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GYMNOSPERMS INTRODUCTION GYMNOSPERMS INTRODUCTION

GYMNOSPERMS INTRODUCTION - PowerPoint Presentation

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GYMNOSPERMS INTRODUCTION - PPT Presentation

Gymnosperms Gymno naked sperma seed include simpler and primitive plants They are characterised by the presence of naked ovules borne unprotected on the surface of the megasporophylls ID: 755854

leaves male cone strobili male leaves strobili cone gymnosperms called pinus female ovules cones reproduction cycas seeds microsporophylls roots pollen plant stem

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Slide1

GYMNOSPERMSSlide2

INTRODUCTION

Gymnosperms (

Gymno

: naked,

sperma

= seed

) include simpler and primitive

plants.

They are

characterised

by the presence of

naked ovules

, borne unprotected on the surface of the

megasporophylls

.

Gymnosperms are sometimes called as

phanerogams

without ovary

.Slide3

GENERAL CHARACTERISTICS

Most

of the living gymnosperms are evergreen trees or shrubs with

xerophytic

 adaptation. 

The main plant body is

sporophytic

and is differentiated into root, stem and leaves

.

The stem is usually erect, profusely branched (

Unbranched

in 

Cycas

) and woody

. Sometimes

, as in 

Zamia

, it is

tuberous.

Presence

of

leaf scars

on the stem is a characteristic feature of gymnosperms.Slide4

GENERAL CHARACTERISTICS

The

plant possess well developed

tap root

system.

Roots

of some have

symbiotic relationship with blue green algae (Coralloid roots of Cycas) or fungi (e.g. mycorrhizal roots of Pinus).Slide5

GENERAL CHARACTERISTICS

CYCAS PINUS

ZAMIA Slide6

LEAVES

The leaves are usually

 dimorphic

The foliage leaves are

green, simple, needle shaped or

pinnately

compound.Scaly leaves are usually minute and deciduous.The leaves are well adapted to withstand extremes of temperature, humidity and wind due to following features. -Needle like leaves reduces surface area.

-Thick cuticle.

-Sunken stomata.Slide7

LEAVESSlide8

REPRODUCTION

Main plant body is

sporophyte

and

heterosporous

. It

produces

haploid microspores and megaspores.The spores are produced in sporangia that are born on sporophyll.The sporophylls are arranged spirally along an axis forming compact strobili

or cones

.

The male and female cones or

strobili

may be borne on the

same tree (

Pinus

)

or on

different trees(

Cycas

).

Strobili

bearing

microsporophylls

and

microsporangia

are called male

strobili

or male cone.Slide9

STROBILISlide10

REPRODUCTION

MALE

CONE (STAMINATE CONE)

Male cones are usually short-lived.

Microsporangia

develop on the

abaxial

side of the microsporophylls. The number of sporangia persporophyll varies from two  to many.Microspores develops into a male gametophyte generation which is much reduced and is confined to only a limited number of cells..This reduced gametophyte is called a pollen grain.Development of pollen grains takes place within the micrsporangia.

FEMALE

CONE (OVULATE CONE)

The

cones bearing

megasporophyll

with

megasporangia

(ovules) are called as female cone.

In

megasporangia

, the mega spore mother cell divides

meiotically

to form four haploid megaspores. 

One of the megaspore develops into a

multicellular

female

gamerophyte

that bears two or more archegonia.Slide11

REPRODUCTIONSlide12

REPRODUCTION

Strobili

bearing

microsporophylls

and

microsporangia

are called male

strobili or male cone.The pollen are released from the microsporangium and are carried with air current to the ovules. After fertilization, zygote develops into embryo and ovules into seeds. The seeds are naked.Slide13

LIFE CYCLE OF 

PINUSSlide14

ECONOMIC IMPORTANCE

Edible

seeds

Ornamental

Timber

Paper

Drug- Ephedrine

Fibre boardEssential oilResins- Turpentine