What distinguishes primary growth from secondary growth in plants?

Primary growth in plants refers to the process of elongation, leading to an increase in height, which occurs primarily at the tips of roots and shoots. This is facilitated by the activity of apical meristems—specialized areas of undifferentiated cells. As the apical meristems divide and expand, they push the plant body upwards and downwards into the soil, respectively.

On the other hand, secondary growth pertains to the increase in thickness or girth of the plant, primarily driven by lateral meristems such as the vascular cambium and cork cambium. This growth is responsible for the formation of woody tissues in dicots and gymnosperms, allowing the plant to support greater weight and increase its structural integrity.

Understanding the distinction between these growth types is vital for grasping how plants develop over time. In this case, the correct choice highlights that primary growth contributes to height, while secondary growth results in increased thickness, which are fundamentally different processes in plant development.