Plant Kingdom (3
NCERT
Motes
8.0 Introduction
Plant Kingdom comprises of multicellular, photosynthetic
organisms constituting the predominant
HDproducers of the biosphere. They may be
aquatic, terrestrial or may even occupy other habitats. They
comprise of hundreds to thousands of different species. Owing to this vast
diversity and number of
species, various classification systems have been formulated from time to time. For
example, Linnaeus
(1754) divided Plant Kingdom into 25 classes on basis of number of stamens and
union and their presence or absence in a carpels, their
flower, etc. Linnaeus' system was wholly artificial, based
on sexual characters of
plants.
Artificial systems separated the closely related
species since they were based on a few characteristics.
Also, the artificial systems gave equal weightage to vegetative
and sexual characteristics; this is
not acceptable since we know that often the vegetative characters are more easily affected by
environment. As against this, natural classification systems were based on natural affinities
among the organisms and consider, not only the external features, but also internal features, like
ultrastructure, anatomy, embryology and phytochemistry. Such a classification for
flowering plants
was given by George Bentham and Joseph Dalton Hooker
At present phylogenetic classification systems based on evolutionary relationships between the
various organisms are acceptable. This assumes that organisms belonging to the same taxa have a
common ancestor
Plant kingdom is classified based on phylogeny and inter-relationships into Cryptogamae and
Phanerogamae.
Numerical taxonomy is now easily carried out using computers and is based on all
observable characteristics. Number and codes are assigned to all the characters and the
data are then processed. In this way each character is
given equal importance and at the
same time hundreds of characters
be considered
can
Cytotaxonomy is based on cytological intormation like chromosome number, structure,
behaviour.
Chemotaxonomy uses the chemical constituents of the plant to resolve confusions and
are also used by taxonomists these days.
, at your Fingertips
wutG Objective NCERT
42
8.1 Algae
organisms. They
General Characteristics
fresh water and marine)
autotrophic and largely aquatic (both also occur in symbiotic
Algae chlorophyllous, simple thalloid, moist stones, soils and wood. Some algae
are
terrestrial habitats
like occur in association
of other Some algae may also
also occur in a variety association of algae with fungi.
a s o c i a t i o n Lichen is good
example of symbiotic
with animals (e.g., on sloth bear).
Algae of unusual habitats are as follows: concentration of salts,
and salt lakes and can withstand high
Occur in saline sea water
alophytic algae
e.g.. Chlamydomonas ehrenbergi, Stephnoptera. and Microspora are
and angiosperms, e.., Oedogonium
tpiphytic algae Grow on larger algae, bryophytes
found attached to larger species of Vaucheria, Cladophora
and Rhizoclonium.
Grow on animals such as snails, fishes and tortoise, e.g., Cladophora
crispata (epizoic on snail
tpizoic algae
shell)
within the bodies of various freshwater
tndozoic algae Occur in tissues of animals, e.g., Zoochlorella occur
protozoans and invertebrates.
Parasitic algae Grow as parasites on many plants and animals, e.g., Cephaleuros virescens causes red rust
in tea and coffee plantations.
Thermophytes Occur in hot water springs (50-70°C temperature) as are able to survive high temperatures
due to absence of wel organised nucleus, e.g., Oscillatoria brevis.
The form and size of algae is highly variable. Algae shows microscopic, unicellular forms like Chlamydomonas. Chlorella
and Spirulina are non-motile and Clamydomonas is motile. Some algae also show colonial forms like Volvox while some
algae show filamentous forms like Ulothrix and Spirogyra. Some brown algae are very large. They are called trees of seas
or kelps These marine forms massive plant bodies.
Thevegetative structure of algae is called thallus. The algal cell wall consists of two layers- () Inner layer made up of
cellulose and (i) Outer layer made up of pectin.
The algae consist of
various types of photosynthetic pigments. Chlorophyll a is present in all groups of algae. The accessory
pigments present in algae are chlorophyll b, chlorophyll c and d, carotenes, xanthophylls and phycobilins. Carotenoids
are of types (i) Carotenes Orange coloured (Gi) Xanthophylls -Yellow coloured. Phycobilins are also
two
(6) Phycocyanins (i) Phycoerythrins. The reserve food material in
of two types-
algae is in the form of (i) Starch, (i) Laminarin starch,
(i) Mannitol and (iv) Floridean starch.
The algae reproduce by vegetative, asexual and sexual methods. Vegetative reproduction is by fragmentation. Each
fragment develops intoa thallus. Asexual reproduction is by the production of different types of spores. Zoospores are
the most common asexual spores produced by algae. Zoospores are tlagelated and hence motile. They on germination give
rise to new plants. Sexual reproduction takes place through fusion of two gametes. It may occur by
or oogamy.
isogamy, anisogamy
Sexual Reproduction
Isogamy Anisogamy Oogamy
It both mnaie and female gametes are Fusion of two gametes dissimilar in size is
Here female gamete is large,
rmorphologically and physiologicaily similar, termed as anisogamous.
then it is calied isogamy
non-motile (non-flagellate)
Here one gamete is larger and termed
Here gametes may be flagellated or non
as and food storing. While
macrogamete or female gamete. While male gamete is small, motile
fiagellated another gamete is smaller and termed as (flagellated)and non-food
microgamete or male yanete storing
NCERT
Motes
8.0 Introduction
Plant Kingdom comprises of multicellular, photosynthetic
organisms constituting the predominant
HDproducers of the biosphere. They may be
aquatic, terrestrial or may even occupy other habitats. They
comprise of hundreds to thousands of different species. Owing to this vast
diversity and number of
species, various classification systems have been formulated from time to time. For
example, Linnaeus
(1754) divided Plant Kingdom into 25 classes on basis of number of stamens and
union and their presence or absence in a carpels, their
flower, etc. Linnaeus' system was wholly artificial, based
on sexual characters of
plants.
