3.2.3 Intercalary meristem — How do plants grow after being cut?

How do plants grow after being cut?

Node (where leaves/branches arise)

Internode (stem between nodes)

Intercalary meristem (near the node)

Grass regrows after mowing

• If the tip of a young stem is cut , the apical meristem is removed . The stem then stops growing in length .
• But new branches arise from the nodes of the stem (Fig. 3.5). So there must be dividing cells somewhere else as well.
• When a hedge around a garden is cut, more branches appear after some time, giving the hedge a bushy appearance . Grass also appears again after being mowed or grazed by animals.
• These dividing cells lie near the nodes , in between — this tissue is the intercalary meristem .
• This happens because of the presence of the intercalary meristem at the nodes of the stem .

Where is the intercalary meristem found?

Intercalary

Meristem

• It is found at the base of the internodes , just above the nodes .
• A node is the point on the stem where branches or leaves arise.
• An internode is the part of the stem between two nodes.
• It is found mainly in grasses and similar plants, which regenerate after cutting.

Comparison of all three types of meristematic tissue

Meristem	Where found	What it does
Apical	Root tips and shoot tips	Increases length
Lateral	A ring along the circumference of the stem	Increases girth
Intercalary	Base of the internodes, near the nodes	Helps regrowth after cutting

Apical — root & shoot tips — length

Intercalary — near nodes — regrowth

Lateral — ring in stem — girth

Apical — root & shoot tips — length

What do meristematic cells look like?

Meristematic Cell — What We See

Feature	Description
Size and wall	Small cells with thin cell walls
Nucleus	Large and prominent
Cytoplasm	Dense, with many organelles
Vacuoles	Generally absent
Packing	Tightly packed, with little or no intercellular space

Thin cell wall

Large prominent nucleus

Dense cytoplasm

No large vacuole

Cells tightly packed

• They are small , with thin cell walls .
• They have a large and prominent nucleus , and dense cytoplasm with many organelles .
• Vacuoles are generally absent .
• The cells are tightly packed , with little or no intercellular space .
• These characteristics allow them continuous and rapid cell division .

Differentiation Process

What is differentiation?

Differentiation

Meristematic Tissue

cells that keep dividing

→

Permanent

Tissue

cells with a

fixed job

↓

Differentiation is the process by which meristematic tissue becomes specialised to perform specific functions (support, transport, storage) and so becomes permanent tissue.

Dividing meristematic cell

Stops dividing

becomes specialised

stops dividing

Changes shape and job (specialises)

Permanent tissue (e.g. sclerenchyma)

Permanent tissue

• The cells that lose the ability to divide undergo changes in structure and function , and become permanent tissues .
• These cells become specialised to perform specific functions , such as support, transport or storage .
• This process of taking up a fixed job is called differentiation .
• Through differentiation, meristematic tissue becomes permanent tissue .

In short: Meristematic tissue becomes permanent by the process of differentiation.

• Plants have three meristems: apical, lateral and intercalary.
• Meristematic cells are small, thin-walled and lack vacuoles.
• By differentiation, meristematic tissue becomes permanent tissue.

• Intercalary meristem — meristem near the nodes that helps regrowth after cutting.
• Node — the point on a stem where branches or leaves arise.
• Internode — the part of the stem between two nodes.
• Differentiation — the process by which meristematic tissue becomes specialised to perform specific functions, such as support, transport or storage, and so becomes permanent tissue.