8. Transport in Plants Flashcards
What is the function of xylem vessels?
transport of mineral ions and water (and support for the plant)
What is the function of phloem vessels
transport of sucrose and amino acids
In a cross section of a stem, where is the xylem and phloem?
Xylem is more inwards than the phloem.
In the vein, where is the xylem and phloem?
Xylem is above the phloem.
How are xylem vessels adapted to their function?
thick walls with lignin for support, only dead cells, waterproof, long and hollow tubes made from cells joined
How is a root hair cell adapted for absorption of water and mineral ions?
it has a large surface area
What is the pathway taken by water and mineral ions in the plant?
root hair cells > root cortex cell > xylem vessel > mesophyll cells
What is transpiration?
The loss of water vapour from leaves
How does water evaporate in transpiration?
It evaporates from the mesophyll cell’s surface, into the air spaces in the spongy layer and out through the stomata
What factors increase transpiration?
light intensity, temperature and wind
What factor decreases transpiration?
humidity
How does water move up the xylem?
Via a transpiration pull that draws water molecules, attached by intermolecular forces of attraction. The plant needs a constant number of water molecules in the xylem at any given time
When do plants wilt?
When they transpire more than they absorb water
What is translocation?
The movement of sucrose and amino acids in phloem from sources to sinks
What are sources?
the regions (parts) of the plant responsible for releasing sucrose or amino acids
What are sinks?
the regions (parts) of the plant that utilise or store sucrose or amino acids
Name one plant organ that is both a source and a sink at different times.
Leaf: source when photosynthesis occurs, but sinks when they are growing.
taylor
swift
What are the functions of the xylem vessel?
support
transport water/mineral ions from roots to leaves
What is the function of the phloem vessel?
transport of amino acids and sucrose
In a vascular bundle cross section, which vessel is on top and which is on the bottom?
xylem on top
phloem on bottom
Name three adaptations found in xylem vessels.
thick walls with lignin
no cell contents (dead)
cells joined end to end, continuous tube
Why do xylem vessels have thick walls?
support, for plant to remain upright
Why do xylem cells have no cell contents?
provide space for water transport
What is the function of the root hair cell?
increase surface area of roots, to increase uptake of water and mineral ions
What is the function of the root?
absorb water and mineral ions from soil
Why does the root hair cell have a large surface area?
increase uptake of water and mineral ions
What is the pathway taken by water from root to leaf?
root hair cells -> root cortex cells -> xylem -> mesophyll cells
What is a way to investigate the pathway of water from the stem to the leaf?
chop up celery, place bottom half in dyed water and see as the leaves also stain
What is transpiration?
loss of water vapour from leaves
How does water from the surface of mesophyll cells evaporate to the surroundings?
- water evaporates from surface of mesophyll cells
- it goes into the air spaces
- leaves the plant through stomata, as water vapour, via diffusion
How does temperature affect transpiration?
the higher the temperature, the higher the transpiration rate
How does wind speed affect transpiration? How does this work?
the faster the wind speed, the higher the transpiration rate
this is because it sweeps water vapour away from leaf surface
How does number of stomata influence transpiration rate? Why?
the more stoma, the higher the transpiration rate
stoma allows water vapour to diffuse from plant; more stoma, more diffusion of water vapour
Which features allow evaporation of water from surface of mesophyll cells to be quick?
air spaces
large internal surface area
How does water move upwards in the xylem? How does this mechanism work?
it has a transpiration pull: this draws up a column of water molecules, held together by forces of attraction between the molecules
How do water molecules stay held together in a transpiration pull?
forces of attraction between molecules
Very simply, what is a transpiration pull?
suction force
What is an environmental factor that reduces transpiration rate?
humidity
What are environmental factors that increase transpiration rate?
light intensity, temperature and wind
What causes wilting?
loss of water from plant cells
How does wilting occur?
when plant cells lose more water than they gain, they lose their turgidity and become flaccid.
they can no longer stay upright and rigid and wilt
Define ‘translocation’.
the movement of sucrose and amino acids in phloem from sources to sinks
Define ‘sources’.
parts of plants that release sucrose or amino acids
Define ‘sinks’.
parts of plants that use/store sucrose or amino acids
What are two possible functions of a sink?
region of storage
region of use in respiration growth
What factor might change if a part of a plant is a source or a sink?
seasons
