Transport in plants🤓

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  Root structure

  • Piliferous layer: contains root hairs which are thin, permeable tubular extensions of epidermal cells
  • Cortex : consists of parenchyma cells in which starch may be stored
  • Endodermis: is one cell thick and possesses an impermeable casparian strip of suberin within its cell walls
  • Phloem: Transports the products of photosynthesis, consists of living cells including sieve elements and companion cells
  • xylem: Transports water and mineral ions from the roots to the leaves, consists of non-living tissue consisting of vessels and tracheids
• How is water uptaken?/transport occurs in plants roots how?

  Uptake of water + mineral ions = in roots

  taken up by ROOT HAIRS = large surface area for absorption

  IONS = absorbed into root by diffusion + active transport

  WATER = osmosis, along water potential. Soil has high water potential, root has less water potential

  WATER MOVEMENT= Gradient -> root hair cells -> cortex -> inner xylem vessels

  GRADIENT = maintained by continuous water movement up the xylem + dissolved ions in xylem sap
• what are mycorrhizae?

  • mutualistic/symbiotic with plant roots
  • fungus = absorbs mineral ions + water, pass on to root
  • receives nutrients from plant
  • hyphae can spread further than roots
• types of mycorrhizae?


  ECTROTROPHIC:

  • Form a sheath around the root and penetrate the air spaces between the cells in the cortex, but do not enter cells.
  • An extensive intercellular net is formed.
  • They are found mainly in forest trees

  ENDOTROPHIC:

  • occur in other plants
  • also form an intercellular network and extend into the soil
  • penetrate cells
• apoplast pathway?

  movement of water through cell walls via small intercellular spaces

  cell walls = fully permeable (except for endodermis)

  casparian strip = impermeable, prevents passage of water and ions via apoplast

  water is therefore forced to pass through symplast pathway. this allows control of movement into xylem
• symplast pathway ?

  movement of water through cytoplasm of adjacent cells

  water = through plasmodesmata

  plasmodesmata = stands of protoplasm linking cytoplasm of cells
• Structure of xylem structure?

  Tissue consists of: xylem vessels + tracheids

  Present in inner part of vascular bundle in stem

  Xylem = dead tissue (no cell contents)

  Hollow tubes allow minimal resistance of water flow

  Cell wall = strong because of lignin, allows rigidity, support, impermeable to water

  Cross walls = broken down to allow free flow

  Tracheids = end walls partiallay broken down

  Both Vessels + tracheids = holes allow water to move to other vessels
• transpiration?

  Evaporation of water from plants surface through stomata when they open
• environmental factors of transpiration?

  1. light

  When daylight, stomata = open for CO2

  Increased rate of transpiration as water evaporates, from mesophyll cells out of leaf

  
  

  2. temperature

  Increase temp = low humidity outside leaf, increased transpiration

  provides water with kinetic energy and allows evaporation

  
  

  3. humidity

  more humidity = less transpiration, water potential gradient decreases