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
• epidermal tissue - this covers the whole plant. it is covered with a waxy cuticle, which helps to reduce water loss by evaporation
• palisade mesophyll tissue - this is the part of the leaf where most photosynthesis happens. it has lots of chloroplasts so it means that they are at the top of the leaf where they can get the most light
• the upper epidermis is transparent so that the light can pass through it to the palisade layer
• spongy mesophyll tissue - this is also in the leaf, and contains big air spaces to allow gases to diffuse in and out of cells
• the xylem and the pholem transport things like water, mineral ions and food around the plant. they form a network of vascular bundles which help deliver water and other nutrients to the entire leaf and take away the glucose produced by photosynthesis. they also help support the structure
• meristem tissue - this is found at the growing tips of shoots and roots and is able to differentiate into lots of different types of plant cell, allowing the plant to grow
• the tissues of leaves are also adapted for efficient gas exchange. the lower epidermis is full of little holes called stomata which let C02 diffuse directly into the leaf. the opening and closing of the stomata is controlled by guard cells in response to the environmental conditions. the air spaces in the spongy mesophyll tissue increase the rate of diffusion of gases