Root and Shoot Growth: Length vs. Width

Root and shoot growth in vascular plants happens in two main ways: primary growth and secondary growth. Primary growth makes roots and shoots longer. Secondary growth makes them thicker. Many woody plants show both kinds of growth, and the two can happen at the same time.

Primary growth happens i...

As a plant grows, the shoots and roots lengthen through primary growth and, in woody plants, thicken through secondary growth.

In stems, primary growth begins when undifferentiated cells in the shoot apical meristem divide. Some progeny cells differentiate into primary meristems—the protoderm, ground meristem, and procambium.

Ult...