transport in plants exam questions Flashcards
What is a vascular system?
system of transport vessels in animals and plants
Dicotyledonous meaning
Plants that produce seeds containing 2 cotyledons which act as food stores for developing embryo and form first leaves when the seed germinates
Potometer apparatus question
Cut healthy shoot under water
Cut at an angle
check apparatus is full of water
insert shoot into apparatus under water
dry leaves
keep condition(s) constant;
allow time for shoot to acclimatise
shut screw clip;
keep ruler fixed and record position of air bubble on scale;
start timing and, measure distance moved per unit time
Transpiration definition
Loss of water vapour through stomata
Via diffusion down the water vapour potential gradient
Features of xylem and functions
LIGNIN
stops xylem from collapsing/ waterproofs the wall and strengthens the WALL
NO CYTOPLASM
hollow so less reistance to flow
LACK OF END WALLS-
less resistance to flow
PITS-
allow lateral movement of water to bypass blockage/ supply water to other plant cells
Suggest 2 ways in which photographing the leaf surfaces makes measuring the stomata easier
1) Permanent record
2)Stomata may change size
3)Photographs can be enlarged
Why can’t transpiration be avoided?
Due to photosynthesis
Stomata open to let oxygen out and co2 in
most mesophyll to dry air so there is a water vapour potential gradient
Explain how, at different times, the same plant root may be a source or a sink
ROOT= source when it converts starch into sugars
ROOT= sink when root stores starch and use carbohydrate for respiration
high hydrostatic pressure makes it a source
low hydrostatic pressure a sink;
when loading it is a source
when unloading a sink;
How are root hairs adapted to increase uptake?
Long
Thin cell wall
large surface area
present in large numbers
many mitochondria
Definition of source and sink
SOURCE- site where assimilates are loaded
SINK-site where assimilates are removed/unloaded
Example of source
Example of sink
Source- green leaves/ storage organs(e.g. tubers)
Sink-roots that are growing/ actively dividing meristems/ seeds
Evidence for the involvement of active process in translocation
Companion cells have many mitochondria (ATP)
Loading against concentration gradient
Suggest what the student would need to do in order to get a valid comparison of the rates of transpiration of the two species.
Set up in same environmental conditions
Same area of leaf in both species
Both picked at same time
Same degree of turgidity
Xerophytes adaptations
-Covered in hairs-trap WATER VAPOUR and creates a humid environment -> reduces the wvpg
-Thick waxy cuticle- reduces the water loss
-Leaves reduced to spines-reduced surface area for water loss/ less transpiration
-sunken stomata- WATER VAPOUR trapped
-rolled upleaves-stomata on the inside/ reduces EXPOSED SA for evaportation
-Stomata shut during day-less evaporation at night as it is cooler-
Explain how transpiration results in the movement of water up a plant stem.
loss of water from mesophyll;
more drawn from, cytoplasm
cohesion of water molecules;
hydrogen bonds;
water under tension
water ‘pulled’ via, symplast / apoplast pathways
(water from) xylem / xylem vessels;
ref to water potential gradient;
