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.
What is cohesion and adhesion?
Adhesion: property of water that allows it to connect to thin walls of the xylemCohesion: property of water that keeps water molecules together like a necklace
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
