Component 3.2 - Distribution of vascular tissue Flashcards
Describe the structure of the xylem in the roots
In roots, the xylem is central and star-shaped with phloem between groups of xylem cells.
Why are the xylem and phloem arranges the way they are in the root?
It resists vertical stress (pull) and anchors the plant in the soil
Describe the arrangement of tissues in the stem of a plant
The vascular bundles are in a ring at the periphery, with xylem towards the centre and phloem towards the outside .
Why are the xylem and phloem arranges the way they are in the stem?
This gives flexible support and resists bending
How are tracheids adapted to their function?
Their cell walls contain lignin, which is hard, strong and waterproof.
How does water travel through tracheids?
The walls have gaps, called pits, through which the water travels.
Tracheids are spindle-shaped so water takes a twisting rather than a straight path up the plant.
What plants do tracheids occur in?
Ferns, conifers and angiosperms (flowering plants)
Why can mosses not grow as tall as other plants?
They have no water-conducting tissue and are therefore poorer at transporting water.
What are the two types of conducting cell in the xylem?
Tracheids and vessels
What are the two main functions of the xylem?
1) Transport of water and dissolved minerals
2) Providing mechanical strength and support
What conducting tissue only occurs in angiosperms?
Vessels
How do vessels get the shape of a long hollow tube?
As lignin builds up in their cell walls, the contents die, leaving an empty space, the lumen. As the tissue develops, the end walls of the cells break down.
How does water climb in vessels?
Due to it having a long hollow fine, like a drainpipe, water climbs straight up the plant.
Why are angiosperms the most dominant plant on earth?
Water moving through vessels is so much more efficient than the twisting path through tracheids.
How do you identify xylem in microscope sections?
Unlike cellulose of phloem cell walls, the lignin in the xylem stains red.
