View mindmap
  • Phloem
    • Function
      • Transport sugars from one part of the plant to another, up or down the stem
    • Phloem Components
      • Sieve Tube Elements
        • Contain little cytoplasm and no nucleus
        • Lined up end-to-end to form a tube where sugars can be transported
          • Typically sucrose
            • Sucrose is dissolved in water to form sap
          • Unlike xylem, this tube contains cross-walls at intervals
            • These cross walls are perforated by pores to allow the sap to flow
              • Hence cross walls are called sieve plates and tubes are called sieve tubes
                • Sieve tubes have thin walls and are normally 5 or 6 sided
      • Companion Cells
        • In between sieve tubes with large nucleus' and dense cytoplasm
        • Have numerous mitochondria to produce ATP in active transport
          • Active transport used to load sucrose into sieve tubes
        • Cytoplasm and sieve tube elements are linked through many plasmodesmata (gaps in cell walls allowing communication and flow of substances between cells)


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Human, animal and plant physiology resources »