BIOLOGY
Vessels or Trachaea: Cells are broad and short, placed end to end to form a continuous hollow tube. Water and waterdissolved minerals are conducted from root to leaf by these cells.
Xylem fibre: These are sclerenchymatous cells. Their main function is to give mechanical strength to the plant.
Xylem parenchyma: These are parenchymatous . cells. Functions of these cells are storage and conduction of food materials.
Functions of xylem tissue: Their functions are to give mechanical strength to the plant body, conduction of water, minerals and food materials and storage of food. Phloem tissue: Phloem tissue consists of four types of cells, namely: sieve tubes, companion cells, phloem fibres and phloem parenchyma.
Sieve tube: These are elongated hollow cells placed end-to-end forming a long tube. The partition walls between two adjacent sieve cells are perforated and known as sieve plate. In m4;iture sieve tube there is. no nucleus in the cell. Conduction of food, prepared in the leaves is its main function.
Companion cells: These are parenchymatous, narrow, elongated cells, and are closely associated with the sieve tube. They have dense cytoplasm and a large nucleus. Conduction with the sieve tube is done through the pores present on the walls of these cells. They help the sieve tubes in conduction of food materials.
Phloem fibre: These are Sclerenchymatous cells. They are also known as bast fibre. Its function is to give mechanical strength. Phloem parenchyma: These are parenchymatous cells. They help in storage and conduction of food materials. Function of Phloem tissue: There main function is to conduct food materials, prepared in the leaves, to different parts of the plant. They give mechanical strength to plant organ. In case of necessity they store food materials.
Importance of Complex tissues: In respect of physiological and economic aspects, complex tissues are of great importance. Physiological importance: Complex tissues perform the duty of conduction of raw food materials to leaves and prepared food materials to all the living cells. Beside preparation of food, water is necessary for various reactions. This water is conducted from root to stem through the complex tissue named xylem. Through xylem tissue dissolved minerals along with water also passes upwardly. Water used in transpiration also moves to leaf through xylem tissue.
Economic importance
The most important economic crop in Bangladesh is jute fiber. Jute fiber is the secondary phloem or bast fiber. The wood we use, in the construction of houses, in making furniture, boat or musical instruments or as fuel, is the secondary xylem
Secretoy tissues are those tissues, which secrets various liquids, Resins, gums, rubber etc. are collected from secretory tissues. They are of two types: . Laticiferous tissues and Glandular tissues. Laticiferous tissue: Latex is a white, yellow or colourless liquid Carbohydrates, protein, gums, and fats etc. are mixed in Latex, Latex is found in various plants like;- Musa (KALA) Ficus (BOT), Hevea (RUBBER), Papiver (OPIUM), Calotropis (AKONDO), Alstonia (CHHATIM), Argement (SHIALKATA). Glandular tissue: Honey, Enzymes, Gums, Resins, Oils etc. are usually found in the glandular tissues.
i) Epidermal Tissue System: - This tissue system makes the outer cover of plant organs like, roots stems, branches, leaves, fruits. etc. Typically it consists of a closely arranged single layer of parenchymatous cells. There may have unicellular or multicellular hairs. Functions: To give protection to the internal portion of the plant organ.
ii) Ground Tissue System : Theses are the main bulk of tissues of roots and stems. The ground tissue is differentiated into outer cortical region and inner medulla or pith region. In dicot stem the cortical region is ususlly subdivided into three zones namely:- (a) Hypodermis, (b) General, Cortex and (c) Endodermis, Medulla anHypodermis, (b) General,Cortex and (c) Endodermis,Medulla and Medullary Raysd Medullary Rays encircled by, the Pericycle form the central Pith.
Functions : Functions of this tissue system are to give mechanical stregth to the stem and to store food materials.
iii) Vascular Tissue System:- Vascular tissue system comprises of two complex tixssue, namely; Xylem and phloem, These tissues are embedded in the ground tissues. In dicotyledonous stems xylem and phloem lie side by side on the same radius and between them there is a kind of Meristamatic tissue named Cambium. Phloem tissue lies towards the periphery and xylem toward center of the stem. Arrangement of different tissue system of a dicot stem is shown In longitudinal (I.S.) and transverse section (T.S) [Gig: -4.8 & 4.9]
Function Conduction of water and dissolved food materials. Conduction of prepared food. Give mechanical strength to the stem, and Storage of food where necessary. 
Excercise
Multiple choice questions
1. Which one has Aerenchyma?
a. in Murtha grass
b. in Lily
c. in Bamboo
d. In Guava
2. In case of permanent tissue
i. The cell wall is comparatively thick
ii. The cell has vacuole
iii. The cytoplasm of the cell is thick. Which one of the following is correct?
a. i
b. ii
c. i & ii
d. i, ii & iii
Give answer to the question no 3 & 4 on the basis of the following diagram.
3. In the diagram what is part labelled A?
a. Permanent tissue
b. Meristamatic tissue
c. Xylem tissue
d. Phloem tissue
4. For the part labelled A in the diagram the plant-
a. stem increases in girth
b. stem increases in length
c. root increases in girth
d. root increases in length. Creative Questions
Bacteria, Amoeba and other living beings do not have tissues but Man, Mangoes, Berry etc. have tissues. The tissues are again of two types: Meristematic tissue and Permanent tissue. A part of the transverse section of stem of Dicot plant is shown below.
a. What is meristamatic tissue?
b. Why bacteria do not have tissues explain.
