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First teaching 2023

First exams 2025

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Adaptations of Xylem Vessels (HL IB Biology)

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Marlene

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Marlene

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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 degradeĀ 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 Structure

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

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Marlene

Author: Marlene

Expertise: Biology

Marlene graduated from Stellenbosch University, South Africa, in 2002 with a degree in Biodiversity and Ecology. After completing a PGCE (Postgraduate certificate in education) in 2003 she taught high school Biology for over 10 years at various schools across South Africa before returning to Stellenbosch University in 2014 to obtain an Honours degree in Biological Sciences. With over 16 years of teaching experience, of which the past 3 years were spent teaching IGCSE and A level Biology, Marlene is passionate about Biology and making it more approachable to her students.