plant tissues, organs & systems

• what does the epidermal do?

  protects the surface of the leaf
• what is the key adaptation of the upper epidermis?

  • its transparent-this allows light to pass through to the photosynthesis cells below
  • it is covered with a thin layer of oily material called waxy cuticle-the waxy cuticle reduces the evaporation of water from the surface of the leaf this helps to prevent the leaf from drying out
• what happens in the lower epidermis?

  stomata regulate gas exchange they also help to control the amount of water vapour that can pass out of the leaf
• where do we find the palisade mesophyll?

  at the top of the leaf
• what do palisade mesophyll contain?

  palisade cells which are packed full of chloroplasts
• what do chloroplasts contain?

  chlorophyll which absorbs the light energy needed for photosynthesis
• what is the key feature of spongy mesophyll?

  it is full of air spaces - the air spaces allow co2 to diffuse from the stomata through the spongy mesophyll to the palisade cells
• oxygen also diffuses from the palisade cells through the spongy mesophyll to the stomata
• what does the xylem transport?

  water from the roots to the stem and leaves

  mineral ions
• what does the phloem transport?

  dissolved sugars produced by photosynthesis from the leaves to the rest of the plant
• sugars from the phloem can be used immediately

  and can be stored
• what is the movement of sugars and other molecules through phloem tissue called?

  translocation
• where do we find meristem tissue?

  at growing tips (shoots and roots)
• meristem tissue contain stems cells which can differentiate into different types of plant tissue