Artificial systems separated the closely related
species since they were based on a few characteristics.
Also, the artificial systems gave equal weightage to vegetative
and sexual characteristics; this is
not acceptable since we know that often the vegetative characters are more easily affected by
environment. As against this, natural classification systems were based on natural affinities
among the organisms and consider, not only the external features, but also internal features, like
ultrastructure, anatomy, embryology and phytochemistry. Such a classification for
flowering plants
was given by George Bentham and Joseph Dalton Hooker
At present phylogenetic classification systems based on evolutionary relationships between the
various organisms are acceptable. This assumes that organisms belonging to the same taxa have a
common ancestor
Plant kingdom is classified based on phylogeny and inter-relationships into Cryptogamae and
Phanerogamae.
Numerical taxonomy is now easily carried out using computers and is based on all
observable characteristics. Number and codes are assigned to all the characters and the
data are then processed. In this way each character is
given equal importance and at the
same time hundreds of characters
be considered
can
Cytotaxonomy is based on cytological intormation like chromosome number, structure,
behaviour.
Chemotaxonomy uses the chemical constituents of the plant to resolve confusions and
are also used by taxonomists these days.
, at your Fingertips
wutG Objective NCERT
42
8.1 Algae
organisms. They
General Characteristics
fresh water and marine)
autotrophic and largely aquatic (both also occur in symbiotic
Algae chlorophyllous, simple thalloid, moist stones, soils and wood. Some algae
are
terrestrial habitats
like occur in association
of other Some algae may also
also occur in a variety association of algae with fungi.
a s o c i a t i o n Lichen is good
example of symbiotic
with animals (e.g., on sloth bear).
Algae of unusual habitats are as follows: concentration of salts,
and salt lakes and can withstand high
Occur in saline sea water
alophytic algae
e.g.. Chlamydomonas ehrenbergi, Stephnoptera. and Microspora are
and angiosperms, e.., Oedogonium
tpiphytic algae Grow on larger algae, bryophytes
found attached to larger species of Vaucheria, Cladophora
and Rhizoclonium.
Grow on animals such as snails, fishes and tortoise, e.g., Cladophora
crispata (epizoic on snail
tpizoic algae
shell)
within the bodies of various freshwater
tndozoic algae Occur in tissues of animals, e.g., Zoochlorella occur
protozoans and invertebrates.
Parasitic algae Grow as parasites on many plants and animals, e.g., Cephaleuros virescens causes red rust
in tea and coffee plantations.
Thermophytes Occur in hot water springs (50-70°C temperature) as are able to survive high temperatures
due to absence of wel organised nucleus, e.g., Oscillatoria brevis.
The form and size of algae is highly variable. Algae shows microscopic, unicellular forms like Chlamydomonas. Chlorella
and Spirulina are non-motile and Clamydomonas is motile. Some algae also show colonial forms like Volvox while some
algae show filamentous forms like Ulothrix and Spirogyra. Some brown algae are very large. They are called trees of seas
or kelps These marine forms massive plant bodies.
Thevegetative structure of algae is called thallus. The algal cell wall consists of two layers- () Inner layer made up of
cellulose and (i) Outer layer made up of pectin.
The algae consist of
various types of photosynthetic pigments. Chlorophyll a is present in all groups of algae. The accessory
pigments present in algae are chlorophyll b, chlorophyll c and d, carotenes, xanthophylls and phycobilins. Carotenoids
are of types (i) Carotenes Orange coloured (Gi) Xanthophylls -Yellow coloured. Phycobilins are also
two
(6) Phycocyanins (i) Phycoerythrins. The reserve food material in
of two types-
algae is in the form of (i) Starch, (i) Laminarin starch,
(i) Mannitol and (iv) Floridean starch.
The algae reproduce by vegetative, asexual and sexual methods. Vegetative reproduction is by fragmentation. Each
fragment develops intoa thallus. Asexual reproduction is by the production of different types of spores. Zoospores are
the most common asexual spores produced by algae. Zoospores are tlagelated and hence motile. They on germination give
rise to new plants. Sexual reproduction takes place through fusion of two gametes. It may occur by
or oogamy.
isogamy, anisogamy
Sexual Reproduction
Isogamy Anisogamy Oogamy
It both mnaie and female gametes are Fusion of two gametes dissimilar in size is
Here female gamete is large,
rmorphologically and physiologicaily similar, termed as anisogamous.
then it is calied isogamy
non-motile (non-flagellate)
Here one gamete is larger and termed
Here gametes may be flagellated or non
as and food storing. While
macrogamete or female gamete. While male gamete is small, motile
fiagellated another gamete is smaller and termed as (flagellated)and non-food
microgamete or male yanete storing
