Lateral meristems
The third meristem is the one that makes a stem thick rather than long, and it is the one you have already met under another name.
Lateral meristem
Found at the sides of the stem and the root, lying parallel to the long axis of the plant. Because of the activity of lateral meristematic tissue, the stem increases in girth.
The cambium
The cambium tissue found in dicotyledonous plants is a lateral meristematic tissue. In a stem it forms a thin cylinder running the whole length of the stem, just inside the bark — which is why a cross-section shows it as a ring.
This is the layer you matched when grafting
In grade 10, grafting worked only if the cambium of the scion was lined up with the cambium of the stock. Now the reason is plain: the cambium is the dividing layer, so it is the only tissue that can grow new cells across the join and knit the two plants into one. Match anything else and nothing grows together.
The three meristems together
| Meristem | Where it sits | What its activity produces |
|---|---|---|
| Apical | Shoot and root apex, axillary buds | The plant increases in height |
| Intercalary | At the bases of the internodes; abundant in grasses | The internodes increase in length |
| Lateral | At the sides of stem and root, parallel to the long axis | The stem increases in girth |
Three meristems, three kinds of growth
Apical makes a plant taller, intercalary makes its internodes longer, and lateral makes it thicker. The cambium of a dicot is a lateral meristem.