5. Explain the function of the part B after drawing its labelled diagram.
6. Analyse the cause of creation of above B & C tissues in a mango tree.
complex plant tissues
Tracheids: Cells are dead, long with transverse ends, containing large vacuole. Cell walls are hard, strong. and lignified. Their main functions are to give mechanical strength and to supply water and dissolved minerals from root to the leaves.Complex tissue is composed of more than one kind of cells. They are two types, namely Xylem tissue and Phloem tissue.
 |
| Tracheid |
Xylem tissue: Xylem tissue consists of four types of cells, namely: Tracheids, Vessels or Trachaea, Xylem fibre and Xylem Parenchyma.
 |
| Vessel |
Xylem fibre: These are sclerenchymatous cells. Their main function is to give mechanical strength to the plant.
Xylem parenchyma: These are parenchymatous . cells. Functions of these cells are storage and conduction of food materials.
Functions of xylem tissue: Their functions are to give mechanical strength to the plant body, conduction of water, minerals and food materials and storage of food. Phloem tissue: Phloem tissue consists of four types of cells, namely: sieve tubes, companion cells, phloem fibres and phloem parenchyma.
 |
| Phloem tissue |
Sieve tube: These are elongated hollow cells placed end-to-end forming a long tube. The partition walls between two adjacent sieve cells are perforated and known as sieve plate. In m4;iture sieve tube there is. no nucleus in the cell. Conduction of food, prepared in the leaves is its main function.
Companion cells: These are parenchymatous, narrow, elongated cells, and are closely associated with the sieve tube. They have dense cytoplasm and a large nucleus. Conduction with the sieve tube is done through the pores present on the walls of these cells. They help the sieve tubes in conduction of food materials.
Phloem fibre: These are Sclerenchymatous cells. They are also known as bast fibre. Its function is to give mechanical strength. Phloem parenchyma: These are parenchymatous cells. They help in storage and conduction of food materials. Function of Phloem tissue: There main function is to conduct food materials, prepared in the leaves, to different parts of the plant. They give mechanical strength to plant organ. In case of necessity they store food materials.
Importance of Complex tissues: In respect of physiological and economic aspects, complex tissues are of great importance. Physiological importance: Complex tissues perform the duty of conduction of raw food materials to leaves and prepared food materials to all the living cells. Beside preparation of food, water is necessary for various reactions. This water is conducted from root to stem through the complex tissue named xylem. Through xylem tissue dissolved minerals along with water also passes upwardly. Water used in transpiration also moves to leaf through xylem tissue.
Economic importance
The most important economic crop in Bangladesh is jute fiber. Jute fiber is the secondary phloem or bast fiber. The wood we use, in the construction of houses, in making furniture, boat or musical instruments or as fuel, is the secondary xylem
Secretory tissue:
 |
| Tissue |
Tissue System
When one or more kinds of tissues are united and together perform a similar function, then it is known as tissue system. They are classified into three types namely: i) Epidermal Tissue System, ii) Ground Tissue System and iii) Vascular Tissue System.i) Epidermal Tissue System: - This tissue system makes the outer cover of plant organs like, roots stems, branches, leaves, fruits. etc. Typically it consists of a closely arranged single layer of parenchymatous cells. There may have unicellular or multicellular hairs. Functions: To give protection to the internal portion of the plant organ.
ii) Ground Tissue System : Theses are the main bulk of tissues of roots and stems. The ground tissue is differentiated into outer cortical region and inner medulla or pith region. In dicot stem the cortical region is ususlly subdivided into three zones namely:- (a) Hypodermis, (b) General, Cortex and (c) Endodermis, Medulla anHypodermis, (b) General,Cortex and (c) Endodermis,Medulla and Medullary Raysd Medullary Rays encircled by, the Pericycle form the central Pith.
Functions : Functions of this tissue system are to give mechanical stregth to the stem and to store food materials.
iii) Vascular Tissue System:- Vascular tissue system comprises of two complex tixssue, namely; Xylem and phloem, These tissues are embedded in the ground tissues. In dicotyledonous stems xylem and phloem lie side by side on the same radius and between them there is a kind of Meristamatic tissue named Cambium. Phloem tissue lies towards the periphery and xylem toward center of the stem. Arrangement of different tissue system of a dicot stem is shown In longitudinal (I.S.) and transverse section (T.S) [Gig: -4.8 & 4.9]
Function Conduction of water and dissolved food materials. Conduction of prepared food. Give mechanical strength to the stem, and Storage of food where necessary. Excercise
Multiple choice questions
1. Which one has Aerenchyma?
a. in Murtha grass
b. in Lily
c. in Bamboo
d. In Guava
2. In case of permanent tissue
i. The cell wall is comparatively thick
ii. The cell has vacuole
iii. The cytoplasm of the cell is thick. Which one of the following is correct?
a. i
b. ii
c. i & ii
d. i, ii & iii
 |
| Fig1 |
3. In the diagram what is part labelled A?
a. Permanent tissue
b. Meristamatic tissue
c. Xylem tissue
d. Phloem tissue
4. For the part labelled A in the diagram the plant-
a. stem increases in girth
b. stem increases in length
c. root increases in girth
d. root increases in length. Creative Questions
 |
| Fig 2 |
a. What is meristamatic tissue?
b. Why bacteria do not have tissues explain.
5. Explain the function of the part B after drawing its labelled diagram.
6. Analyse the cause of creation of above B & C tissues in a mango tree.
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