Meristems and Plant Growth

Plants can grow throughout their lives, unlike most animals, which stop growing after reaching a certain age.

Plant growth begins in meristems, tissues that contain undifferentiated cells. These cells can either remain meristematic or differentiate into specialized tissues.

Vascular plants grow longer through primary growth, which lengthens roots and shoots.

Primary growth begins in the apical meristems at the tips of roots and shoots. Cells in these regions divide by mitosis. Some daughter cells remain meristematic, while others begin to differentiate into the primary meristems.

The primary meristems—the protoderm, ground meristem, and procambium—differentiate into distinct primary tissues.

The protoderm becomes dermal tissue, which forms the protective outer layers. The ground meristem develops into ground tissue, which makes up most of the body of a young plant. The procambium forms vascular tissue, including xylem and phloem.

In addition to primary growth, woody plants also undergo secondary growth. Secondary growth widens roots and stems, but it rarely affects leaves. Two lateral meristems contribute to secondary growth: the cork cambium and the vascular cambium.

The cork cambium pro