Question

1) Zip up the xylem is probably a good way to remember the movement within the xylem but flow down the phloem is not always accurate. Why not? What types of cells are found in each of these tissues and what are their roles?

2) What is the minimum number of plasma membranes a water molecules would have to cross in order to get from the soil solution to the atmosphere by way of the stele? To get from the soil solution to a mesophyll cell in a leaf?

Answer 1

1.

Phloem is present outside the concentric ring. The arrangement of phloem in monocots and dicots is also different. The food usually synthesize in the leaves and this is arrangement of phloem cells in different plants. This is the reason that flow down the phloem is always not accurate.

Cells in phloem:

Sieve tubes- help in translocation of material.

comapanion cells- they help in the survival of sieve tubes.

Phloem fibres

Phloem parenchyma cells- help in absorbing the food material.

Cells of xylem:

Tracheids- found in vascular plants and help in transport of water.

vessel elements- confined to angiosperms and transport water.