxins affected by gravity
they drop down the lower side of a plant
how do roots and shoots differ in their respone to auxins and geotropism
it will inhibit growth in a root causing it to be positively geotropic and cause growth in a plant stem causing it to be negatively geotropic
stems have a negative …
geotropic response
roots have a positive …
geotropic response
stems have a positive …
phototropic response
roots have a negative …
phototropic response
what is the growth response to the stimulus water called
hydrotropism
what is the stimulus for growth which brings about tropic responses to unidirectional light that is a water - soluble chemical produced in the growing tip
auxins
what happens to the distribution of auxins when unidirectional light hits a stem
auxins build up on the dark side of the shoot
how can you show that chlorophyll is needed in photosynthesis
use a variegated leaf and draw a pattern of chlorophyll then kill in boiling water, boil in ethanol, rinse in water, and test the leaf for starch using iodine solution. (although products of photosynthesis may have been moved from one part of the leaf to another so this is of limited use.
how can you show that carbon dioxide is used in photosynthesis
remove carbon dioxide from the air around the plant using soda lime. (although carbon dioxide is made in respiration so this is of limited use.)
how is the structure of a leaf adapted for its role as the organ of photosyntheisis
thin and flat (for a lot of light absorption and distances for gases to travel are very short)
contain chloroplasts and chlorophyll (especially in the upper palisade cells as more light is received there)
guard cells (more on lower surface to control stomata size)
xylem
spongy mesophyll tissue
large surface area
upper epidermis transparent to let light through
why do leaves have a large surface area
to absorb as much sunlight as possible
why are leaves thin
to minimise distance CO2 has to travel
why do leaves contain chloroplasts
to trap sunlight used in photosynthesis
why do leaves contain guard cells
to control the opening and closing of the stomata
why is spongy mesophyll packed loosely in a leaf
for efficent gas exchange. in photosynthesis, CO2 can diffuse in and O2 can diffuse out
describe how one named mineral ion helps plants to grow
nitrates because they make amino acids which are built up into proteins
how does temperature affect the rate of photosynthesis
the higher the temperature, the higher the rate of photosynthesis until 37 degrees.
how does light intensity affect the rate of photosynthesis
drives reactions of photosynthesis so increases it
how does carbon dioxide affect the rate of photosynthesis
more available, more photosynthesis
how would high temperatures reduce growth of plants
enzymes denature
more wilting, cells would become less turgid and more flaccid
less CO2 uptake
more transpiration - water deficit and excess water unable to leave plant
how does the upper epidermis help the leaf in photosynthesis
lets light through
is transparent
how do the palisade cells help the leaf in photosynthesis
they’re densely packed and contain lots of chloroplasts to trap light
how does the spongy mesophyll layer help the leaf in photosynthesis
air spaces allow diffusion of gases to leave and enter the cell
it transports water for hydration and removal of water
how do guard cells help the plant in photosynthesis
they open and close the stomata to let CO2 in and water out
why are the stomata found on the bottom of leaves
it allows transpiration and evaporation but doesn’t remove too much water.
what happens when a cell is placed in a dilute solution
it absorbs water by osmosis and becomes turgid
what happens when a cell is placed in a concentrated solution
it loses water by osmosis and becomes flaccid
what does a cell become when it loses excessive water through being placed in a very salty solution
plasmolyzed
where does osmosis take place
across a selectively permeable membrane,
down a water potential gradient
why do you use red onion when testing osmosis
it doesn’t need to be stained or dyed
what could increase rate of water loss
temperature
wind speed
low humidity
what could decrease rate of water loss
humidity
light intensity
spines/hairs
washing line experiment
to demonstrate tht the majority of water lost from leaves will be through the stomata. the vaseline will block the pores, so the change in mass will show where and how much water is lost
for the washing line experiment, why should you calculate the change in mass per cm squared
to compare the leaves accurately as they will not all be the same size
what indicator do you use to measure the concentration of carbon dioxide
hydrogen carbonate indicator
what colour will hydrogen carbonate indicator go in a solution with no light and what does this mean
it will go yellow as there is more CO2 due to no photosynthesis and continued respiration.
what colour will hydrogen carbonate indicator go in a solution with light
purple/red because there is less CO2 due to it being used in photosynthesis and respiration.
