Land plants both tall and short need to grow vertically and form shoots that hold their leaves up to the sun and roots that push beneath the soil. This is all possible thanks to apical meristem.
Picture this: a seed lands in fertile soil just at the right depth. It receives water and sunlight and begins to sprout, or ‘germinate’. Germination produces a root, which begins to grow down into the soil to anchor the growing plant and to pull in necessary water and nutrients. Germination also produces a shoot that reaches up, holding the baby plant’s seed leaves up to the light to start photosynthesis.What happens to the plant from there is up to meristematic tissue, or stem cell-like tissue that creates undifferentiated cells that can become whatever the plant needs.
What Is Apical Meristem and What Does It Do?
Apical meristem is found at the apices, or tips of the plant, both the tip of the shoot and the root, and is a region of actively dividing cells.
The definition is easy to remember when you break it down. An apex (plural: apices) is the tip, the very end, of something. You can think of ‘meristem’ as any kind of plant tissue that is made of cells that don’t know what they want to be when they grow up, like happy, ‘merry’ children.
Apical meristem causes the plant to grow up and down to get longer. This kind of growth is called primary growth. When a plant grows ‘out’ or gets thicker, it’s called lateral or secondary growth. Both directions of primary growth are important, since it stretches the plant’s leaves to light and pushes its roots deep below the ground to seek out water and anchor the plant.
What Are the Products of Apical Meristem?
Division of apical meristem results in one of three kinds of primary tissue.
Primary tissue is partially differentiated. That is, the cells in these tissues have been set on the path to become a specific type of tissue, but the cells are still dividing to become further specialized. The three types of primary tissue are:
- Protoderm, which becomes the plant’s outer layer, the epidermis (you can remember this by remembering that ‘derm’ means ‘skin’).
- Procambium, which becomes a plant’s vascular tissue, either xylem to carry water or phloem to carry sugars.
- Ground meristem, which becomes any of the various types of ground tissue, the most common type of plant tissue. Ground tissue’s functions include storing starch, supporting the plant, and housing the chloroplasts that are vital for photosynthesis.
What if It’s Damaged or Removed?
As you might imagine, the cells that make up the apical meristem are delicate. As such, the plant has structures in place to protect them. A root cap covers dividing cells at the root tip. This cap also secretes a mucus-like material that helps the root push through the soil.The shoot tip’s meristem produces tissue called coleoptile, which protects the young shoot as it emerges from the seed and seeks daylight. Many plants also protect the shoot’s apical meristem by keeping the growing stem bent in a U-shape until the tip clears the soil.If apical meristem is damaged or destroyed, then the plant won’t grow in length.
This can be critical for the plant’s survival. If shoot apical meristem can’t push its seed leaves towards the light, then photosynthesis can be reduced or eliminated. If root apical meristem division is curbed, the plant will not be able to absorb water and nutrients properly.Note that plants can survive some loss of apical meristem. Horticulturalists (people who use science to produce specific results when growing and pruning plants) sometimes remove apical meristem at specific times during a growing season in order to produce more lateral (side-to-side) growth.
This method is also used to encourage fruit trees to produce more fruit. This technique is called overcoming apical dominance.
Apical meristem is a region of rapidly-dividing cells found at a plant’s root and shoot tips. Division of these cells always results in primary (vertical) growth, both at the root and shoot. This type of tissue is undifferentiated.
That is, it can become any of three types of tissue: protoderm, procambium, or ground meristem based on the plant’s needs.Since apical meristem is so crucial to plant growth, plants have adaptations designed to protect it. However, plants can survive some loss or damage to apical meristem. In fact, certain agricultural practices rely on removing apical meristem to yield more abundant crops.
Apical Meristem Overview
|Meristematic tissue||stem cell-like tissue that creates undifferentiated cells that can become whatever the plant needs|
|Apex/apices||the tip or the very end, of something|
|Primary growth||the apical meristem causes the plant to grow up and down to get longer|
|Protoderm||the plant’s outer layer, the epidermis|
|Procambium||a plant’s vascular tissue, either xylem to carry water or phloem to carry sugars|
|Ground meristem||any of the various types of ground tissue|
|Root cap||covers dividing cells at the root tip|
|Coleoptile||protects the young shoot as it emerges from the seed and seeks daylight|
Use the lesson to learn about or refresh your memory of the apical meristem, then:
- Give the definition of meristematic tissue
- State the purpose of the apical meristem
- List the three types of primary tissue
- Determine the implications of a damaged apical meristem