Botany lecture notes

Sclerenchyma: Structure, Classification and Functions with PPT


sclerenchymatous tissue ppt

Sclerenchyma
(Structure, Types and Functions of Sclerenchymatous Cells in Plants)

What are Sclerenchymatous Cells?

Ø  Sclerenchyma is a simple permanent tissue in plants.

Ø  Sclerenchymatous cells are dead at their maturity.

Ø  Cells do not have protoplast when they completely developed.

Ø  They have thick secondary cell wall.

Ø  The secondary cell wall is lignified and very hard.

Ø  Most of the sclerenchymatous cells show intrusive growth.

Different Types of Sclerenchymatous Cells in Plants:

Ø  Based on size, two types of sclerenchyma are described.

  (I).   Sclereids

(II).    Fibres

(I). Sclereids:

Ø  Sclereids are short sclerenchymatous cells.

Ø  They are also called as stone cells.

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Botany lecture notes

Collenchyma Cells in Plants: Structure, Classification and Functions with PPT

Functions of collechyma

Collenchyma
(Structure, Types and Functions of Collenchymatous Cells in Plants)

What is collenchyma?

Ø  Collenchyma is a simple permanent tissue in plants.

Ø  They are living cells with prominent nucleus and all the cell organelles.

Ø  Each collenchymatous cell is with a large and prominent vacuole in the centre.

Ø  The vacuole is filled with many secondary metabolites.

Ø  Unlike parenchyma, the collenchyma cells possess thick primary cell wall.

Ø  Thick walls are NOT lignified.

Ø  The thick wall is due to the deposition of hemicellulose and pectin along with cellulose.

Ø  Wall thickening in collenchyma is greatly affected by the extent of mechanical stress.

Ø  A plant part which in severe stress or motion due to high wind are more likely to possess more thickened collenchyma.

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Botany lecture notes

Parenchyma Cells in Plants: Structure, Classification and Functions (PPT)


functions of parenchyma

Parenchyma
(Structure, Classification and Function of Parenchyma)

What is simple tissue?

Ø  The tissue (a group of cells with particular function) composed of single type of cells.

Ø  Three types of simple tissue system in plants:

(1).  Parenchyma

(2).  Collenchyma

(3).  Sclerenchyma

What are the characteristics of Parenchyma (Parenchymatous Cells)?

Ø  Parenchyma is a simple permanent tissue.

Ø  They are living cells which contains plenty of water.

Ø  Cells are nucleated with prominent nucleus.

Ø  They are thin walled cells.

Ø  Cell wall composed of cellulosic primary cell wall only.

Ø  No lignin deposition in the cell wall of parenchyma.

Ø  Parenchymatous cells are relatively undifferentiated

Ø  Parenchyma is the least specialized along simple permanent tissues in plants.

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Botany lecture notes

P Protein (Phloem Protein): Structure, Classifications and Functions


forisomes definition

P – Protein (Phloem Protein)
(Structure, Classification and Functions of Phloem Proteins)

What are P Proteins? 

Ø  P Proteins (Phloem Proteins) are a category of proteins found in the sap of the sieve tubes of the phloem of Angiospermic plants.

Ø  P-proteins were also as called ‘slime bodies’ of ‘slime’ in the old literature.

Ø  P proteins are usually found in the phloem of dicot plants.

Ø  They are very rarely reported in monocots.

Ø  P proteins are completely absent in the phloem of Pteridophytes and Gymnosperms.

Ø  P proteins occur in different forms in the different developmental stages of sieve tubes.

Ø  P proteins can exist in the sieve tubes as tubular, globular, fibrillar, granular and crystalline forms.

Ø  P proteins are highly polar molecules and they can form gel like substance in the presence of water.

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Botany lecture notes

Complex Tissue System in Plants: Part 2 – Phloem – Structure, Components and Classification (with PPT)


cell types in phloem

Phloem
Structure, Composition & Classification of Primary and Secondary Phloem

What is phloem?

Phloem is a complex tissue system in plants. It is the food conducting tissue of vascular plants. Together with xylem, they form the vascular tissue system. The phloem composed of several types of cells among which some are living cells and some are dead. The term ‘phloem’ was introduced Nageli (1853) from a Greek word ‘phloios’ meaning ‘bark’. The ‘bark’ is a non-technical term describing all tissue outside the secondary xylem of the plant. Botanically the bark includes secondary phloem, cortex, primary phloem and periderm. The current post describes the structure, composition and classification of phloem.

Location of phloem in plants:

Ø  Usually, the phloem is situated external to xylem.

Ø  In leaves, the phloem is located on the abaxial side (lower side).

Ø  In some plants (members of Cucurbitaceae and Convolvulaceae), the phloem is present on both external and internal to xylem. Such a vascular bundle is called bicollateral vascular bundle.

Ø  Phloem present internal to the xylem is called ‘internal phloem’ or intra-xylary phloem.

Ø  Phloem located external to the xylem is called ‘external phloem’.

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