Plant Tissues

Different parts of plants are made up of different types of plant tissue. The structure of each type of plant tissue is related to its function.

Plant tissues form plant organs, which include roots, stems and leaves.

The leaves are the organs for photosynthesis and they have many adaptations to help them carry out photosynthesis effectively. This involves carrying out the following processes:

  • Exchanging carbon dioxide and oxygen
  • Absorbing light energy efficiently
  • Ensuring water is transported to the leaf and glucose is transported to other parts of the plant

The table below shows the structure and function of different structures of a leaf.

StructureFunction
Waxy cuticleProtective, waterproof layer on top of the leaf that reduces water loss by evaporation
Upper epidermisA thin and transparent layer of cells that allows light to pass straight through (it has no chloroplasts)
Palisade mesophyllTightly packed palisade cells, which contain a lot of chloroplasts – Photosynthesis mostly takes place in the palisade mesophyll
Spongy mesophyllContains spaces that increase the surface area to volume ratio for the diffusion of gases
Vascular bundleContains the xylem and phloem tubes, which transport substances to and from the leaf
XylemNarrow, hollow tubes that transport water and minerals from the roots, up the stem and into the leaves
PhloemHollow tubes that transport amino acids and sugars around the plant
Lower epidermisContains guard cells and tiny holes called stomata, which allow gases to diffuse in and out of the leaf
Guard cellOpens and closes the stomata by absorbing and losing water, which allows carbon dioxide to diffuse in and oxygen to diffuse out
StomataMicroscopic openings on the surfaces of leaves and stems that allow for gas exchange

Stomata close to minimise water loss and open to increase evaporation and transpiration. When they are open, gas exchange can occur

Leaf Adaptations for Efficient Photosynthesis

The structure of leaves has adapted over time to be efficient at photosynthesis. The table below shows the main adaptations of leaves and their functions:

AdaptationFunction
Thin shapeThis means there is a short distance for carbon dioxide to diffuse in and oxygen to diffuse out. If there is a shorter diffusion distance, then diffusion happens at a faster rate.
Large surface areaThe leaf can absorb a lot of light for photosynthesis
Waxy cuticleAllows light in while preventing water loss
Thin and transparent epidermisAllows light to reach the palisade mesophyll cells
Network of veinsSupports the structure of the leaf and transports substances to and from the cells
ChlorophyllAbsorbs light energy for photosynthesis and gives the leaf its green colour

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