분열조직과 식물 성장

Unlike most animals, plants can grow throughout their lives. Plant growth is facilitated by meristems, tissues containing undifferentiated cells that can perpetually divide—akin to animal stem cells.  

All vascular plants undergo primary growth, which lengthens roots and shoots. 

Primary growth begins in apical meristems, located at the tips of stems and roots. Here, undifferentiated cells divide. Some daughter cells remain in the meristem and go on to divide again. Others partially differentiate into primary meristems.

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

The protoderm becomes dermal tissue, 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 rarely leaves.

Two lateral meristems contribute to secondary growth: the cork cambium and the vascular cambium.

The cork cambium produces cork to the outside and phelloderm to the inside, forming the periderm.