plant tissues

• Epidermal cells


  Very thin cells that form the upper and lower epidermis of a leaf
• Upper epidermis


  • Transparent to allow light to pass through
  • Covered in a waxy cuticle to reduce water evaporation
• Lower epidermis


  • Contains tiny pores called stomata
  • Stomata allow carbon dioxide to enter and oxygen to leave
• Guard cells


  Found on either side of stomata and help control water vapor passing out of the leaf
• Palisade mesophyll


  • Packed full of chloroplasts to absorb light energy for photosynthesis
• Spongy mesophyll


  • Full of air spaces to allow carbon dioxide and oxygen to diffuse
• Xylem


  Transports water and dissolved mineral ions from roots to stem and leaves
• Phloem


  Transports dissolved sugars produced by photosynthesis from leaves to rest of plant
• Translocation


  Movement of sugars through phloem tissue
• Meristem tissue


  Contains stem cells that can differentiate into different plant tissues
• Meristem tissue is found in growing tips of shoots and roots
• compare the structure of xylem and phloem

  xylem is is made of dead cells while phloem is made of living

  phloem cells ahve pores on their end walls while xylem does not

  xylem is hollow and doesnt contain cytoplasm while phloem contains cytoplasym

  both made of cells

  xylem transports mineral ions and water while phloem transports dissolved sugars
• what is meant by diffusion

  diffusion is the movement of water form an area of high concerntrtion to an area of low concertration
• Explain one way the removal of dissolved sugars from the stem of the plant causes stunted growth.

  less sugars for respiration so less energy released

  less amino acids made so less protein produced or less protein synthesis
• When light intensity is high potassium ions are moved into the guard cells. Describe how the movement of potassium ions into the guard cells causes the stoma to open.

  pottasium ions movr into gard cells by osmosis therefore making it swell unevenly and causing it open
• Root hair cells take up water from the soil. Explain one way in which the root hair cell is adapted to this function

  large surface area for faster osmosis

  thin walls for short diffusion distance
• Explain why root hair cells contain mitochondria

  aerobic respiration occurs in mitochondria , thireleases enegy the energy is then used for active transport
• Describe how water moves from roots to the leaves

  by transpiration stream / pull 1 in xylem
• Describe how ions, water and sugar are obtained and transported

  water taken up by osmosis from an area of low to high concentration travels in the xylem, to the leaves or from the roots

  transpiration stream movement replaces water as it evaporates from leaves in the xylem