The Concept of Cork Cambium and Growth

Secondary growth in plants is defined as the thickening of the stem and root due to the activity of the lateral meristems, which are absent in herbaceous plants. In layman’s words, it’s the plant’s outward growth. 

Secondary growth is critical in woody plants because they grow considerably taller than other plants and require more root and stem support. 

The vascular cambium and the cork cambium makeup lateral meristems, which play a key role in plant secondary growth.

 The plant’s secondary growth is directly influenced by the growth of these tissues. The genesis and structure of secondary vascular tissues will be discussed in this topic.

Secondary growth in stem

For woody plants, the vascular cambium and cork cambium play a key role in developing stem thickness. 

The production of secondary xylem and secondary phloem cells results from the division of vascular cambium cells into xylem and phloem cells, and the increase in thickness is related to the formation of secondary xylem and secondary phloem cells. 

The plant’s bark is made up of cork cambium tissue. It also contains the suberin, a water-repelling chemical that helps the bark endure various environmental variables.

The periderm, a layer of cells in the vascular cambium system that aids in the flow of gasses between the atmosphere and the inner cells, also plays a function in stem growth. 

Secondary growth in root

Secondary tissues and branch roots are produced by roots at the expense of primary tissues. As secondary growth progresses, cells in the main tissue are eliminated. 

On their way to the soil, new lateral roots grow within the root system and push outward from the pericycle, killing cortical and epidermal tissues in the process.

 In the root system, secondary growth begins in the maturation zone shortly after the cells stop elongating there. 

In this zone, the vascular cambium distinguishes between primary xylem and primary phloem cells, and the pericycle cells divide at the same time as the procambium initiates. This results in the creation of a cambium cylinder that encircles the major xylem.

The vascular cambium system begins developing xylem cells inward and phloem cells toward the root’s exterior nearly immediately. This causes the primary phloem to flatten against the more resistant endodermis.

 The addition of new areas of cell division in the stele is made possible by the simultaneous differentiation of cork cambium in the pericycle. 

The cambia isolates the outer tissues from their source of supplies in the interior of the root by combining vascular tissue and periderm formation, which splits the remaining cells of the cortex and epidermis and lays down lignified and suberised new cell walls.

Secondary growth eliminates all except the central core of primary xylem cells and a few primary xylem fibers pressed against the periderm by the end of the first year. 

Periderm, pericycle, primary and secondary phloem, vascular cambium, secondary and primary xylem are the zones at this period, from outside to within.

Abnormal Secondary Growth

Secondary development that does not follow the pattern of a single vascular cambium produces xylem on the inside and phloem on the outside is common in dicots like Bougainvillea, Dracaena, and others, where a series of cambia arise outside the oldest phloem.

 In arborescent monocot stems, abnormal secondary growth is seen when a secondary cambium grows in the hypodermal area, forming conjunctive tissue and patches of meristematic cells. 

Secondary vascular bundles develop from these patches of cells. The bundles can be seen in both the cortex and the pith.

Conclusion

In many vascular plants, a cork cambium is a form of meristematic tissue. It is specifically a lateral meristem, which is a meristem that is responsible for plant lateral growth. 

Secondary growth is critical in woody plants because they grow considerably taller than other plants and require more root and stem support.

In woody trees and certain herbaceous plants, the cork cambium is the meristem that is responsible for the development of cork or phellem.

An epidermal layer (epidermis) serves as an outer protective covering for a new plant at first. The epidermis would be replaced by a periderm, a harder outermost protective layer of the bark.