plant-transverse-sections

Transverse sections: stems, roots & leaves

Transport systems

• Plants need transport systems to:

  • Meet their metabolic demands (glucose, hormones, mineral ions are required for various processes within plants)

  • Efficiently move substances up and down, e.g.

    • Glucose from photosynthesis needs to be transported to parts of the plant that cannot photosynthesise

    • Water from the roots needs to be transported to the upper parts of a plant

    • Plants may store glucose in storage organs, e.g. tubers, and need to release this glucose and transport it to metabolically active parts of the plant

• Plants consist of many layers of cells and so cannot rely on diffusion from cell to cell to supply all their needs, as this would be too slow

• Plants therefore have a vascular system which involves a network of vessels (vascular tissue) running through the leaves, stem and roots

  • These three parts are the main organs involved in transport

• The vascular system is comprised of two distinct types: 

  • Xylem transports water and mineral ions from the roots to the rest of the plant

  • Phloem transports substances from the source (e.g. a leaf) to the sink (e.g. root)

• The xylem and phloem are arranged together in vascular bundles

• The bundles are laid out differently in the leaves, stem and roots