Secondary Growth

Secondary growth refers to the increase in girth or diameter of a plant as a result of the activities of lateral meristems. It occurs in woody plants, such as trees and shrubs, and is responsible for the growth of the plant in width.

Lateral Meristems

Lateral meristems are meristematic tissues found in the cambium layer of the stem and root. They are responsible for the production of secondary tissues, which contribute to the increase in girth or diameter of the plant. There are two types of lateral meristems involved in secondary growth:

1. Vascular Cambium: The vascular cambium is a type of lateral meristem that is responsible for the production of secondary xylem (wood) and secondary phloem (inner bark). It is located between the primary xylem and primary phloem in the stem and root. The vascular cambium is responsible for the increase in girth of the plant.

2. Cork Cambium: The cork cambium is another type of lateral meristem that is responsible for the production of cork cells. It is located in the outer bark of the stem and root. The cork cambium produces cork cells on the outer side, which protect the plant from mechanical damage, water loss, and pathogens.

Process of Secondary Growth

Secondary growth occurs in two main steps:

1. Division and Differentiation of Lateral Meristems: The vascular cambium and cork cambium divide and differentiate to produce new cells. The vascular cambium produces secondary xylem cells towards the center of the stem and secondary phloem cells towards the outside. The cork cambium produces cork cells towards the outside.

2. Secondary Tissue Formation: The newly formed cells from the vascular cambium and cork cambium differentiate into secondary tissues. The secondary xylem cells form wood and contribute to the structural support of the plant. The secondary phloem cells transport sugars and other organic compounds throughout the plant. The cork cells form the protective outer bark.

Significance of Secondary Growth

Secondary growth plays a crucial role in the development and survival of woody plants. It allows the plant to increase its girth and provides structural support for upright growth. The secondary tissues formed through secondary growth, such as wood, provide strength and rigidity to the plant, allowing it to withstand environmental challenges like wind and gravity.

Conclusion

In conclusion, the increase in girth or diameter of a plant as a result of the activities of lateral meristems is known as secondary growth. The vascular cambium and cork cambium are the two types of lateral meristems involved in secondary growth, which produce secondary tissues like wood and bark. Secondary growth is essential for the structural support and survival of woody plants.