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BOWEN UNIVERSITY, IWO

PURE AND APPLIED BIOLOGY PROGRAMME

COURSE CODE: BLY 102

COURSE TITLE: GENERAL BIOLOGY II

SEMESTER: SECOND

TITLE: GENERAL CHARACTERISTICS AND STRUCTURE OF PLANT DIVISION

1. Division: Thallophyta

These are plants that do not have well-differentiated body form (i.e. thalloid). They are found both

in terrestrial and aquatic habitats, but are predominantly aquatic; freshwater or marine. It has only

one subdivision Algae. Examples are Spirogyra, Ulothrix, Cladophora and Chara. Various types

of fungi like yeasts and moulds which do not have chlorophyll are also included in this group.

Sub-division: Algae

• They are autotrophs

• The body is simple and not well differentiated (i.e. they possess thalloid body form)

• The form and size of algae are variable. Chlamydomonas is microscopic unicellular algae.

Volvox is in colonial form. Ulothrix and Spirogyra are filamentous.

• They are further classified as green algae, red algae and brown algae. Red and brown algae are due

to the presence of accessory photosynthetic pigments.

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Clamydomonas

Volvox Spirogyra

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2. Division: Bryophyta

The plant body in this group is commonly differentiated to form stem and leaf-like structures.

Roots are not presents, but a small root-like structure called rhizoid is present. They are called the

amphibians of the plant kingdom because they grow in moist areas. It has embryo stage in its

developmental process. The sex organs are multicellular. Male sex organ is called antheridium and

produces antherozoids. Female sex organ is called archegonium and produces a single egg.

Examples are Moss (Funaria) and Marchantia (Liverwort), Anthoceros, Riccia

Diagram of a Moss Showing the sporophyte and gametophyte

A Moss Plant

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Liverwort Riccia

3. Division: Pteridophyta

In this group, the plant body is sporophyte and can be differentiated into roots, stem and leaves. It

is the highest group of cryptogams. They have a specialized tissue for the conduction of water and

other substances form one part of the plant body to another. Hence they are also called vascular

cryptogams. Seeds are absent and they produce naked embryo called spores.

Sporophytes bear sporangia which produce spores. On germination, this spore gives rise to

gametophyte called prothallus. Prothallus bear male sex organ antheridia and female sex organ

archegonia. Some examples are Marsilea, Ferns, Selaginella, Equisetum, Pteris, Adiatum,

Lycopodium and Horsetails.

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Selaginella kraussiana

Selaginella kraussiana Fern (Maiden hair)

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4. Division: Spermatophyta

This is a division of seed producing plants. The seed contain embryo that contains reserve food

(i.e. cotyledon) for future growth. Its main plant body is sporophyte and can be differentiated into

stem, leaves and roots. Male and female gametophytes are distinct. They have a well-developed

vascular system throughout the body. Spermatophyta has two sub-divisions – Gymnospermae and

Angiospermae.

Sub-division: Gymnospermae (Greek; gymno – naked, spermae – seed)

• The plants of this group bear naked seeds and are usually perennial, evergreen and woody.

• It includes medium sized trees and shrubs.

• Sporangia are formed over modified leaf-like structure called sporophylls.

There are two types of sporophylls. Megasporophyll which bears megasporangium (ovules). It

produces female gamete. Microsporophyll which bears microsporangium (pollen sac). It produces

male gamete.

• Examples are Pinus (pines), Cedrus (deodar), Cycas, Picea (Christmas Tree), Thuja (Morpankhi).

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Picea abies Picea abies tree

Sub-division: Angiospermae (Greek – angio – covered, sperma – seed)

These are flowering plants.

• The seeds develop inside an organ which is modified to become a fruit.

• These are the highly evolved group of plants

• The reproductive organs are aggregated into flower. The male sex organs are called stamens and

female sex organs are called pistil.

• Plant embryos in seeds have structures called cotyledons are also called ‘seed leaves’ because in

many instances they emerge and become green when the seed germinates. Cotyledons store food

for developing embryo.

• The angiosperms are divided into two groups on the basis of the number of cotyledons present in

the seed. Plants with seeds having a single cotyledon are called monocotyledonous or monocots

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(e.g. Maize, rice, wheat). Plants with seeds having two cotyledons are called dicots (e.g. garden

pea).

Talinum traingulare an herb Citrus spp. a tree