plant transport (brain exercise!) Flashcards
this is information i did not recall in my mindblurting of the topic.
state a way that leaves are adapted for gas exchange?
leaves thin = short diffusion distance.
why do plants have a lower demand for oxygen than animals?
because they have a lower metabolic rate
is parenchyma living or non living? how do we know?
living - has a nucleus!
what is the function of parenchyma
packaging tissue - for storage and support
difference between xylem and phloem walls
xylem has no end walls, whereas phloem is divided into sieve tube elements with sieve plates.
why is it beneficial that xylem has no end walls?
to allow continuous column of water during transpiration
function of the xylem other than transport of water and mineral ions?
mechanical support for stems, roots, and leaves (due to lignin)
why is lignin beneficial to xylem walls?
adds strength and rigidity - prevents collapse under tension/transpiration pull forces
why is it beneficial that the xylem is narrow?
to ensure column of water doesn’t break
what is the function of the non lignified pits in the xylem walls?
to allow lateral flow of water
why is the cytoplasm pushed to the sides in sieve tube elements?
becomes a thin layer SO less resistance to flow
what are amyloplasts?
starch grains
function of sieve plate
keeps tubes open ( for support ) and allows tube to be blocked incase of infection
what is function of callose?
prevents loss of sap + spread of infection
if a phloem is cut, how do the sieve tube elements react?
rapidly block the sieve pores so sucrose accumulates above where it is cut (swelling)
what are cytoplasmic strands and what is their function?
- connect companion cell with sieve tube element
- facilitate movement of substances between cells (sucrose)
- enable cell signalling
what can cambium produce?
new xylem + phloem cells
function of collenchyma
extra support
state order of the layers of ‘chyma’ starting from inwards to outwards of a stem
-sclerenchyma
-parenchyma
-collenchyma
features of meristematic cells (4)
- thin cell walls
- little cellulose
- no vacuole
- no chloroplasts
what 3 organelles do phloem sieve tubes not have?
- ribosomes
- vacuole
- golgi
definition of mass flow
bulk transport of material from one point to another as a result of pressure differences between two points
why do root hair cells have short diffusion distances?
hair was thin surface layer
how can root hair cells carry out active transport of minerals
have many mitochondria to provide ATP
how do minerals move from soil to roots?
pumped in via active transport
what wall blocks apoplast pathway of water?
casparian strip (suberin)
active pumping of mineral ions causes…
root pressure
what is another term for capillary action?
cohesion-tension hypothesis
how does water availability affect transpiration
cells surrounding stomata lose turgidity so stomata may close to prevent water loss
state how number of leaves affect transpiration
more leaves = more stomata to lose water water from therefore increase transpiration
how does presence of cuticle affect water loos? (transpiration)
the thicker the cuticle the slower the rate of transpiration. (thicker leaves in younger + shaded plants)
what safety procedures must be taken into account when using a potometer?
- glass tubing
- secateurs (sharp)
- allergies (wear gloves)
in a potometer test, why must you put vaseline on the joints?
to make the leaf airtight + watertight
why must you leave the potometer experiment set up for a good 5 minutes before you start recording
to allow plant to acclimatise
why is it advantageous that cacti have spines instead of leaves?
reduces surface area for water loss
explain the adaptation of stomata in cacti?
they close at the hottest times when transpiration would be highest in order to retain water
function of the hairs on marram grass
to trap humid air to decrease water potential
why are pits in marram grass adapted to have sunken stomata?
shelters from wind + traps moist air = decreasing water potential gradient = slower transpiration
why do marram grass have rolled leaves? (3)
-minimise surface area of moist tissue exposed to air
-protects leaves from wind
-funnel rainwater to the roots
what does a xerophyte have that a hydrophyte lacks?
waxy cuticle is absent
what is the function of aerenchyma (airspaces) in a hydrophyte?
males leaves buoyant = float to surface for light
hydrophytes are wide and flat - how is this beneficial for photosynthesis?
increases surface area = more light captured = increasing gas exchange.
list the three features that reduces loss of water vapour in xerophytic leaves
- hair leaves
- rolled/curled up
- thick waxy cuticle
definition of translocation
movement of dissolved substances (solute) like sucrose and amino acids to where they are needed in a plant
what molecule is soluble and metabolically inactive?
sucrose
name the 3 stages of translocation
- phloem loading (active)
- mass flow (passive)
- phloem unloading
in active loading, how do protons move through the cell surface membrane of a companion cell?
proton pump (active)
what happens during mass flow
bulk transport of sucrose and amino acids down pressure gradient from source to sink
what happens during phloem unloading
sucrose -> moves into sink cells and is used up
what process supplies energy to pump H ions out of companion cells?
ATP hydrolysis
sucrose and H ions are transported by co-transporter protein via which process?
facilitated diffusion
how does sucrose diffuse into sieve tube elements?
via the plasmodesmata
effects of cyanide on plants
poisons mitochondria = no energy = no active loading of sucrose = no translocation
what is sucrose used for at the sink end?
converted into glucose for respiration or storage of starch
how is mass flow maintained?
decrease hydrostatic pressure at sink allows pressure gradient for mass flow to be maintained
why is concentration gradient for sucrose being maintained?
because its constantly being used up by sink cells.
