Vascular tissue
Vascular tissue is an essential component of higher plants, enabling them to transport water, nutrients and organic compounds throughout their structure, supporting growth and survival. This specialised tissue system consists primarily of two main types: xylem and phloem. Xylem is responsible for the conduction of water and minerals from the roots to other parts of the plant, providing structural support due to its lignified cells. Phloem, in contrast, distributes the products of photosynthesis, such as sugars, from the leaves to growing tissues and storage organs.
Xylem
Xylem consists of hollow, tube-like structures made of dead cells, such as tracheids and vessel elements, which are lignified to provide both structural support and efficient transport of water and dissolved minerals from the roots upwards. The thick, rigid walls of xylem vessels allow them to withstand the pressure of water movement, helping maintain the plant’s structural integrity while facilitating the upward, unidirectional flow of water.
Phloem
Phloem, in contrast, is composed of living cells, including sieve tube elements and companion cells, specifically adapted for transporting organic nutrients, particularly sugars produced during photosynthesis, from the leaves (source) to other parts of the plant (sinks) such as roots, stems and growing tissues. Phloem cells have thinner, non-lignified walls, utiliising them for nutrient transport rather than support. The bidirectional flow in phloem ensures that sugars reach all growing tissues and storage organs.
