bio chap 9 - nutrition and transport in flowering plants Flashcards
what are the 3 external features of a leaf?
leaf blade
network of veins
leaf stalk
what is the function of the leaf blade
it has large flat surface compared to its volume, enabling it to obtain the maximum amount of light for photosynthesis
it is large and thin so that co2 can he produced rapidly reach the inner cells of the leaf
what is the function of the network of veins in leaves?
veins carry water and mineral salts to the cell in the leaf blade
carry manufactured food from these cells to other parts of the plant
what is the function of the leaf stalk?
holds leaf blade away from the stem so that it can obtain sufficient light and air
name the 6 parts of the internak structure of the leaf
upper epidermis
palisade mesophyll & spongy mesophyll
lower epidermis
cuticle
stomatal pore
guard cell
what are the characteristics of the upper epidermis?
it is made up of a single layer of closely packed cells
covered on the outside by a waxy and transparent cuticle
what is the mesophyll?
contains 2 types of tissue - palisade mesophyll and spongy mesophyll
main site of photosynthesis
what are the characteristics of the palisade mesophyll
consists of half layers of closely packed long and cylindrical cells
contains numerous chloroplasts
what is the function if the palisade mesophyll
main site for photosynthesis
what are the characteristics of spongy mesophyll?
contains irregularly shaped cells
numerous large intercellular air spaces among the loosely packed cells
cells covered with a thin film of moisture
contains transport tissues (xylem amd phloem) grouped together forming vascular bundle
what is the function of the spongy mesophyll
carries out photosynthesis
but has fewer chloroplasts than the palisade mesophyll
what are the characteristics of the lower epidermis
consists of a single layer of closely packed cells
what are the characteristics and function of the cuticle?
cells are covered by an outer layer of cuticle
reduces water loss through epidermal cells
what are the characteristics of the stoma/stomatal pore?
many minute openings called stomata
what are the characteristics and function of a guard cell?
contains chlorophyll, not present in any other epidermal cells
a pair surrounds each stoma and helps to regulate the rate of transpiration by opening and closing the stoma
what are the 6 adaptations of the leaf to carry out photosynthesis
waxy cuticle on upper/lower epidermis
stomata ptrsent in epidermal layers
chloroplasts containing chlorophyll in all mesophyll cells
more chloroplasts in upper palisade tissue
interconnecting system of air spaces in spongy mesophyll
veins containing xylem and phloem situation close to mesophyll cells
what is the function of this adaptation of the leaf
waxy cuticle on upper/lower epidermis
reduces water loss through evaporation from the leaf
transparent so that light can enter the leaf
what is the function of this adaptation of the leaf
stomata present in epidermal layers
stomata open in presence of light causing co2 to diffuse in and o2 out of the leaf
what is the function of this adaptation of the leaf
chloroplasts containing chlorophyll in all mesophyll cells
chlorophyll absorbs energy from light
transfers it to chemical stores of energy in glucose molecules
what is the function of this adaptation of the leaf
more chloroplasts in upper palisade tissue
more light absorbed near upper leaf structure
what is the function of this adaptation of the leaf
interconnecting system of air spacew in spongy mesophyll
allow rapid diffusion of co2 and o2 into and out of mesophyll
what is the function of this adaptation of the leaf
veins containing xylem and phloem situated close to mesophyll cells
xylem transports wayer and mineral salts to mesophyll
phloem transports sucrose away from the leaf
how do guard cells control the size of stomata
stomata opens in light and closes in dark
guard cells help to regulate the passage of gases between the leaf anf environment
explain how guard cells control the opening of stoma
guard cells manufacture glucose by photosynthesis as
increase in glucose concentration decreases water potential of cell sap on the cell
water enters guard cells via osmosis
guard cells become turgid and more curved as
cell wall around stoma is thicker than other parts of the cell causing it to curve around the stoma, and the stoma opens
explain how the guard cells control the closing of the stoma
when the leaf loses too much water, the stomata close as
excess evaporation causes guard cells to become flaccid
this prevents excessive water loss by the leaf
how does carbon dioxide enter the leaf through the stomata?
