Notes-Class 9-Science-Chapter-6-Classification of Plants-Maharashtra Board

Topics to be learn :

Kingdom Plantae
Sub-kingdom – Gymnosperms
Sub-kingdom – Angiosperms

Introduction: Classification is the process of categorizing things on the basis of properties. Organisms are grouped together when they have common features.

Living organisms have been classified on the basis of their characteristics, their mode of reproduction, habitat and other structural details.

Robert Whittaker (1959) proposed five kingdom system of classification for the study of living organisms. According to Whittaker the five kingdoms are Monera, Protista, Fungi, Plantae and Animalia.

Botanist named Eichler in 1883 classified the kingdom Plantae into two sub-kingdoms viz. Cryptogams and Phanerogams.

Basis for classiﬁcation of Plants :

Presence or absence of organs.
Presence or absence of separate conducting tissues for the conduction of food and water.
Presence or absence of seeds in plants.
Whether seeds are enclosed in fruits or not.
Number of cotyledons in seeds : one or two.

Criteria used for the classification of plants :

Criteria used for the classification of plants :

There are two subkingdoms of ﬂowering plants, viz., gymnosperms and angiosperms.
If plants do not bear ﬂowers, fruits and seeds, they are non-seed-bearing plants. Contrary to this, if they bear ﬂowers, fruits and seeds, they are seed-bearing plants.
Plants that are not differentiated into organs like roots, stem, leaves are called Thallophyta.
Plants such as pteridophytes, gyinnosperms and angiosperms which possess conducting tissues are included under vascular plants, while bryophytes and thallophytes which do not possess vascular tissues are included under non-vascular plants.
Plants are classified into two groups, viz, seed-bearing and non-seed-bearing plants depending upon the presence or absence of seeds.
Depending upon whether the seeds are enclosed in fruits or not, plants have been classiﬁed as gymnosperms and angiosperms.
Depending upon the number of cotyledons in seeds, plants have been classified into dicotyledons and monocotyledons.

[collapse]

Sub-kingdom : Cryptogams

Plants belonging to sub-kingdom Cryptogams reproduce with the help of spores.

Division I - Thallophyta :

Plants belonging to Division Thallophyta grow mainly in water. Some grow in fresh water, while others grow in marine water.
These plants do not have speciﬁc parts like root, stem, leaves and ﬂowers.
They are autotrophic owing to the presence of chlorophyll. Such plants are called algae (singular alga).
Algae show great diversity. They are either unicellular or multicellular. Some are microscopic while others are macroscopic (large).

Examples : Spirogyra, Ulothrix, Ulva, Chara, Sargassum, etc.

Different types of Fungi, such as yeasts and moulds which do not possess chlorophyll have also been (as per old method of classiﬁcation) included in this group.

Chloroplasts are the special cell organelles found in plants (They are not found in animal cells) that differentiate plant cells from animal cells. Owing to the presence of chloroplasts plants carry out the process of photosynthesis

Spirogyra :

Spirogyra : Spirogyra is a green filamentous alga belonging to the division Thallophyta.

It grows in fresh water.
Owing to the presence of chlorophyll, it synthesises its food by the process of photosynthesis.
It contains spirally arranged thread like chloroplasts in its cells.
In each chloroplast, there are a number of rounded bodies surrounded by starch. These rounded bodies are called pyrenoids.

[collapse]

Division II - Bryophyta :

Plants belonging to the division Bryophyta are called amphibious plants as they grow in moist soil, but need water for reproduction, thus sharing two habitats.
Plants are mostly thalloid (Exception -Mosses), multicellular and autotrophic.
The plant body of bryophytes is ﬂat and ribbon like without true roots. Instead of roots they possess rhizoids.
They do not possess conducting tissues for the conduction of food and water.
Examples : Funaria (moss), Riccia, Marchantia, Anthoceros, etc.

Marchantia :

Marchantia :

Marchantia is a bryophyte.
Marchantia is called amphibious plant, as it shares two habitats, viz, soil for its growth and water for reproduction.
It is ﬂat ribbon-like long and without true roots, stem and leaves.
Instead of roots, it bears rhizoids.
It lacks conducting tissues which conduct food and water.

