module 3-transport in plants Flashcards
transport in plants needed for
metabolic demands
size
sav
metabolic demands
many parts of plants need o2 and glucose
need waste products to be removed
hormones needed for transpiration.
size
need effective transport to move substances up and down.
SAV
leaves adapted to have large SAV exchange
cannot rely on diffusion to supply thier cells
xylem
largely non living tissue
made of several types of cell, and most are dead when functioning.
long hollow structures made by several colums fusing.
has two tissue
long cell with secondary walls
lignin, rto support
form rings, which is boarded pits, so water can leave xylem.
what are the tissues in xylem
xylem parenchyma, which packs around the xylem vessel.
stores food.
contains tannin
functions of xylem
transport of h20 and mineral ions
flow of materials in xylem is up from roots to shoots and leaves.
what is tannin
bitter chemicals to avoid herbivores.
pholem
living tissue transporting food
supply cells with sugars and aamino acids. needed for respiration.
flow can go up or down .
not lignified.
walls form sieve plates, to allow content to flow
large pores, allow nucleus and organelles to break down
becomes tube filled with sap.
a mature pholem has no nucleus
what is main transport vessels for pholem
sieve tube elements, made from cells joined end to end, and are long and hollow
companion cells
very active cells, which have life support system so lost most normal functiobs
companion cells are closely linked to…
sieve test tubes.
these have many plasmodesmata, (microscopic channels linking cytoplasm)
maintains nucleus and all their organelles.
hydrostatic shelton
hydrostatic pressure resulting in plant cell, to support stems and leaves. divides cell expansion, enabling plant to go through tarmac.
loss of water is by evaporation.
mineral ions/photosynthesis transport.
root hair cells
exchange where water taken in.
long thin extension.
microscopic size, so pentrates easily.
root hair cells hair
thin surface layer, so diffusion and osmosis can occur.
soil water
low concentration of dissolved material, so has high water potential.
cytoplasm
many solvents, and lower water potential
movement of waters
symplast or anoplast
symplast pathway
water moves along symplast by osmosis.
symplast=continuous cytoplasm of living plant cells connected through plasmodesmata.
root hair cells, have higher water potential then next cell, so diffuses from coil to next cell, until reaches xylem.
as water leaves the root hair cells by osmosi, water potential decreases, so water completely moves from the soil.
anoplast pathway.
movement of water through cell wall and intercelluar spaces,
water fills spaces, between loose network.
water moves into xylem, more water pulled through due to choesvie forces of molecules.
pull from water moving to xylem and up plant, and creating tension, leading to flow of H2O.
movement of water from xylem
water moves across root in apoplast and symplast, until reaches endodermis, where layer of cell surrounding vasuclar tissue
endothermisis is noticable due to the casparian strip.
water in apoplast go no further, so goes to cytoplasm, and joined in symplast, as goes through permable membrane so no toxic solutes go.
casaparian strip
waxy material forming a waterproof layer.
vascular tissue
xylem and pholem
when enters vascular bund;e
water returns to apoplast pathway, so can enter xylem, so can move up.
active pumping of minerals to xylem, so water is moved by osmosis. THIS is root presusre
root pressure
independent of any effects of transpiration, and gives water a push up.
roles of active transport evidence
root pressure increases with temp increases.
levels of o2 fall, if root pressure falls.
transpiration
have to ensure gagses move in and out for photosynthsis.
co2 moves from air to leave
o2 moves out through pores=stomata, opened and closed by guard cells.
how are plants waterproof
surfaces covered with waxy cuctile, prevents cells losing water.
stomata opens?
exchange of co2 and o2 between air and leaf.
water vapour moves out and is lost. this is known as transpiration.
stomata opens/closes for
control water lost.
day opens-takes in co2
nigh closes-no need of sunlight
transpiration steam
moves by osmosis across membranes
diffusion in apoplast from xylem through cells.evaporates from permeable wall to airspaces.
water vapour move to air through stomata along diffusion gradient.
mocves water up from roots of plants to highest leaves.
transpiration steam-xylem
h2o evaporates of mesophll moving out of stomata by diffusion.
loss of water=lower water potential so move to cell by osmosis.
repeated across leafd to xylem, move by osmosis to cells.
ahension and cohesion
ahension
water molecules form h2 bonds with carbohydrates.
cohesion
water molecules form h2 bonds with each other
combination of ahesion and cohesion
exhibits capilary action, so water moves up against gravity, in a continous stream, THIS IS TRANSPIRATION PULL.
evidence of cohesion-tension theory
changing in diameters-tree shrinker when tension is highest.
xylem vessel broken, and air is pulled up, so plant dosent move
stomata
turgor driven process
environmental favourable, guard cells pump solutes by active transport-MORE TURGOR.
cellulose hoops prevent cell swelling, move lengthway.
guard cells less flexible, so leads to cell becoming bean shaped.
less water-hormonal signals, so closes pores.
turgor driven process
turgor is low-closes pore.
factors affecting transpiration
temperature
air movement
soil water availability
temperature
increases, more kinetic energy of water, so more evaporation. also more water vapour, so decreases humidity, both increasing transpiration.
air movement
each leaf has layer of still air, which has hairs decreasing movement, so water vapour accumulates here, so higher water vapour potential, so higher gradient, and more rate of transpiration.
translocation
leaves of a plant produce large amount of glucose=needed for respiration by cells.
this is converted to sucrose, and converted back.
active process-energy neede, substances moved up or down
plants transport organic..
in phloem from sources to sink.
sources
green leaves/green stems.
storage organs unloading stores.
food stores in seeds.
sinks
roots growing/absorbing minearl ions.
meristems actively dividing
laying down food stores.
pholem loading
Many plants, soluble products moved to pholem, from sources in active transport.
MAINLY surcose, as not used in metabolism.
Can be active and passive
ACTIVE pholem loading
apoplast
surcose travels through cell wall/intercell spaces, to companion cells, by diffusion.
COMPANION CELLS-surcose moved to cytoplasm across membrane.
H+ pumped out of companion cells into tissue USING ATP, and returns to companion cells down concentration gradient via proteins.
SURCOSE is cotransported, more concentration in companion cells and in sieve elements.
companion cells
many infoldings in cell membrane,MEANS higher surface area, and many mitochondria.
due to buildup of sucrose, water move by osmosis. higher turgor pressure, so water moves to sieve elements, reduces pressure in cells, so moves up/down by mass flow.
solute accumlating-source
pholem leads to increase in turgour pressure, so sap goes to sink lower pressure. PRESSURE difference, leads to transport of sources.
pholem unloading
sucrose unloaded from phloem.
can also be converted to another molecule. this maintains concentration. gradient between pholem and cells.
loss of solutes from pholem
rises in water potential, so mvoes into surrounding cells by osmosis.
some water drawn to transpiration system.
evidence of translocation
mitochondria poisioned-no translocation.
flow of sugars faster by diffusion alone.
xerophytes.
plants have adaptations to conserve water.
including:
waxy cucticle, reduces transpiration
hot conditions, water evaporates rapidly.
ways of conservation
thick waxy cucticle
sunken stomata-less air movement
less stomata
less leaves
hairy leaves
curled leaves
succleents
leaf loss
long roots
hydrophytea
need adapations to lose water.
ways of losing water
no waxy cuctile
many open stomata
no strucrure
wide flat, capture lots of light
small roots
stem root. large surface.
endoermis
layer of cells covering xylem and pholem