in the daylight, photosynthesis occurs
carbon dioxide in leaf is rapidly used up
co2 conc in leaf is lower than in the atmospheric air causing a diffusion gradient to exist
this causes co2 to diffuse from the surrounding air through stomata into intercellular air spaces in the leaf
surfaces of mesophyll cells are always covered by a thin film of water so that co2 can dissolve in it
dissolved co2 diffuses into cells
how does the xylem transport water and mineral salts to the leaf?
the xylem transportd water and dissolved mineral salts to the leaf from the roots
once out the veins, water and mineral salts move from cell to cell through mesophyll and lewf
what happens after the xylem transports water and mineral salts to the leaf?
once the green cells receive the essential raw materials such as co2 and h2o, it manufactures food by photosynthesis
phloem transports sugars made in the leaf to other parts of the plant
what are the characteristics and function of the xylem?
conducts water and dissolved mineral salts from the roots to the stems and leaves
provides mechanical support for the plant
xylem tissue consists mainly of xylem vessels made up of many dead cells
explain the adaptations of the xylem
empty lumen
the xylem has an empty lumen without cytoplasm or cross walls
-> xylem vessels form a long hollow continuous tube which stretches from root to leaf
-> lack of cross walls in the xylem vessels reduce resistance to water flowing through the xylem
explain the adaptations of the xylem
lignin
inner walls of xylem vessels are strengthened by deposits of lignin
it is a hard and rigid substance that prevents collapsing of the vessel
explain the adaptations of the xylem
mechanical support
all xylem vessels provide mechanical support to the whole plant
lignin is deposited in the form of rings or the whole vessel may be lignified except in the regions called pits
what are the characteristics and functions of the phloem
conducts manufactured food substances (glucose and amino acids) from the green parts of the plant to other parts of the plant
consists mainly of long tubes made up of a row of living cells
explain the adaptation of the phloem
each tube stretches form the leaf to other parts of the plant
the cross walls separating the cells have a lot of minute pores
this allows rapid flow of manufactured food substances through the tube
how are the vascular tissues organised in stems
within a vascular bundle, the xulem is located closer inside
the phloem lies outside the xylem with a tissue called the cambium between them
the stem is covered by a layer of celle called the epidermis
epidermal cells are protected by a waxy and waterproof cuticle and reduces the evaporation of water from the stem
where are the xylem and phloem located in the leaf
xylem is closer to upper surface of the leaf
phloem is closer to the lower surface of the leaf
what is photosynthesis
the process where chlorophyll absorbs the energy from light to make glucose from co2 and water and releases o2
what is the word equation for photosynthesis
co2 +h2o -> (light up, chlorophyll down) glucose + oxygen
how does light intensity affect photosynthesis
when light intensity increases the rate of photosynthesis increases
because more light is supplied to the plant causing an increase in the amount of energy that can be used for photosynthesis
after a certain point, rate of photosynthesis remains constant even when light intensity increases
how does carbon dioxide concentration affect the rate of photosynthesis
when the conc of co2 increases, the rate of photosynthesis increases
because more co2 is available for the plant to carry out photosynthesis and produce more glucose
after a certain point the rate of photosynthesis remains constant evej when co2 conc increases
how does temperature affect the rate of photosynthesis?
