Chapter-6. Tissues Science class 9 in english Medium CBSE Notes

(B) Complex permanent Tissue:

Complex tissues are made of more than one type of cells, e.i consist of different type of cells. All these cells coordinate to perform a common function.

E.g : xylem and phloem etc.

• They are both xylem and phloem conducting tissues and constitute a vascular bundle.
• Vascular or conductive tissue is a distinctive feature of the complex plants, one that has made possible their survival in the terrestrial environment.

1. Xylem

Xylem is a conducting tissue and constitute a vascular bundle. Xylem consists of tracheids, vessels, xylem parenchyma and xylem fibres. 

Forms vascular bundles with phloem and gives mechanical strength to plant due to presence of lignin cells. 

Function of xylem: 

(i) The xylem carries water and minerals obtained from the soil by roots to the other parts plant.

(ii) It is also responsible for supporting the plant as well as storage and long-distance transportation of water and nutrients from root to other parts. 

(iii) Xylem transports materials unilaterally. 

(iv) It also provides mechanical strength to the plants. 

Elements of xylem: 

(i) Tracheids: These are conducting elements. 

(ii) Vessels : These are also conducting elements. 

(iii) Xylem parenchyma 

(iv) Xylem fibres

Dead Cells: Vessels, tracheids and xylem fibres. 

Live cells: Xylem parenchyma. 

• Conducting and tracheary elements are usually dead. 

2. Phloem: 

Phloem is also a conducting tissue and constitutes a vascular bundle. Phloem is made up of four types of elements: sieve tubes, companion cells, phloem fibres and the phloem parenchyma. 

Function of phloem: 

(i) Phloem transports products of photosynthesis from the leaves where they are synthesized to other parts of the plant. 

(ii) Phloem can move unlike materials of xylem in both directions. 

(iii) Phloem has no mechanical function. 

Elements of phloem:

(i) Sieve tubes : Sieve tubes are tubular cells with perforated walls.

(ii) Companion cells : These are living cells. 

(iii) Phloem fibres

(iv) Phloem parenchyma 

Dead Cells: Phloem fibres 

Live cells: Sieve tubes, Companion cells and Phloem parenchyma. 

• Conducting cells are living. 

Translocation: Transportation of food and nutrients such as sugar and amino acids from leaves to storage organs and growing parts of plant. This movement of substances is called translocation.

Differences between xylem and phloem: