Formation of bark:
(i) Due to the presence of suberin in the walls of cells water cannot enter into them
(ii) As the cork cells do not get any Supply of water and food from the Inner conducting tissue, they gradually dry up and die and the dead cells are commonly known as bark. Thus, the dead cells form a hard layer around the stem. This hard coat which a formed outside the cork cambium or phelogen known as bark.
The bark is of two types; such as-
- Scally bark- Guava, Pine plant etc.
- Ringed bark- Mango, Lichi etc.
The bark is a water proof protective layer present on the trees to prevent loss of water through evaporation. Since it is majorly consists of dead cell, it forms a rigid covering that protects the interior of the plant from the entry of harmful micro-organisms, mechanical injury, high temperature, etc.
(i) It protects the plant from excessive heat and cold,
(ii) It reduces the rate of evaporation
(iii) It protects the inner tissue from dryness
(iv) It protects the Inner tissue from external hurt and the attack of fungi and bacteria
(v) It also gives a little mechanical support.