2.5 transport systems in plants

• plant organs


  roots, stems, and leaves

  
• transport system


  osmosis moves the water from the soil to the root hair cell to the root cortex cell to the xylem vessel

  
• stage 1/4 transport system

  water enters roots via osmosis

  
• stage 2/4 transport system

  water travels through root tissue by osmosis until it reaches xylem

  
• stage 3/4 transport system


  xylem transports water up stem to leaves (unidirectional process) aided by build-up of root pressure + evaporation in leaves

  
• stage 4/4 transport system


  water moves through leaf cells by osmosis + exits by evaporation

  
• root hairs


  absorbs water + minerals from soil + increase surface area

  
• xylem


  water + mineral transport tissue of plant

  
• what is xylem made of?


  dead empty cells, hollowed with no cytoplasm, lignified to make it impermeable + gives it a strong structure, able to withstand high pressure built up from water + minerals moving through to different parts of plant tissue

  
• lignin


  polymer which makes a strong + waterproof structure

  
• pit


  thin area of cell wall in xylem

  
• how do minerals enter?

  by active transport + travel via diffusion through root + xylem, then diffuse into the leaf

  
• transpiration


  water moves through the leaf + exits via evaporation from stomata

  
• potometer


  measures rate of transpiration

  
• how does a potometer work?

  as water evaporates from the leafy shoot, water is drawn up from the cut stem through the capillary tube, so the air bubble moves down, faster transpiration = faster bubble moves

  
• what happens to the rate of transpiration when wind speed is increased?

  it increases because rate of evaporation from stomata increases

  
• what happens to the rate of transpiration when humidity is increased?

  it decreases because there is a lower diffusion gradient of water vapour from air spaces in leaf to air outside leaf

  
• what happens to the rate of transpiration when temperature is increased?

  it increases because rate of evaporation from stomata increases

  
• what happens to the rate of transpiration when leaf surface area is increased?

  it increases because more area = more stomata = more transpiration

  
• waxy cuticle


  reduces rate of water loss from leaf surface

  
• location of upper epidermis cells

  located here

  
• chloroplasts


  site of photosynthesis

  
• vascular bundle / vein


  xylem + phloem

  
• phloem


  living plant transport tissue in stem, transports sugars made in photosynthesis

  
• what is phloem made of?

  made of sieve tube, endwall/sieve plate, companion cell

  
• translocation


  sugars can travel up and down the phloem and to leaves and roots
• location of spongy mesophyll cells

  
• guard cell


  control the opening and closing of stoma

  
• air spaces


  water moves from xylem to air spaces via osmosis

  
• stoma(ta)


  pores on the underside of the leaf epidermis