when temperature increases to optimum temperature, the rate of photosynthesis increases
beyond the optimum temperature, the rate of photosynthesis decreases rapidly as enzymes involved are being denatured
how is glucose utilised in plants - leaves
used immediately in the leaves
for cellular respiration provide energy for cellular activities
forming cellulose cell walls
how is glucose utilised in the leaves - conversion between glucose and starch
conversion between glucose and starch
in daylight, excess glucose made is converted to starch for storage
in darkness, starch is converted back to glucose
how is glucose utilised in plants - conversion to sucrose
sucrose is transported to other parts kf the plant/storage organs such as seeds and root tubers
sucrose is converted into other forms of storage compounds at storage organs
sucrose may be converted back to glucose by enzymes for respiration
sucrose is a component of nectar in flowers to attract insects for pollination
how is glucose utilised in plants - converted to amino acids in leaves
amino acids form proteins needed to build protoplasm in leaves
transported to other parts of the plant for
synthesis of new protoplwsm
for storage as proteins
how is glucose utilised in plants - formation of fats
glucose is utilised to form fats
for storage
synthesis of new protoplasm
used in cellular respiration
explain the importance of photosynthesis - chemical energy
photosynthesis makes chemical energy available for organisms that cannot make their own food
during photosynthesis, chlorophyll absorbs energy from light and transfers it to chemical stores of energy in carbs
these carbs are converted to fats, proteins and other organic compounds that become food for other organisms
plants are producers in food chains and all organisms obtain chemical energy directly or indirectly from them
explain the importance of photosynthesis - removal and release of gases
photosynthesis removes co2 and release o2
o2 allows living things to carry out respiration and release energy for all cell activities
this mantains a constant level of oxygen and co2 in the atmosphere
explain the importance of photosynthesis - storing energy in fossil fuels
coals are formed from trees
when coal is burnt, energy in chemical store of coal is used to drive machinery
and transferred to other energy stores
explain the procedure of the experiment to investigate light intensity on the rate of photosynthesis
vary the distance, xcm, of light source from the plant for each investigation
a shorter distance would give a stronger light intensity
co2 conc and temp are kept constant
results are obtained by counting number or bubbles releasee per time
explain the procedure of the experiment to investigate co2 conc on the rate of photosynthesis
use different concs of xm3 of solution
sodium hydrogen carbonate is a source for co2 gas
constant factors are light intensity and co2 conc
results obtained by counting number of bubbles released per time
explain the procedure of the experiment to investigate temperature on the rate of photosynthesis
use dif temperatures, x°c of solution
constant factors are light intensity and temp
results obtained by counting number of bubbles released per time
how to study photosynthesis by testing for starch on leaf
when photosynthesis is carried out actively, glucose is formed more quickly than it is used up
causing excess glucose converted into starch for storage in the leaf
why is it that starch formation may not indicate that photosynthesis has taken place
starch can be formed in the roots/underground storage organs of plants
why must we destarch before experimenting on photosynthesis by placing plants in the dark
in darkness, no photosynthesis occurs, enzymes cannot convert starch into sucrose causing no starch to be left in the leaves
this ensures that starch is not present in leaves before experiement so that we can assume that all starch present in the leaves after experiment must have been formed during the experiment
what is translocation?
transport of food, mainly sucrose in the phloem tissue
what is the evidence to show that the transport manufactured food subsyances occurs through the phloem
a ring of bark with phloem is removed from the stem of a woody plant
after some time, the stem above the cut region swells immediately
this is because when the phloem was removed, food substances from the leaves cannot reach the stem below the cut region
food substances accumulate in the region above the cut region and swells up
explain the 5 step procedure of the entry of water into a plant
- each root hair is a narrow extemsion of epidermal cell
it grows between the soil particles, coming into close contact with surrounding soil solution - film of liquid, a dilute solution of mineral salts, surrounds each soil particle
- cell sap in the RHC is a concentrated solution of sugars and salts
hence it has a lower water potential than soil solution
cell sap and soil solution is separated by ppm of RHC
water enters root hair by osmosis - entry of water dilutes cell sap
cell sap of RHC has a higher water potential than that of the next cell
water passes by osmosis from RHC to the inner cell - water passes from the inner cell to the next cell of the cortex
process continues until the water enters xylem vessels and moves up the plant
how do root hairs absorb ions/ mineral salts
when the conc of certain ions in soil solution is higher than in the RHC, and enter the cell by diffusion
when conc of ions in soil solution is lower than in the RHC sap, energy used to absorb ions against a conc gradient
how is the root hair cell adapted to its function of absorption
RHC has a long and narrow extension
which increases the surface area to volume ratio and increases the rate of absorption of water and mineral salts
cell membrane of RHC prevents cell sap from leaking out
