Why are xylem and phloem called complex tissues? How are they different from one other?
Sol.
Tissues are of different types- simple and complex. A complex tissue consists of more than one type of cells having a common origin which coordinate to perform a common function. Xylem and phloem are called complex tissues because they are made up of different types of cells.
Xylem consists of four different types of elements-
Xylem |
Phloem |
It helps in the conduction of water and minerals. |
It helps in the conduction of food materials. |
The process of conduction is unidirectional, i.e., from roots to apical parts of the plant. |
The process of conduction is bidirectional, i.e., from leaves to storage organs or growing parts or from storage organs to growing parts of plants. |
The conducting channels are tracheids and vessels. |
The conducting channels are sieve tubes. |
Most of the elements of xylem i.e., tracheids, vessels and fibres are dead in nature. Only xylem parenchyma consists of the living elements. |
Most of the elements of phloem are living in nature i.e., sieve tubes, companion cells and phloem parenchyma. Only phloem fibre are dead elements. |
Xylem also provides mechanical strength to the plant. |
Phloem performs no such function for the plants. |