plant structure

• xylem v phloem

  xylem

  *made up of dead cells + strengthened by lignin

  have no end walls

  have no subcellular structures

  phloem

  *made up living cells

  have sieve plates between cells (allows substances through)

  have subcellular structures e.g cytoplasm
• leaf structure


  waxy cuticle

  *water proof to stop water loss from top of leaf

  upper epidermis

  *transparent to let light through

  palisade mesophyll

  *has many chloroplasts

  spongy mesophyll

  gaps for gas exchange (large surface area)

  vascular bundle

  *contain xylem and phloem

  lower epidermis

  stomata

  *holes in lower epidermis (allow gasses in/out + water)

  gaurd cells

  *help regulate transpiration rate by opening and closing the stomata
• plant structure


  flower

  *reproductive hormones

  meristem

  *stem cell production

  leaf

  *photosynthesis & gas exchange, water evaporating out

  xylem

  *continous tubes thst carry water & dissolved mineral ions upwards

  phloem

  *tubes of cells that carry sugars(sucrose) + other nutrients

  roots

  -water enters through osmosis, mineral ions by active transport
• Transpiration (xylem)


  Evaporation of water from the leaf's surface due to the opening of the stomata
• Factors affecting rate of transpiration

  • Light intensity
  • Temperature
  • Air flow
  • Humidity
• Light intensity


  • brighter light = more photosynthesis
  • Stomata opens to let in CO2, also lets out water
• Warm temperatures


  • Provide water molecules with more kinetic energy so they are more likely to evaporate & diffuse out of stomata
• Air flow


  • Strong winds quickly blow away water molecules leaving leaf, concentration gradient between inside & outside leaf is high
• Humidity


  • High humidity decreases concentration gradient, less water diffuses out stomata
• translocation (phloem)


  -phloem tubes conneted end to end

  *sieve plates allow movement of cell sap (mixture of water & sugar)

  -transports nutrients in different directions (to be used/stored)

  *companion cells with many mitochondria to provide energy