Translocation

What is translocation

The movement of something (solutes) to where they are needed

What is the source and sink?

Source = where solutes are made

Sink = where solutes are needed

T between the streams in phloem and xylem

Xylem carries water up in one way, while phloem carries water and sucrose up and down the phloem vessels

Two things that the phloem cell contains?

Sieve tube element and companion cells.

These cells work together to create a concentration gradient and to load sucrose and source and move sucrose to a sink

Phloem tube adaptations

Phloem cells have depleted cytoplasms and distorted shapes, therefore mist have companion cells to help carry out the function of the sieve tube elements.

What are companion cells and sieve tube elements?

Companion cells = living cells attached to the sieve tube elements

Sieve tube elements = permeable boundaries in phloem tubes

What suggests that is a flow of sugars against gravity?

A ring of bark is removed, cutting the phloem. A buldge of concentrated sugars forms above the ring

What suggests there is a pressure gradient?

Aphids are placed at different points on the plant. They bite the plant and then are removed. Sap flows out quicker nearer the leaves than further down the roots.