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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Botany lecture notes

Tyloses: Definition, Structure and Functions


tyloses definition

Tyloses

What are Tyloses?

Tyloses (singular – tylosis) are the balloon like outgrowth of parenchymatous cells to the lumen of tracheids or vessels of the secondary xylem. The axial and ray parenchyma of the xylem develops protrusion and these protrusions enter or invade into the lumen of tracheids or vessels through pits. This invasion of parenchyma occurs when tracheids or vessels become inactive or damaged.

Who discovered Tyloses?

Malpighi (1686) for the first time reported the ‘balloon-shaped sacs’ in the lumen of vessels of heartwood and he named it as tyloses based on the Greek word ‘Thyllen’ meaning ‘bag’ or ‘container’.

How Tyloses are Formed?

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Botany lecture notes

Complex Tissue Systems in Plants: Part-1 Xylem – Structure, Components and Classification (with PPT)


cell types in xylem

Xylem
(Structure, Composition & Classification of Primary and Secondary Xylem)

What is vascular tissue?

The tissue associated with conduction of water, minerals and food materials in plants are called vascular tissue. Plants with a well-developed conductive system are thus called as ‘vascular plants’. Vascular plants are also known as ‘Tracheophyta’ (‘trachaea’ = vessels, a component of xylem, ‘phyta’= plants).

The vascular systems in plants composed of two types of tissues

(1). Xylem: Tissue for the conduction of water and minerals.

(2). Phloem: Tissue for the conduction of food materials.

Learn more: Difference between Xylem and Phloem

Both the xylem and phloem are complex tissues composed of more than one types of cells.  Xylem and phloem are closely organized in plants. The vascular bundles found in the primary structures of plants are formed by the association of xylem and phloem.

What is xylem?

The xylem is one of the conductive tissues in plants. It is a complex tissue composed of many types of cells. The term xylem was proposed by Nageli (1858) and he derived the word from a Greek word ‘xylos’ meaning wood. The main function of xylem is to conduct water and minerals from roots to leaves. The secondary xylem also provides mechanical support due to the presence of thick lignified cell wall.

What are the components or elements of xylem?

The xylem composed of four types of cells. Among these cells, some cells are living and some are dead.

The four elements of xylem are:

(1).  Tracheids

(2).  Vessels

(3).  Xylem Fibres

(4).  Xylem Parenchyma

(1). Tracheids

Tracheids are the fundamental cell type in the xylem. They are elongated tube like cells with tapering ends and chisel like in appearance. The cells are non-living at their maturity and the mature cells are empty without protoplast. They have highly lignified secondary cell wall and the cells angular and polygonal in cross section. The average length of tracheid is 5 – 6 mm. Major portions of the cell wall of tracheids are perforated with pits. They also possess pit pairs between two adjacent tracheids at their common walls. Pits may be simple circular pits or advanced bordered pits.

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Free Net Life Science Study Materials

CSIR JRF NET Life Sciences December 2016 Original Solved Question Paper (Download PDF)


csir net december 2016 answer key

CSIR JRF NET Life Sciences December 2016 Solved Question Paper PDF

Official / Original Previous Year (Old) Solved Question Paper of CSIR Junior Research Fellowship (JRF) and National Eligibility Test (NET) Life Sciences (XL) Examination Dec 2016  with Answer Key and Explanations as PDF. CSIR aspirants can download the question paper as single PDF file for your exam preparation. To download the question paper as single PDF file, please click on the download button below. Feel free to ask any doubts or clarifications.

To download the question paper as a single PDF file, please click on the link below.

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Botany lecture notes

Difference between Parenchyma and Collenchyma: A Comparison Table


collenchyma vs parenchyma

Parenchyma vs Collenchyma
(Similarities and Differences between Parenchyma and Collenchyma)

Parenchyma and Collenchyma are the Simple tissue System in Plants. The present post describes the similarities and differences between PARENCHYMA and COLLENCHYMA.

Similarities between Parenchyma and Collenchyma

Ø  Both parenchyma and collenchyma are simple permanent tissues in the plants.

Ø  Both are differentiated cells.

Ø  Both are living cells with primary cell wall.

Ø  Both cells possess cytoplasm and cell organelles including the nucleus.

Ø  Both are the components of ground tissue system in plants.

Ø  Both cells can do photosynthesis if chloroplasts are present in them.

Ø  Both can store food materials as starch grains.

Ø  Pits are absent in the cell wall of both parenchyma and collenchyma.

Ø  Plasmodesmatal connections between cells occur in both cells.

Differences between Parenchyma and Collenchyma

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