Structure and functions of phloem

https://www.youtube.com/watch?v=Ur7w9IdP8Xg

What is the job of the phloem

To transport the assimilates (sugars / amino acids produced by glucose from photosynthesis) from the leaves to other parts of the plant such as the roots or flowers/

Molecules can be moved up and down phloem , and the fluid moving in phloem is referred to as phloem sap

What is sieve tube element

Its a living tissue, consists of two different types of tissue

The sieve tube element cell - consists of a long line of cells arranged end to end, inside these cells, almost all of the organelles have been lost including nucleus and vacuole. This leaves the interior of these calls almost entirely free to transport phloem sap

Whats sieve plate

The end walls of these cells have been modified to contain large pores, these are called a sieve plate.

Sieve plates allow the phloem sap to move between the cells

What are companion cells

They are next to sieve tube element cells, companion cells contain a nucleus as well as large amounts of mitochondria.

Microscopic channels link the companion cells to the sieve tube, these are called plasmodesmata.

Molecules such as ATP and proteins can move through plasmodesmata into sieve tube element cells

So companion cells provide essential molecules to the sieve tube element cells.

What tissues do phloem include that provide support

These are called fibres and sclereids, both of these have thickened cell walls containing lignin

Fibres are long and narrow whereas schlereids have a variety of shapes,