Plant tissues and organs

• What are the three main organs of a plant?

  stem- transporting substances through the plant

  Roots- absorb water and minerals

  Leaf- Carry out photosynthesis
• Tissue A group of cells with a similar structure and function
• Meristem -Found in the growing parts of stem and roots of a plant. It contains many stem cells- unspecialized cells with potential to develop into any plant cell
• Waxy cuticle- water proof layer
• Epidermal tissue- Covers the leaf. Thin so light can pass through
• Palisade mesophyll tissue- carries out photosynthesis contains many chloroplasts
• Spongy mesophyll tissue- allows gas exchange. Has air spaces to speed up diffusion
• Xylem- Transports water and minerals. Thick walls containing lignin. Water moves in one direction. Long hollow tube formed from dead cells
• Phloem vessels- transports sugar. Contains pores that allow sugar to move easily. Sugar can be transported in either direction depending on where it is needed. Made from living cells joined to form a tube.
• Stomata- takes in CO2 and release O2. Water vapour is lost through stomata.
• Guard cells change shape at night as there is no light for photosynthesis ( so no need to take in CO2 and they close to prevent water loss)
• Transpiration stream- Movement or flow of water from the roots to the leaves in xylem vessels
• Transpiration- Loss of water through stomata by evaporation
• Translocation- movement of sugar through the phloem.

  Sugar produced in leaves by photosynthesis and then transported to the meristem tissues or to storage organs by translocation