As we know that Intrafascicular/intrastelar cambium is present between xylem and phloem in dicot stem and roots. Pith rays, present between the edges of intrafascicular cambium, divide to form a new cambium strip between the two vascular bundle i.e. interfascicular cambium. Thus, inter and intra fascicular cambium together forms a complete cambium ring, called as vascular cambium, which forms secondary xylem on inner side and secondary phloem on outer side. Differential cambial activity during autumn and spring season result in narrow and wide secondary xylem rings respectively, which together forms the annual growth ring. Thus, annual growth ring is derived from vascular cambium, which is derived from inter and intrastelar cambium.

Growth rings, also known as annual rings, are concentric circles found in the trunk of trees. These rings are a result of the activity of the intrastelar cambium, which is responsible for the secondary growth of woody plants.

The intrastelar cambium is a type of meristem, which is a region of actively dividing cells. It is located within the stem or trunk of a tree, and it produces new cells that contribute to the growth in girth or diameter of the plant. The intrastelar cambium specifically produces secondary xylem and secondary phloem, which are the two types of tissues that make up the growth rings.

The formation of growth rings occurs during the growing season of a tree, which is typically in the spring and summer. During this time, the intrastelar cambium produces new cells that differentiate into xylem towards the inside and phloem towards the outside. As a result, the tree trunk increases in diameter.

Each year, the growth rings are formed by the intrastelar cambium as it produces a new layer of secondary xylem and secondary phloem. The cells that are produced early in the growing season are larger in size and have thin cell walls, resulting in a lighter-colored wood known as earlywood. As the growing season progresses, the cells become smaller and have thicker cell walls, creating a darker-colored wood known as latewood. The transition from earlywood to latewood forms a distinct boundary known as a growth ring.

By counting the number of growth rings, scientists can determine the age of a tree. Each growth ring represents one year of growth. The width of the growth rings can also provide information about the environmental conditions during that particular year, with wider rings indicating favorable conditions and narrower rings indicating less favorable conditions.

In summary, growth rings are formed due to the activity of the intrastelar cambium, which produces new layers of secondary xylem and secondary phloem during the growing season. These rings can be used to determine the age of a tree and provide information about past environmental conditions.

Intrafasicular cambium undergo diffrention and form interfasicular cambium by medullary adjoining rays will connect.