plant cell organisation

• plant cells are organised into tissues and organs
• plants are made of organs like stems, roots and leaves
• plant organs work together to make organ systems - these can perform the various tasks that a plant needs to carry out to survive and grow
• plant organs are made of tissues, examples of plant tissues are:

  • epidermal tissue
  • palisade mesophyll tissue
  • spongy mesophyll tissue
  • xylem and phloem
  • meristem tissue
• epidermal tissue

  • this is a protective layer that covers the whole plant
  • the epidermal tissue is covered in a waxy cuticle, which helps to reduce water loss by evaporation
  • the upper epidermis is transparent so that light can pass through it to the palisade layer
• palisade mesophyll tissue

  • this is the part of the leaf where most photosynthesis happens
  • the palisade layer has lots of chloroplasts - this means that they are near the top of the leaf where they can get the most light
• xylem and phloem

  • they transport substances like water, mineral ions and food around the plant
• meristem tissue

  • this is found at the growing tips of shoots and is able to differentiate into lots of different types of plant cell, allowing the plant to grow
• phloem tubes transport food
• phloem tubes are made of columns of elongated living cells with small pores in the end walls to allow cell sap to flow through
• phloem transports food substances made in the leaves to the rest of the plant for immediate use or for storage
• phloem transports substances in both directions - this process is called translocation
• xylem tubes take water up
• xylem tubes are made of dead cells joined end to end with no end walls between them and a hole down the middle
• xylem tubes are strengthened with a material called lignin
• xylem tubes carry water and mineral ions from the roots to the stem and leaves
• the movement of water from the roots, through the xylem and out of the leaves is called the transpiration stream