TOPICSIMPLE TISSUES

“ A simple tissue is made up of similar

type of cells which have common origin

and function”

DEFINITION OF SIMPLE TISSUES

Three types of simple tissues are 1. Parenchyma 2. Collenchyma3. sclerenchyma

TYPES OF SIMPLE TISSUES

Parenchyma is a Greek word Para means “beside”& en means “to pour”

parenchyma tissues is composed of living cells which are variable in their morphology & physiology

1. Parenchyma

It occurs in Pith Mesophyll of leaf Pulp of fruit Endosperm of seed Xylem and Phloem

Occurrence

It consists of unspecialized cells with

thin cell walls these are living, with a large central

vacuole intercellular spaces between them. Oval ,rounded & polygonal in shapes

Structure

Arenchyma

In aquatic plants large air cavities are present which give buoyancy to the plants and help them to float

Types of parenchyma tissuesChlorenchyma

It contains chlorophyll & performs photosynthesis.

1. It provides support to plants and also stores food in the form of starch grains fats & oils

2. Air spaces in parenchyma also facilitate exchange of gases

Functions

They are elongated living cells with small intercellular spaces. Their cell walls are made of cellulose and pectin.

It occur in the peripheral regions of stems and leaves.

It allows easy bending in various parts of a plant (leaf, stem) without breaking.

mature collenchyma are living & contain

protoplast

2.collenchyma( supporting tissues)

structure of collenchyma

Types of collenchyma tissues on the basis of cell arrangement three types are 1.Angular 2.Lamellar3.tubular

1. AngularIn this type cells are irregularly arranged e.g ficus2.LamellarCells are arranged in tagential rows(plate like arrangement) e.g sambucus3. tubularTube like arrangement,intercellular spaces are present

It provides mechanical support and flexibility in plants.

Helps in photosynthesis

Function of collenchyma

The sclerenchyma is a Greek word Sclerous means “hard” & enchyma means “infusion”

3.Sclerenchyma

Sclerenchyma are long, dead cells with a deposit of lignin in their cell wall.

They have no intercellular spaces. This tissue is present in stems, around

vascular bundles, in the veins of leaves and in the hard covering of seeds and nuts.

Thick walled cells Don’t possess living protoplast at

maturity

structure

It provides strength to the plant parts.

it maintain the turgidity of plants

function

Two types are

Fibres Sclereides

Types of sclerenchyma

elongated sclerenchyma cells,usually with pointed end

The wall of fibres are usually lignified Pits of fibres are always small,round,or

silt like At maturity the protoplast disappear &

permanent cells becomes dead or empty

It occurs in patches Average length of fibres is 1to 3mm

1.Fibres

Two types of fibres are

Xylem fibres Extraxylary fibres

Types of fibres

the fibres develop from the same

maristematic tissues as the other xylem cells

orThe fibres which originated from xylem

Xylem fibres

These are related to phloem that form continous cylinder in monocotyledon stem arise in the ground tissue under the epidermis at variable distance

TYPES: 1.Phloem fibres (originating primary &

secondary phloem)2.Cortical fibres ( originating in the cortex)3.Perivascular fibres( originated in the

peripheral region of vascular cylinder

Extraxylary fibres

- Sclerenchymatous cells which are short and possess extremely thick, lamellated, lignified walls with long singular piths. They are called sclerides

Its is commonly found in cortex and pits of gymnosperms

Types:1.Brachysclereids2.Macrosclereids3.Osteosclereids

sclereids

4.Astrosclereids 1.brachysclereids stone cells are short & more or less isodiametric. These are commonly found in cortex ,phloem,& pulp of fruit 2.macrosclereids more or less rod like cells found in

xerophytic leaves

3.osteosclereids theses are bone shaped & found in

the hypodermal layer of seeds & fruits

4.Asterosclereids these are star shaped found in

intercellular spaces of the leaves & stem of hydrophytes