BIOLOGY CHAPTER-1 PLANT TISSUESmetasofsda.in/.../sites/4/2020/04/Biology-Chapter-1-Plant-Tissues.pdf · The tissues that are completely grown and has lost the ability of division

BIOLOGY

CHAPTER-1 PLANT TISSUES

Overview of the types of plant tissues being studied in this chapter.

The diagram above depicts how several cells adapted for the same function work in conjunction to form tissues.

Tissue:

A tissue is a group of cells, similar in structure that work together to perform specific function. Different types of plant tissues include permanent and meristematic tissues.

Meristematic tissue:

These tissues have the capability to develop by active division. They assist in the major growth of the vegetation. Growth in length and growth in diameter of the plant are carried about by these cells. The Meristematic cells are cubical, thin living cells with a big nucleus made up of cellulose. These cells are compactly arranged with no intercellular spaces. Depending on the section where the meristematic tissues are existing, they are categorized as meristems intercalary, lateral and apical.

1. Apical meristem is existent at the growing tips or apical of stems and roots. Apical meristem brings about elongation of the stem and root.

2. Lateral meristem is existent in the radial portion of the stem or root. Lateral meristem increases the diameter of the plant organs.

3. Intercalary meristem is found at the internodes or at the base of the leaves. Intercalary meristem increases length of the plant organs.

Old meristematic cells lose the capability to distribute and convert into permanent tissues. This procedure of capturing up a permanent function, size, and shape is termed as differentiation.

Permanent Tissue:

The tissues that are completely grown and has lost the ability of division are known as permanent tissues. The meristematic tissues divide and differentiate to form the permanent tissues.

Types of Permanent Tissue

Simple Permanent Tissue:

These are also known as homogenous tissues. They are made up of a single cell type, usually with the same origin, structure, and function.

Simple permanent tissue is further classified into three types:

Parenchyma

• The cells have an oval or round shape.

• The cell wall is made up of hemicellulose or cellulose.

• The cell is thin-walled.

• The cells have vacuoles and very small nucleus.

• It is found in all parts of the plant.

• The protoplasm is living and dense.

Modified types of Parenchyma:

Chlorenchyma is a special type of Parenchyma tissue. It is special, because it contains chlorophyll- the green coloured pigment that is responsible for photosynthesis. All cells in parenchyma have similar function as it is a simple permanent tissue, hence all cells in chlorenchyma, apart from filling bulk space, performs an additional task of photosynthesis.

Aerenchyma is a modified parenchyma, where the cells are arranged with regular air spaces or air chambers to facilitate diffusion of gases to provide buoyancy to aquatic plants such as lotus and water hyacinth.

Collenchyma

• Cells are long and thick walled.

• The cell wall is made up of cellulose and pectin.

• It is the only tissue with the highest refractive index due to the presence of pectin.

• It is found in hypodermis of dicot stem and the vascular bundle of dicot leaf.

• The amount of chloroplast is less in the cells.

• The cells have no intercellular spaces.

Sclerenchyma

• These are dead tissues, very hard and rigid in texture.

• Cells are thick walled with various size and shapes.

• These provide mechanical support and rigidity to the plant.

CROSS SECTION OF PARENCHYMA, COLLENCHYMA AND SCLERENCHYMA.

DIFFERENCE BETWEEN PARENCHYMA, COLLENCHYMA AND SCLERENCHYMA

Complex permanent Tissue

The complex tissues are made up of different types of cells performing diverse functions. These are of two types:

Xylem

• It transports water and nutrients from the roots to the leaves of the plant.

• It provides support to the plants.

• It is divided into-tracheids, vessels, xylem fiber, and xylem parenchyma.

Phloem

• It translocates the prepared organic food from the leaves to different parts of the plant.

• It is also known as bast.

• It is composed of sieve tubes, companion cells,phloem parenchyma and phloem fibers.

Difference between xylem and phloem

WORK SHEET Fill in the blanks

1. A group of cells similar in structure that work together to perform

a particular function forms a _________.

2. The cells of ________ tissue have thin cellulose cell walls.

3. The _______ cells in plants are compactly arranged and do not

contain any intercellular space between them.

4. __________ tissues of plants are growth tissues.

5. ___________ meristem situated at growing tip of stems and

roots.

6 The main function of ________ tissue in plant is to continuously

form a number of new cells.

7. _________ meristems bring about the elongation of root and

stem.

8. _________ meristem causes the organ to increase in diameter.

9. __________ meristem produces an increase in a length of organ.

10. _________ tissues are derived from meristematic tissues.

11. If air cavities are present, the parenchyma tissue is called

________.

12. The ___________ of simple plant tissue intercellular space are

generally absent.

13. The walls of _______ are greatly thickened with deposition of

lignin.

14. The main function of __________ is to carry mineral salts

upward from the root to different parts of the shoot.

15. The main function of __________ is to carry food from the

leaves to all the parts of the plant.

Question 2: Choose the best: 1. The Actively dividing tissues are also known as: A. Permanent tissue B. Meristematic tissue C. Complex tissue

2. The tissues that are originated from meristematic tissues are called A. secondary tissues B. intercalary tissues C. Permanent tissues 3. The type of support tissues that consists of uneven thickened primary walls with elongated cells is called A. collenchyma's tissues B. phloem tissues C. xylem tissues

4. When parenchyma cells contain chloroplast, they are known as

_______.

A. Collenchyma

B. Chlorenchyma

C. Sclerenchyma

5. Xylem and Phloem come under ________ tissue.

A. simple permanent tissue

B. complex permanent tissue

C. meristematic tissue

TRUE OR FALSE

1. Meristematic tissues are small and thin walled.

2. Permanent tissues are located on the growing tips of roots, stem

and leaves.

3. Cells of parenchyma tissue are dead, thin walled with small

vacuoles.

4. Permanent tissues are actively dividing in nature.

5. Collenchyma tissue provides mechanical strength to the stem.

Video link

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