Plant Cell Organisation

• 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 - for example, transporting substances around the plant. Plant organs are made of tissues. Examples of plant tissues are: Epidermal tissue, Palisade mesophyll tissue, Spongy mesophyll tissue, Xylem, Phloem and Meristem tissue.
• Epidermal tissue is a plant tissue that covers the whole plant.
• Palisade mesophyll tissue in a plant is the part of the leaf where most photosynthesis happens.
• Spongy mesophyll tissue in a plant is in the leaf and it contains big air spaces to allow gases to diffuses in and out of cells.
• Xylem and phloem in a plant transport things like water, mineral ions and food around the plant (through the roots, stems and leaves).
• Meristem tissue in a plant is found at the growing tips of shoots and roots and is able to differentiate (change) into lots of different types of plant cell, allowing the plant to grow.
• Leaves contain epidermal, mesophyll, xylem and phloem tissues.
• In a plant, the epidermal tissues are covered with a waxy cuticle, which helps to reduce water loss by evaporation.
• In a plant, the upper epidermis is transparent so that light can pass through it to the palisade layer.
• In a plant, the palisade layer has lots of chloroplasts (where photosynthesis takes place). This means that they're near the top of the leaf where they can get the most light.
• In a plant, 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 support the structure.
• In a plant, the tissues of leaves are also adapted for efficient gas exchange. E.g. the lower epidermis is full of little holes called stomata, which let CO2 diffuse directly into the leaf. The opening and closing of 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.