what colour will hydrogen carbonate indicator go in a solution with equal levels of resiration and photosyntheisis
pink because CO2 in = CO2 out
name the two parts of the cell where most water is found
cytoplasm and vacuole
how is the structure of the root hair cell adapted to absorb water from the soil
it has a large surface area and a permeable membrane
what does boiling a leaf in water do
makes cell membranes permeable and prevent any starch digestion by denaturing enzymes
how does adding boiling ethanol remove colour
it removes the chlorophyll as chlorophyll is soluble in ethanol
what is the molecule that makes leaves green
chlorophyll
what happens to a leaf when its destarched
the starch is removed
it is converted to glucose for respiration or energy
what affects rate of photosynthesis
carbon dioxide conc
light intensity
temperature
what is glucose converted to to be carried round the plant
sucrose
what is glucose stored as
starch
how do you start with a destarched plant
leave it in the dark for 24 hours
what is the glucose made in photosynthesis used for
sucrose for transport starch for storage cellulose for cell walls proteins and DNA lipids as an energy store in seeds chlorophyll
how would you show that photosynthesis is taking place in the presence of oxygen
use an aquatic plant, capture the gas produced and analyse it to show raised oxygen levels, or simply count the number of gas bubbles given off.
why do plant cells need to be turgid
to support the plant
what is transported by the xylem
water and mineral ions
what is transported by the phloem
sucrose ans amino acids
what is the xylem made up of
the cell walls of dead cells.
what is the phloem made up of
Living cells.
directional stimuli
they act in a particular direction
what is a clinostat
a piece of apparatus consisting of an electric motor turning a cork disc. germinating seeds are attached to the disc, and the motor turns it so that the movement eliminates the effect of any directional stimulus that may be acting on the seeds.
what can a clinostat be used to show
tropisms
do plants produce gametes
no YES??
do plants have fertilisation that takes place
no YES??
do plants have genetic variation in their offspring
no
what type of survival value do plant offspring have
only in a stable environment
what type of survival value do animal offspring have
in a (stable and) changing environment
what is a cutting
a form of plant reproduction, where a piece of a healthy plants stem with a few leaves attached is inserted into the soil. it will grow and develop into a new plant
male gametes in a plant
pollen grains
female gametes in a plant
egg/ova
how are male gametes transferred to a females gametes in plants
pollination
how is pollenation carried out in plants
wind or insects
what does a plant zygote develop into
a seed which becomes enclosed in a fruit
how are plant gametes produced
meiosis
where are pollen grains produced
anthers of the stamens
where are the eggs produced in a plant
ovules in the ocaries
if pollen grains are transferred from the anthers of a flower to the stigma of the same plant what is it called
self-pollination.
if pollen grains are transferred from the anthers of a flower to the stigma of a different plant what is it called
cross-pollination
position of stamens in an insect-pollinated flower
enclosed within flower so that insect must make contact
position of stigma in an insect-pollinated flower
enclosed within flower so that insect must make contact
type of stigma in an insect-pollinated flower
sticky so pollen grains attach from insects
size of petals in an insect-pollinated flower
large to attract insects
colour of petals in an insect-pollinated flower
brightly coloured to attract insects
nectaries in an insect-pollinated flower
present - they produce nectar, a sweet liquid containing sugars as a reward for insects
pollen grains in an insect-pollinated flower
larger, sticky grains or grains with hooks to stick to insects bodies
position of stamens in a wind-pollinated flower
exposed so that wind can easily blow pollen away
position of stigma in a wind-pollinated flower
exposed to catch pollen blowing in the wind
type of stigma in a wind-pollinated flower
feathery, to catch pollen grains blowing in the wind
size of petals in a wind-pollinated flower
small
colour of petals in a wind-pollinated flower
not brightly coloured, usually green
nectaries in a wind-pollinated flower
absent
pollen grains in a wind-pollinated flower
smaller, smooth, inflated grains to carry in the wind
how does the nucleus of the pollen grain fuse with the nucelus of the ovum
the pollen grain forms a pollen tube, which grows down to through the tissue of the style and into the ovary. here it curves around to enter the opening in an ovule. the tip of the tube dissolves and allows the pollen grain nucleus to move out of the tube and into the ovule
stages that lead the fertilised ovule to becoming a seed/fruit
zygote develops into an embryonic plant with a small root (radicle) and shoot (plumule)
other contents of the ovule evelop into a food store
ovule wall becomes the seed coat or testa
ovary wall becomes the fruit coat; this can take many forms depending on the type of fruit.
germination
the food store is used up, providing the nutrients to allow the root (radicle) and shoot (plumule) to grow. the radicle grows downwards to get mineral ions and water, and the plumule grows up towards the light where it can start process of photosynthesis. once it can photosynthesise, germination is over.
