Multicellular plants need transport systems due to their size, metabolic rate and surface area to volume ratio. They need to transport substances like water, nutrients, and sugars across long distances.

The vascular system in plants consists of the xylem and phloem tissues:

1. The xylem transports water and dissolved minerals from the roots to the stems and leaves
2. The phloem transports substances like sugars and amino acids from where they are made (e.g. in the leaves) to where they are needed (e.g. in the roots)

The xylem is made up of xylem vessels, which are long, continuous tube-like structures.

The phloem contains sieve tube elements and companion cells:

1. Sieve tube elements - these cells are stacked vertically to form long tubes with sieve-like structures between adjacent cells
2. Companion cells - these are specialised cells attached to sieve tube elements

Companion cells have a large number of mitochondria and ribosomes, which provide energy and proteins for the active transport of substances.

Companion cells assist the sieve tube elements in the phloem by providing energy for active transport of substances.

Mineral ions dissolve in water and are transported via the xylem in plants.