Adaptations of Xylem Vessels (DP IB Biology: SL): Revision Note

Adaptations of Xylem Vessels

• The transport of water occurs in xylem vessels, one of the vascular tissues found within plants

  • Along with water, xylem vessels are also responsible for the transport of mineral ions from the roots

• The cohesive property of water, together with the structure of the xylem vessels, allows water to be transported under tension from the soil to the leaves

Xylem vessel adaptations

• Xylem vessels are formed from long lines of cells that are connected at each end

  • Mature xylem vessels are non-living cells

• As the xylem cells develop the cell walls between the connected cells degrade and the cell contents are broken down

  • This forms mature xylem vessels that are long, continuous, hollow tubes that lack cell content and end walls

  • This allows for unimpeded flow through the xylem vessels

• The walls of xylem vessels are thickened with cellulose and strengthened with a polymer called lignin

  • This means xylem vessels are extremely tough and can withstand very low internal pressures, i.e. negative pressure (tension), without collapsing in on themselves

• Xylem vessel walls contain tiny pores called pits which allow water to enter and move sideways between vessels

  • This means that if a vessel is damaged, the water can flow into another vessel and still reach the leaves

Xylem structure diagram

Xylem vessels are adapted to transport water from the roots to the leaves in plants