Secondary growth is the increase in diameter of stems and roots due to activity of secondary meristem, called:

Explanation

Secondary growth is the increase in diameter of stems and roots due to activity of secondary meristem, called cambium.Cambium is a layer of meristematic tissue found in the stems and roots of vascular plants. It's responsible for secondary growth or lateral growth in plants, which results in the thickening of the plant body. Cambium cells are undifferentiated and actively dividing, which allows for the continued production of new cells. These new cells can mature into different types of tissues, contributing to both the plant's girth and the development of its protective outer layer.The growth produced by cambium is crucial for plants, particularly for woody perennials, as it enables them to become larger and stronger, providing support and allowing for the transport of water, nutrients, and organic compounds over long distances. This secondary growth allows trees to become taller and wider with each passing year.