B2 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
• The upper epidermis is transparent so that light can pass through it. This means that as much light as possible can reach the palisade mesophyll cells below, and be used in photosynthesis.
• Meristem tissue is made up of plant stems cells. It's found in the growing parts of the plant such as the tips of shoots and roots.