EWING CHRISTIAN

COLLEGE

[AN AUTONOMOUS COLLEGE OF ALLAHABAD UNIVERSITY]

M.Sc previous year

First Semester

Classification of

GYMNOSPERM

By- CHETNA SHUKLA

Introduction• Gymnosperms are woody seed-bearing plants differing

from the other group of seed plants.

• The term "gymnosperm" comes from word

gymnospermos, meaning "naked seeds", after the

unenclosed condition of theirseeds (called ovules in their

unfertilized state).

• There are between 700 and 900 extant* or currently

living species of Gymnosperms.

• They grow in xerophytic conditions and posses

xerophytic adaptations.

• Gymnosperms are heterosporous which means that

they produce different male and female spores. The

microspores develop into pollen grainsand the

megasporesare in an ovule

• .

• Male and female reproductive structures are borne on

sporophylls, scales, or comparable structures

• Most of them are trees and some are shrubs. There are

no herbs..

• They have monopodial growth represented by one main

axis. As the axis grows taller it increases in diameter due

to secondary growth. Stem branches are of two types: 1.

Long shoots or branchesof unlimited growth. 2. Dwarf

shoots or branchesof limited growth.

• The plants possess well-developed tap root system. In

some cases the roots are symbiotically associated with

algae (coralloid roots of Cycas) or with fungi (mycorrhizal

roots of Pinus).

Classification

• Gymnosperms include a number of fossil and living

forms. They include the primitive members of the

Spermophyta (seed- bearing plants) and form a link

between the Pteridophyta on the one hand and the

angiosperms on the other. Various attempts have been

made by different workers to classify the Gymnosperms.

• One of the earliest attempts was made by Bentham and

Hooker (1866-1883), when they divided seed bearing

plants into Dicots, Gymnosperms and Monocots.

Gymnosperms were further divided into Cycadaceae,

Gnetaceae and Coniferae. Engler (1885) divided

Gymnosperms into seven groups as follows: 1.

Cycadofilicales 2. Cycadales 3. Bennittitales 4.

Cordaitales 5. Ginkgoales 6. Coniferales 7. Gnetales

• Coulter and Chamberlain (1917) adapted Engler’s system

with slight modifications and divided gymnosperms into seven

orders: Cycadofilicales, Cycadales, Bennittitales, Cordaitales,

Coniferales, Ginkgoales and Gnetales. He further divided

order Coniferales into two families (Pinaceae and Taxaceae)

and six sub-families as follows:

• Orders Families Sub-families

• Cycadofilicales

• Cycadales

• Bennittitales

• Cordaitales

• Coniferales Pinaceae Abietineae, Taxodineae, Cupressineae ,

• Araucarineae

• Taxaceae Taxineae, Podocarpineae

• Ginkgoales

• Gnetales

• Depending upon the composition of wood, Seward

(1919) divided gymnosperms into two classes: i)

Manoxylic with loose textured and porous wood, and

ii) Pycnoxylic with compact wood. Orders Cycadales,

Cycadeoidales and Cycadofilicales were included in the

former whereas, the latter included the orders

Cordaitales, Ginkgoales, Coniferales and Gnetales.

• Prof. Birbal Sahni (1920) classified gymnosperms into

two divisions depending upon the axial or foliar origin of

the ovules. These are: i) Stachyspermae – in which the

ovules arise on the axial organs, and ii)

Phyllospermae – in which the ovules are borne on

leaves. Stachyspermae was further divided into four

orders and Phyllospermae into three orders as follows:

• Divisions Orders

• Stachyspermae Cordaitales, Coniferales

• Ginkgoales, Gnetales

• Gymnosperms

Phyllospermae Cycadofilicales, Bennittitales

• Cycadales

• Chamberlain (1934) however, divided the gymnosperms into two large

groups A. Cycadophyta and B. Coniferophyta.

• In the Cycadophyta, sporophylls are in cones.

• They include three orders:

• Cycadofilicales (Pteridospermae)-extinct

• Bennettitales (Cycadeoideales)-extinct

• Cycadales-Mesozoic to present day.

• The Coniferophyta is divided into four orders:

• Ginkgoales-Palaeozoic to present day.

• Cordaitales-extinct

• Coniferales-Palaeozoic to present day

• Gnetales-Recent.

• Raizada and Sahni (1938) have summarized the

classification of gymnosperms as follows:

• Cycadophytes:

• Pteridospermae (Cycadofilicales)-Carboniferous. Extinct.

• Cycadeoideales (Bennettitales)-Mesozoic. Extinct.

• Cycadales-Mesozoic to present day.

• Pentoxylales: Jurassic

• Coniferophytes:

• Cordaitales-Palaeozoic. Exinct

• Ginkgoales-Palaeozoic to present day.