[collapse]

Division III - Pteridophyta :

Plants belonging to Pteridophyta bears well developed roots, stem and leaves but do not bear ﬂowers and fruits.
They bear separate tissues for the conduction of food and water.
Pteridophytes reproduce by means of spores which are formed on the posterior side of their leaves.
Reproduction in Pteridophytes occur asexually by spores and sexually by zygote formation.
Examples : Nephrolepis, Adiantum, Pteris, Marsilea, Selaginella, Equisetum, Lycopodium, etc.

Ornamental plants :

Ornamental plants : Ornamental plants like fern seen in gardens.

They are called ornamentals as they beautify the place wherever they grow.
Since they are grown in gardens they do not bear flowers and fruits, but they bear different types attractive leaves.
They reproduce by Spores which develop on the lower side of their leaﬂets in the form of sori (singular — sorus).

[collapse]

Sub-kingdom — Phanerogams :

Phanerogams are characterised by the presence of ﬂowers, fruits and seeds.
Phanerogams are further classified into gymnosperms and angiosperms.
In gymnosperms the seeds are naked while in angiosperms the seeds are enclosed in fruits.

Gymnosperms and Angiosperms :

(1) Division I – Gymnosperms : Gymnos - naked, sperms — seeds

Gymnosperms are perennial, woody and evergreen plants.
The stems of gymnosperms are unbranched.
The leaves form a crown at the top of the plant.
They bear male and female ﬂowers on different sporophylls of the same plant.
Seeds are not enclosed in fruits.
Examples Cycas, Thuja, Picea, Pinus, etc.

(2) Division II — Angiosperms : Angios - concealed or hidden, Sperms - seeds

Angiosperms are those plants in which the seeds are concealed.
These plants possess all organs such as roots stem, leaves.
Flowers are reproductive organs of these plants.
Angiosperms are divided into two groups, viz. monocots and dicots depending on the number of cotyledons in their seeds.

[collapse]

Difference between Monocot and Dicot : :

Difference between Monocot and Dicot :

Monocot

Dicot

1-Fibrous root.

2-Stem unbranched.

3-Leaves show parallel venation.

4-Flowers with 3 partsor in their multiples. (Trimerous)

5-Examples : Maize, banana, wheat, jowar

1-Tap root.

2-Stem branched.

3-Leaves show reticulate venation.

4-Flowers with 4 or 5 parts or in their multiples. (Tetra orpentamerous)

5-Examples : Sunﬂower, mustard beans.

[collapse]

1-Hibiscus (A dicot plant) :

(1) Hibiscus (A dicot plant) :

Root : Tap root

Stem : Erect and branched

Leaf : Simple, alternate, with reticulate, venation

Flower : Pedicillate, complete, bisexual

Calyx : Sepals-5, Gamosepalous

Corolla : Petals-5, Gamopetalous

Androecium : Stamen indeﬁnite. Filaments are united to form a staminal tube. The staminal tube bears reniform (kidney shaped) anthers.

Gynooclum : Pentacarpellary, syncarpous

[collapse]

2-Onion (Alliurn cepa) (A monocot plant) :

(2) Onion (Alliurn cepa) (A monocot plant): A small herb with tunicated bulb

Root : Fibrous

Stem : Underground stem (bulb)

Leaves : Hollow and tubular

Flower : Complete, bisexual

Perianth : Made up of 6 lobes, arranged in two whorls of 3 each.

Androecium : Made up of 6 stamens, Epiphyllous

Gynoecium : Tricarpellary, syncarpous, ovary sperior

[collapse]

Maize :

Maize (Monocotyledonous plant) : The seed of maize has single cotyledon. The plant has fibrous roots and hollow, false stem. The leaves show parallel venation. Flowers are with trimerous symmetry. Therefore, maize is called monocotyledonous plant.

[collapse]

PDF-Notes,Solution,Text Book