Plant Cell Organisation

• Plants are made of organs like stems, roots and leaves
• Examples of plant tissues:

  • epidermal tissue - covers the whole plant
  • palisade mesophyll tissue - part of the leaf where photosynthesis happens
  • spongy mesophyll tissue - part of the leaf that contains big air spaces to allow gases to diffuse in and out of cells
  • xylem and phloem - transport things like water, mineral ions and food around the plant through the roots, stems and leaves
  • meristem tissue - the growing tips of roots and shoots and is able to differentiate into lots of different types of plant cell, allowing it to grow
• Leaves contain mesophyll, epidermal, xylem and phloem tissues
• The epidermal tissues are covered with 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
• The palisade layer has lots of chloroplasts, which means that they're near the top of the leaf where they can get the most light
• The xylem and phloem form a network of vascular bundles, which deliver water and other nutrients to the entire leaf and take away the glucose produced by photosynthesis. They also help support the structure
• The tissues of the leaves are adapted for efficient gas exchange:

  • the lower epidermis is full of little holes called stomata which let carbon dioxide diffuse directly into the leaf
  • the opening and closing of the stomata is controlled by guard cells in response to environmental conditions
  • the air spaces in the spongy mesophyll tissue increase the rate of diffusion of gases