• Coniferales-Palaeozoic-Mesozoic to present day

• Gnetales-Recent.

• Chamberlain (1935) classified gymnosperms into:

•

•

Gymnosperms with profusely

branched trunks, leaves simple

(needle-like, scale-like or

laminate), stems with small pith

and cortex. Secondary xylem

cylinder massive and less

parenchymatous (pycnoxylic

wood). The group includes extinct

as well as extant orders like

Gymnosperms with fern-like pinnatifid

leaves, weakly branched large globose

or columnar trunks, having large

conspicuously developed pith and

cortical zones in stem. Secondary xylem

cylinder small, composed mainly of

tracheids and abundant parenchyma

(manoxylic wood). Group well

represented in fossil record. The only

surviving representatives are the modern

cycads.

Orders 1. Cycadofilicales 2.

Bennettitales 3. Cycadales Orders: 1. Cordaitales 2. Voltziales 3.

Coniferales 4. Ginkgoales 5. Gnetales

ConiferophytesCycadophytes

Gymnosperms

• In 1957 prof. D.D PANT gave the modification of

Arnold`s classification and gave the following system..

Cycadophyta Chlamydospermophyta Conifrophyta

CLASS-1-

Pteridospermopsida

Orders-

Lygniopteridales

Medullosales

Glossopteridales

Peltaspermales

Corystospermales

Caytoniales

CLASS-2-

Cycadopsida

Orders-

Cycadales

CLASS-3-

Pentaxylopsida

Orders-

Pentoxylales

CLASS-4-

Bennettitopsida

Orders-

Bennettitales

CLASS-1-

Gnetopsida

ORDERS-

Gnetales

Welwitschiales

CLASS-1-

Coniferopsida

Orders-

Corditales

Coniferales

Ginkgoales

CLASS-2-

Ephedropsida

Orders-

Ephedrales

CLASS-3-

Czekanowskiales

Orders-

Czekanowskiales

CLASS-4-

Taxopsida

Orders-

Taxales

• Kramer & Green (see Kubitzki, 1990) have classified the

Division Gymnosperms into two Subdivision as

• follows:-

•Cycadophytina Coniferophytina

Classes-

Cycadatae

Order-

Cycadales

Families-

1.Stangeriaceae

2.Boweniaceae

3.Cycadaceae

4.Zamiaceae

Classes-

Gnetatae

Orders-

Gnetales

Families-

1.Ephedrac

eae

2.Gnetacea

e

3.Welwitsc

hiaceae

Classes-

Ginkgoatae

Order-

Ginkgoales

Families-

1.Ginkgoace

ae

Classes-

Pinatae

Order- Pinales

(Coniferales)

Families-

1. Taxaceae

2.Cephalotaxaceae

3.Phyllocladaceae

4. Podocarpaceae

5. Araucariaceae 6.

Sciadopityaceae 7.

Taxodiaceae

8.Cupressaceae 9.

Pinaceae

Flow charts showing classification by

different workers:-

• The modern gymnosperms are commonly grouped

under four orders:

• 1. Cycadales;

• 2. Ginkgoales;

• 3. Coniferales and

• 4. Gnetales

• The Cycadales and the Ginkgoales include living

members which have a long, fossil history and can be

regarded as ‘living fossils’. Ginkgoales in the past (early

Mesozoic) were represented by widely distributed group

of plants, but now the order is represented by a single

species Ginkgo biloba.

• The Coniferales from the most conspicuous order of the

living gymnosperms and include the plants like Pinus,

Cedrus, Abies, Juniperus, Cupressus, Biota, etc.

• The Gnetales are represented by three living genera,

e.g., Gnetum, Ephedra and Welwitschia.

Living Gymnosperms

Cycads

GnetophytesGinkgoes

Conifers

•

• The trees are branched,woody and perennial.

• The leaves are dimorphic scaly and foliar.

• Tap root system mostly associated with fungi

[mycorrhizal association]

• Reproductive structures are formed on leaves which

arrange to form cones male and female cones are

formed sepratly.

• Pollen grains are wind spread and embryo formed is di

to polycotylednous

The Largest and the

Oldest Plants are

both Conifers

• Bristlecone pines of the California White Mountains are the oldest

Giant Sequoias of

the California

Sierras are the

largest

Thing on

Earth"

- General

Sherman

-

Sequoia

National

Forest, CA

2200 years old , 275 feet tall ,

30 feet in diameter at the base.

119.3 miles of 1X12 planks

There are seven living families of

Conifers

Norfolk Island Pines

Junipers and CedarsYew

Sequoias and Redwoods

Pines, Fir Spruce

Five of

the most

familiar

• The division coniferophyta contain following 7-families.

