Cork Cambium

Cork cambium, also known as phellogen, is a type of lateral meristem found in woody plants. It is responsible for the formation of cork, which is the outermost layer of the bark. Cork cambium is a secondary meristem, meaning it is responsible for secondary growth in plants.

Formation of Cork Cambium

1. Cork cambium originates from the outer layers of the cortex or the phloem in the stem, root, or branches of a plant.
2. It is formed as a result of the activity of the primary meristem called the phellogen.
3. The phellogen is a layer of actively dividing cells that are located just beneath the epidermis.
4. These cells divide periclinally, meaning they divide parallel to the surface of the plant.
5. The cells produced by the cork cambium towards the outside differentiate into cork cells, while the cells towards the inner side differentiate into phelloderm cells.

Function of Cork Cambium

1. The cork cambium produces cork cells, which are dead at maturity and form the protective outer layer of the bark.
2. Cork cells are characterized by their thick cell walls containing a substance called suberin, which makes them impermeable to water and gases.
3. The formation of cork protects the plant from mechanical damage, pathogens, and extreme temperatures.
4. As the cork cells are dead, they also provide insulation to the plant.
5. The phelloderm cells produced by the cork cambium towards the inner side of the plant function as a replacement for the destroyed cortex.

Secondary Growth

Secondary growth is the increase in girth (diameter) of woody plants. It occurs due to the activity of lateral meristems, primarily the vascular cambium and the cork cambium.

1. Vascular Cambium:
- The vascular cambium is a type of lateral meristem that is responsible for the production of secondary xylem (wood) towards the inside and secondary phloem towards the outside.
- The secondary xylem provides structural support to the plant and transports water and minerals from the roots to the leaves.
- The secondary phloem transports the products of photosynthesis from the leaves to other parts of the plant.

2. Cork Cambium:
- The cork cambium is another type of lateral meristem that is responsible for the production of cork towards the outside and phelloderm towards the inside.
- The cork cambium replaces the epidermis with a protective layer of cork cells, which prevents water loss and protects the inner tissues.
- The phelloderm cells produced by the cork cambium function as a replacement for the destroyed cortex.

Primary Growth vs Secondary Growth

Primary growth refers to the increase in length of the plant. It occurs due to the activity of apical meristems located at the tips of roots and shoots. Primary growth is responsible for the formation of primary tissues, such as the primary xylem, phloem, and epidermis.

Secondary growth, on the other hand, refers to the increase in girth of the plant. It occurs due to the activity of lateral meristems, primarily the vascular cambium and the cork cambium. Secondary growth is responsible for the production of secondary tissues, such as secondary