cell sap contains sugars, amino acids, and salts
when the cell sap’s water potential is lower than the soil solution, water enters roots by osmosis
what is transpiration
loss of water vapour from the aerial parts of a plant, mainly through the stomata of the leaves
explain the 5 steps of transpiration pull
- when water moves out the mesophyll cells, it forms a thin layer of moisture over their surfaces, then it evaporates into the intercellular air spaces
- this causes the concentration of water vapour in the intercellular air spaces to increase
and allows it to diffuse out through the stomata
this causes a loss of water vapour from the leaves / transpiration - thin film of moisture is replenised by more water moving out of mesophyll cells as it evaporates
- this causes water potential of their cell sap lesser than that of mesophyll cells deep inside the leaf
this allows water to move from the inner mesophyll cells to the thin film of moisture via osmosis - mesophyll cells deeper inside the leaf extract water from the xylem vessels via osmosis
this produces suction force that pulls water upward in the vesells, the transpiration pull
what is the importance of transpiration - transportation of water
water can be transported to leaves for photosynthesis which keep cells turgid and replace water lost by cells
turgid cells enable the leaves to spread out widely to trap light for photosynthesi
transpiration pull moves water & mineral salts up the roots to the stems and leaves
what is the importance of photosynthesis - absorb heat
a leaf exposed to direct sunlight will absorb heat
its temp might increase to a level that would kill the leaf
its water evaporating from the leaf helps cool the leaf down
how to experiment to investigate factors affecting the rate of transpiration - balance
factor: light intensity
changed factor: light intensity - place one set up in a sunny area and another in a dark room
constant variables: air humidity, wind conditions, temperature
- record initial weight of apparatus
- record final weight of the apparatus
- rate of transpiration = loss in weight/time taken
what is a potometer
an instrument used to measure the uptake of water by a plant
what is the assumption when using a potometer to investigate the rate of transpiration?
water uptake = water loss by transpiration
as some water may be used by plants for photosynthesis
how does using a potometer to investigate the rate of transpiration work
when the plant transpires, it absorbs water from the potometer to replace water loss by evaporation through the stomata
this causes water in the collumn in the capillary tube to move from x to y
how to calculate rate of transpiration using formula
a cm + t second
-> a is the length/ volume moved from x to y
-> t is time taken for air bubbles to move from x to y
what precautions should be taken when using a potometer to investigate the rate of transpiration
plant must be cut underwater to prevent air being trapped in the xylem
cut end is kept immersed in water for a few hours before use
this is to allow shoot to adjust to the conditions in the potometer
how does air temperature affect the rate of transpiration
transpiration will take place more rapidly when the surrounding temperature is higher
this is because water from leaves will evaporate more readily at higher temperatures
how does presence of wind affect the rate of transpiration
in still air, air surrounding a leaf becomes saturated with water vapour that diffuses out of it
causing less steep concentration gradient of water vapour between leaf and air
hence rate of transpiration decreases
how does light affect the rate of transpiration
light affects the size of stomata
in daylight, stomata are open
water vapour in the leaves can easily diffuse out into the atmosphere, increasing the rate of transpiration
at night, stomata close and transpiration is greatly reduced
how does humidity affect the rate of transpiration
intercellular air spaces in a leaf are usually saturated with water creating a water vapour concentration gradient between the leaf and surrounding air
the decreasing air humidity causes a lower amount of water vapour in the air
this causes a steeper concentration gradient between the leaf and the air increasing the rate of transpiration
hence water vapour can diffuse from the leaf into drier or less humid air causing a steeper concentration gradient of water vapour between the leaf and air
what are the adaptations that plants living in hot and dry environments have developed to reduce water loss
sunken stomata that lie in grooves in the upper surface of the leaves have numerous tiny hairs that trap water vapour diffusing out of the stomata
this gives rise to increasing humidity around the stomata that helps reduces rate of transpiration
what is turgor pressure
pressure exerted by the fluid, inside the cells of a plant against the cell wall
why is it important for there to be turgor pressure in the mesophyll cells
to support the leaf and keep it firm as it can spread out widely to absorb light for photosynthesis
how does a plant wilt
when rate of transpiration is more than the rate of absorption by the roots in strong light,
cells lose their turgor and become flaccid, causing the plant to wilt
what are the advantages of plants wilting
their leaves fold up to decrease surface area exposed to sunlight, decreasing exposure of stomata to the atmosphere, causing a decrease in the rate of water loss through stomata
guard cells become flaccid and close stomata lowering the rate of transpiration
what are the disadvantages of plants wilting
there is a decrease in the amount of carbon dioxide entering the leaves causing carbon dioxide to be a limiting factor that decreases the rate of photosynthesis in the plant
wilting decreases the surface area exposed to light, decreasing the rate of photosynthesis
