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GENERAL IDEA ABOUT

PLANT TISSUES

----PRESENTED BY AINDRILA MAJUMDAR[BIOTECHNOLOGY 2nd

YEAR]

TOPICS TO BE DISCUSSED…

- INTRODUCTION- DEFINITION

- CLASSIFICATION- MERISTEMATIC

TISSUE (Types with characterization and

function)

INTRODUCTION THE LIFE OF AN ORAGANISM STARTS FROM A SINGLE CELL, WHICH IS THE FERTILIZED EGG OR THE ZYGOTE. THIS SINGLE CELL UNDERGOES REPEATED MITOTIC DIVISION TO FORM A MULTICELLULAR EMBRYO AND FINALLY THE ORGANISM GRADUALLY DIFFERENTIATES.

THE FORMATION OF A MULTICELLULAR ORGANISM SHOWS THE FOLLOWING ORGANIZATIONAL STAGES, (1)CELLS (2)TISSUE (3)TISSUE SYSTEM (4)ORGAN (5)ORGAN SYSTEM (6)BODY OF AN ORGANISM.

BUT IN UNICELLULAR ORGANISM, ALL THE PHYSIOLOGICAL FUNCTIONS ARE CARRIED OUT BY A SINGLE CELL, SO THIS ORGANIZATION IS NOT OBSERVED.

IN HIGER PLANTS, TISSUE SYSTEMS ARE OF THREE TYPES: (1)EPIDERMAL (2) GROUND (3)VASCULAR.

DEFINITION: A TISSUE IS DEFINED AS A GROUP OF ORGANIZED CELLS WITH A COMMON ORIGIN, FUNCTION AND SIMILAR OR DIFFERENT STRUCTURES.CLASSIFICATION:

On the basis of divisional power of plant tissue, it can be classified into three categories…..1. Meristematic tissue can be

broadly classified on the basis of origin, occurence, function

and division.

2. Permanent tissue can be simple or complex.

3. Special tissue can be broadly classified into external

secretory and internal secretory. It is actually a permanent tissue.

MERISTEMATIC TISSUEThe group of plant cells or tissue which is in the active state of division is called meristematic tissue or meristems. Consists of small, cubodial densely packed cells with thin cell walls & large nuclei, which keeps on dividing to form new cells. Contain small vacuoles and lack intercellular spaces. Capable of stretching, enlarging and differentiate into other types of tissues they mature. Remain young forever & divide actively throughout the life of the plant. Found in shoot & root tip, nodes, buds, between xylem & phloem and so on. Gives rise to permanent tissues.

Meristimatic tissue based on occurance are:1.Apical meristem2. Intercalary

meristem3. Lateral meristem

APICAL MERISTEM Present at the growing regions of the apex of the plant organs. Found at the shoot apex, may also be found at the leaf apices of developing leaves. Forms primary permanent tissue. Also increases the longitudinal growth of plants.

INTERCALARY MERISTEMThe meristematic tissue that remain embedded within the permanent tissue mainly between two nodes. They remain in leaf base or at the lower internodes of growing stem. They are formed because some meristematic zones are left behined by the stem during apical growth.

Functions of intercalary meristem is to intiate lengthwise growth of the plant in addition to the primary meristem. Also forms permanent tissue.

LATERAL MERISTEMPresent laterally on the axis of a plant. Occur longitudinally on the lateral regions of roots and stems mostly in two forms:1. Fasicular cambium: The primary

cambium remaining within the vascular bundles forming the secondary xylem and phloem.

2. Phellogen or cork cambium: They are extraxylary in position, noted during the formation of bark of periderm. They are formed of three layers,the lowermost living layer called phelloderm, cutting off the upper cork cambium or phellogen, which finally forms the outermost scale bark or phellem, that are shedded off from time to time.

MERISTEMATIC TISSUE ON THE BASIS OF ORIGIN

1. PROMERISTEM: PRESENT AT THE GROWING REGIONS OF EMBRYO MAINLY SHOOT OR ROOT TIP OF A GROWING SEEDLING. IT FORMS THE PRIMARY MERISTEM.2. PRIMARY MERISTEM: REMAIN IN MERISTEMATIC STATE THROUGHOUT THE LIFE CYCLE IN A PLANT. PRESENT IN ROOT AND SHOOT APEX OF SEEDLING. INITIATES THE FORMATION OF PRIMARY STRUCTURES IN PLANT.3. SECONDARY MERISTEM: ORIGINATE FROM PRIMARY MERISTEMS. FOUND IN VASCULAR REGION IN FORM OF INTERFASCICULAR CAMBIUM. FORMS ANNUAL RING ALONG WITH FASCICULAR CAMBIUM AND INITIATES CORTICAL SECONDARY GROWTH.

MERISTEMATIC TISSUE ON THE BASIS OF FUNCTION1. PROTODERM:

OUTERMOST MERISTEMATIC LAYER,WHICH BY RADICAL DIVISION FORMS THE EPIDERMAL TISSUE IN THE STEM AND EPIBLEMA OR THE PLIFEROUS LAYER IN ROOT.

2. PROCAMBIUM: GIVES RISE TO VASCULR TISSUES VIZ. XYLEM,PHLOEM AND CAMBIUM OF VASCULAR BUNDLE.

3. FUNDAMENTAL OR GROUND MERISTEM: THE TISSUE LIKE CORTEX, PITH AND MEDULLARY RAYS. OCCURS IN BETWEEN PROTODERM AND PROCAMBIUM. FORMS CORTEX, PITH AND PROCAMBIUM.

MERISTEMATIC TISSUE BASED ON PLANE OF DIVISION

1.PLATE MERISTEM: HERE THE CELL DIVISION TAKES PLACE IN TWO PLANES RESULTING IN THE INCREASE IN AREA. OCCURS ON THE LEAF EPIDERMIS, CORTEX AND PITH. CAUSES AN INCREASE IN AREA OF EPIDERMIS.

2. RIB MERISTEM: HERE THE CELL DIVISION TAKES PLACE IN ONE PLANE. REMAINS IN THE VASCULAR BUNDLES OF ROOT AND STEM. CAUSES INCREASE IN LENGTH OF VASCULAR TISSUES.

3. MASS MERISTEM: DIVIDES IN ALL PLANES INCREASING THE VOLUME OF CELLS. IT REMAINS IN THE ENDOSPERM, CORTEX, PITH. HELPS IN THE FORMATION OF EMBRYO, ENDOSPERM, CORTEX AND PITH. ACTS AS PACKAGING TISSUE SERVING THE PURPOSE OF STORAGE AND PHOTOSYNTHESIS.

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