1. MULTICELLULAR ORGANISMS
Section 2b – Plant Meristems

2. Re-Cap Can you name the following cells:
Can you describe their functions

3. Learning Outcomes Today we will learn:
- the sites of growth in a plant
- the importance of meristems
- the way that cells specialise in plants

4. Boardworks GCSE Additional Science: Biology Growth and Development
Plant vs. animal growth
How is the growth of plants different to the growth of animals?
Many plants can continue growing throughout their lifetime.
Most plant growth occurs by cell elongation, not cell division.
Growth in plants only occurs in certain tissues.
Many plant cells retain the ability to differentiate into any cell type. This is why cuttings can be used to create new plants.

5. Boardworks GCSE Additional Science: Biology Growth and Development
How do plants grow?
Cell division only takes place in regions of the plant called meristems. These tissues are found in the tips of the roots and shoots – they are therefore apical meristems.
zone of cell division
meristem
zone of cell elongation
Plants only get taller when cells in meristems elongate following cell division.
zone of cell differentiation
After this, cells differentiate into their final form.
Teacher notes
Meristems in the tips of roots and shoots are called apical meristems. Growth here is called primary growth and mainly results in an increase in height.
Woody plants, such as trees are shrubs, also show secondary growth. This takes place in lateral meristems and results in an increase in girth. Many non-woody plants only grow by primary growth and do not show an increase in girth. These plants generally have short life spans as cells produced by primary growth generally die after 3-5 years.

6. Plant Cell differentiation
Initially cells will elongate
Then they will develop a vacuole
- vacuolation
Then the cells will specialise
- differentiation
Xylem
- will lose the vacuole, and become hollow
- will develop lignin

7. Boardworks GCSE Additional Science: Biology Growth and Development
Animals, plants or both?
Teacher notes
This ‘animals, plants or both’ activity could be used as a plenary or revision exercise on mechanisms of growth. Coloured cards (red = animals, green = plants, blue = both) could be used to make this a whole-class exercise.

8. Lateral Meristems Some plants grow every year - perennial
Their stems need to thicken to support the extra growth
This thickening is controlled by lateral meristems
These cause the stem to get wider every year
This is seen in rings within the stem

9. Cambium
A young plant will start off with a single band of xylem and phloem
Each year a new band (or ring) of xylem will develop
The phloem will also widen
This allows the xylem and phloem to reach the top of the plant
In between the xylem and phloem is a region called cambium
Cambium is a lateral meristem
– it produces the new xylem and phloem cells

10. Re-Cap questions 1) What is a meristem?
2) Identify 2 regions of a plant which possess an apical meristem?
3) State 2 differences between a xylem vessel and a meristematic cell
4) Give ONE way in which growth in an animal differs from growth in a plant