what conditions does germination require
warm temperatures for efficent enzymes
water for chemical reactions
oxygen for respiration
practical investigating conditions needed for germination
4 tubes, A with wet cotton wool, B with dry cotton wool, C with oil and boiled water and D with wet cotton wool. they all contain seeds. A, B and C are maintained at room temp (20 degrees). D is placed in a refrigerator at 4 degrees. after a few days A will start to germinate. B and C will not. D will eventually.
what do plants supply animals with
food, oxygen and they remove carbond dioxide
when is photosynthesis carried out at a higher rate than respiration
when light intensity is high
when is the only time a plant produces more carbon disoxide than it uses up
when it is in dim light
describe carbon dioxide levels for a plant in bright light
there is an overall uptake of carbon dioxide from the air around a plant’s leaves, and a surplus production of oxygen that animals can use.
when is carbon dioxide levels around plants highest
at night when no photosynthesis is occurring
when is carbon dioxide around plants lowest
during the day when photoynthesis is happening at the highest rate
what is hydrogen carbonate indicator used for
testing carbon dioxide conc
what colour is hydrogen carbonate indicator in high conc of CO2 (>0.04%)
yellow
what colour is hydrogen carbonate indicator in normal conc/air of CO2 (0.04%)
orange
what colour is hydrogen carbonate indicator in low conc of CO2 (<0.04%)
purple
which areas of a root hair cell are the main sites for water absorption
the root hairs (as they greatly increase SA)
what is each hair of a root cell
a single, specialsied vell of the root epiermis.
where is the water potential the highest in a root cell and its surroundings
in the soil.
how do the roots absorb water from the soil
via osmosis as the soil has a higher water potential. water then moves out of the root hair cell to the outer tissue of the root (root cortex) and a gradient of water potential is set up, kept going by water being taken up the xylem in the middle of the root.
pathway of water in the structure of the laf
up the xylem, in the leaf mesophyll. then evaporates into the air spaces between the spongy mesophyll cells. the water vapour then diffuses out through the stomatal pores.
how is there a water potential gradient within the leaf
loss of water from the mesophyll draws water by osmosis from surrounding mesophyll cells. in turn, the xylem vessels supply the leaf mesophyll tissues with water.
whatis the loss of water vapour from the leaves called.
transpiration
what does transpiration cause
water to be pulled up the xylem in the stem and roots in a continuous flow known as the transpiration stream.
functions of the transpirations stream
supplies water for the leaf cells to carry out photosynthesis
carries mineral ions dissolved in the water
provides water to keep the plant cells turgid
allows evaporation from the leaf surface, which cools the leaf, in a similar way to sweat cooling the human skin.
why are there less stomata on the lower surface of leaves than upper
if they were mainly on the upper, the leaf would lose too much water. this is because the stomata would be exposed to direct sunlight, which would produce a high rate of evaporation from them. there is also less air movement on the underside of leaves.
how do the guard cells open and close the stomata
during the day, water flows inside, and they swell up and become turgid. they bend outwards.
during the night, the guard cells become flaccid and lose this shape and the stoma closes.
factors affecting rate of transpiration
light intensity
temperature
humidity
wind speed
light intensity limiting factor
the rate of transpiration increases in the light, because of the opening of the stomata in the leaves, so that the leaf can photosynthesise.
temperature limiting factor
high temperatures increase the rate of transpiration by increasing the rate of evaporation of water from the mesophyll cells.
humidity limiting factor
when the air around the plant is humid, this reduces the diffusion gradient between the air spaces in the leaf and the external air. the rate of transpiration therefore decreases in humid air and speeds up in dry air
wind speed limiting factor
the rate of transpiration increases with faster air movements across the surface of the leaf. the moving air removes any water vapour which might remain near the stomata. the moist air would otherwise reduce the diffusion gradient and slow down diffusion.
what is a potometer
measures rate of transpiration or the rate if uptajke of water by a plant
two types of potometers
weight
volume
what does a weight potometer measure
the rate of loss of mass from a potted plant or leafy shoot over an extended period of time, ususally several hours.
what does the polythyrene bag around the pot do
prevent loss of moisture by evaporation from the soil.
what does the volume potometer do
magnifies the uptake in a capillary tube. the sumplest is a straight vertical tube joined to the shoot by a piece of rubber tubing.
what are factors you could change when investigating effects of factors on the rate of transpiration using a simple potometer
using a fan or hair dryer to investifate the effect of moving air
placing the plant under a bright light to investigate the effect of changing light intensity
