Meristems

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Plant growth is largely restricted to specialised regions of active cell division called meristems. Special cells called initial cells, which complete the cell life cycle (i.e., they divide), are found in meristems.

Apical meristems – occur near the tips of roots and shoots and produce primary tissues. These meristems account for primary growth, which is the elongation of roots and shoots. Enables plant to extend in to new environments that may provide light, water, and nutrients. The shoot apical meristem produces young leaves and axillary buds, which usually overarch the meristem. The root apical meristem is covered by a thimble shaped root cap that protects the meristem as the root grows through the soil.

Axillary buds – are left behind during primary growth as a stem elongates. They occur in the axil of a leaf (the angle between leaf and stem) and typically undergo a dormant period. Axillary buds contain inactive cells that can form a branch, a leaf, or a flower when the bud breaks dormancy and resumes growth and development.

Lateral meristems – are cylindrical meristems that form in mature regions of the roots and shoots of many plants, particularly those that produce woody stems. Lateral meristems produce secondary growth, which increases girth or width of the plant.

Intercalary meristems - occur between mature tissue. These meristems are most common in grasses, where they occur throughout slender leaves.