2.4.1 Plant Tissues

Plants are made up of many different tissues to allow it to carry out its function.

Tissue	Features	Function
Epidermal tissue covers the whole plant.	Covered with a waxy cuticle.	Helps to reduce water loss by evaporation, as the waxy cuticle prevents water from moving out.
Palisade mesophyll tissue found underneath the epidermal tissue.	Has lots of chloroplasts (photosynthesis takes place within these structures).	Having many chloroplasts means photosynthesis can happen rapidly. They are positioned at the top of the leaf so they receive lots of light.
Spongy mesophyll tissue found underneath the palisade mesophyll.	Has lots of air spaces.	This allows gases to diffuse in and out of cells.
Xylem is found in the roots, stems and leaves.	Made up of dead cells joined together, creating a continuous tube.	Allows the movement of water and mineral ions from the roots to the stem and leaves, where it evaporates and leaves the plant. This called the transpiration stream.
****	Strengthened with a substance called lignin, but this has some holes in it along the tube called bordered pits.	Lignin makes it strong and waterproof, so water will not leave except at bordered pits, allowing minerals to go to specific places in the plant.
Phloem is found in the roots, stems and leaves.	Elongated cells with holes in the cell walls (the end walls are now called sieve plates ). Many organelles from the cells are removed so cell sap can move through.	Food substances can be moved in both directions, from the leaves where they are made for use, or from storage (underground) to parts of the plant that need it. This process is called translocation.
Meristematic tissue is found at the tips of shoots and roots	It is able to differentiate into different types of plant cell.	This allows the plant to grow.

infoNote

The leaf is a plant organ, and has the following tissues: epidermis, palisade, spongy mesophyll, xylem and phloem, and guard cells (these surround the stomata and control the opening and closing of them, depending on the water availability).

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2.4.1 Plant Tissues

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