• PINACEAE

• It is composed of 10 genera Cedrus, Pinus, Cathaya,

Tsuga,Abies etc.

• Tall and well branched trees.

• Posses dwarf and long shoot

dwarf shoot posses scaly and

needle like foliar leaves.

Taxodiaceae

• Comparises evergreen or deciduous trees and plant

parts are mostly spirally arranged.

• Both male and female cones are arranged on same

plants.

• Contain ovuliferous scales with 2 to 9 ovules on each.

• Pollen grains are wingless and lack prothalial cells.

• Seeds may be winged or wingless or irregular in shape.

• Consist of…. Taxodium, Sequoia,

Sequoiadendron, Taiwania, Cunninghamia

etc.

Cupressaceae• The family comparises evergreen much branched trees

or shrubs.• The plant parts are arranged opposite decussate or in

whorls of 3 or 4.

• Juvenile leaves may be linear adenate or adpressed

completely hiding the stem.

• Leaves may be glandular and grooved.

• Male and female cones occur on same plant.

• There are nearly 22 genera some are.. Tetraclinis,

Juniperus, Callitris, Thuja etc

THUJA

Podocarpaceae

• Leaves are extreamly variable.

• True leaves are small,scale like and are replaced by phylloclades.

• Phylloclades are flattened much branched with fiabelliform.

• Male and female cones are seprate solitary axile or terminal.

• It consist of 7 genera some are .. Podocarpus, Dacrydium,etc

Podocarpus

macrophyllus

Araucariaceae

• Evergreen and highly resinous trees.

• Leaves are small,stiff,awl-like or large and

leatherhy.

• Plant may be monoecious or dioecious.

• Pollen grain are wingless with multiple

persistant prothalial cells.

• It consist of 2 genera …Araucaria,

Agathis .

Cephalotaxaceae

• Cephalotaxaceae is a monogenic family with only one

genera Cephalotaxus.

• Named such due to shape of male cone from the greek

word “kephale” means head.

• Male cones are present in globose heads.

• Shrubs or small yew like dioecious plants.

• Male trees posses unbranched shoot.

• Leaves are more or less same size

,falcate,subacute,base round,and whitish beneath.

Taxaceae

• These are much branched evergreen woody shrub or small,rarely large trees.

• The leaves are simple,linear and small and sre spirally arranged.

• The wood is pycnoxylic.

• Plant is dioecious with male strobilus consist of a cone axis.

• The family is represented by 5 living genera…. Amentotaxus, Torreya,Taxus,Psedotaxus,Austrotaxus.

2

Cycadophyta

CYCADOPHYTA

• Rarely branched trunks with soft pithy wood.

• Plants are dioceous in nature with compound leaves.

• Microsporangia (Male gametophyte) grows within the ovule.

• Male gametes are multicilliated and motile.

• Motile sperm released after several months, sometimes after the seed has fallen.

Cycads Appeared

on Earth

250 MYA

• Reached their greatest abundance and diversity during the Jurassic

• Declined sharply during the Cretaceous radiation of the angiosperms.

Cycad Stems

• Columnar

• Little branching

• Not very woody

Certain roots in Cycads grow

toward the soil surface

Corraloid

Roots

A Closer Look at Coralloid Roots

• Grow upward near soil

surface

• Branch to form masses

• Root cortex inhabited by

Cyanobacteria (carry

out nitrogen fixation)

Cycads produce pollen and seeds

in cones

• Cones develop at

apex of stem

All Cycads are Dioecious

• Individual plants

produce either pollen

cones or seed cones

Cycas revoluta

Pollen Cone

Seed Cone

Ginkgophytes – Ginkgo

• Extensive fossil record but…only

1 living species: Ginkgo biloba!

•Highly branched tree withwell developed wood.

•Deciduous, fan-shaped leaves with dichotomous

venation.

•Dioecious: male and female trees-male: “cone” with lateral stalks bearing

microsporangia-female: no cone, axis with 2 ovules

(outer integument layer fleshy)

•motile sperm (ancestral

Ginkgo – Vegetative Characteristics

Ginkgo is Deciduous

Ginkgo Stems

• Extensive branching

• Very woody

Ginkgo Stems

long shoot spur shoot

All Ginkgo trees are Dioecious

• Individual plants produce either pollen “cones” or seed

“cones”

• Produced on spur shoots

C

Ginkgo produces a seed with a

fleshy seed coat

• Seed Coat contains Butyric Acid

• Seed Coat is not edible

Ephedra is a desert shrub

Gnetum is a

tropical vine or

small tree

Welwitschia is a bizarre plant of an

extremely arid environment

Welwitschia

produces only two

adult leaves

Welwitschia forms

a short stem and

deep tap root

Thank You