3. Kingdom Plantae_Cryptogamae

 

3. Kingdom : Plantae

•Can you recall?

1. Why do we call as plants are producers on land ?

2. What are differences between sub-kingdoms Cryptogamae and Phanerogamae?

3. Differentiate between Thallophytes and Bryophytes.

4. Give any two examples of Pteridophyta.

3.1 Kingdom plantae :

•Kingdom Plantae is further classified on the basis of characteristics like

–absence or presence of seeds,

–vascular tissues,

–differentiation of plant body, etc.

•Phanerogams – (Phaneros = visible)

–They are commonly called seed producing plants.

–They produce special reproductive structures that are visible.

•Cryptogams – (kryptos = hidden, gamos = marriage)

–They are spore producing plants and do not produce seeds and flowers.

–They reproduce sexually by gametes but sex organs are concealed.

•Classification of Kingdom Plantae is represented as follows :

•3.2 Salient features of major plant groups under Cryptogams :

•A. Division : Thallophyta –

•Members are mostly aquatic, few grow on other plants as epiphytes.

•Some grow symbiotically and epizoic

•  i.e. growing or living non-parasitically on the exterior of living organisms.

•Aquatic algae grow in marine or fresh water.

•Most of them are free living while some are symbiotic.

•Plant body is thalloid

•  i.e. undifferentiated into root, stem and leaves.

•They may be

•  small, unicellular, microscopic like Chlorella (non-motile),        Chlamydomonas (motile).

•They can be

        • multicellular, unbranched, filamentous like Spirogyra or

        • branched, filamentous like Chara.

•Sargassum, a huge macroscopic sea weed which measures more than 60 meters in length is also an alga.

•The algal cell wall contains either

•  polysaccharides like cellulose / glucose or

•  a verity of proteins or both.

•Reserve food is in the form of starch and its other forms.

•Reproduction takes place by vegetative, asexual and sexual way.

•The life cycle shows phenomenon of alternation of generation,

–dominant haploid and reduced diploid phases.

•Algae are classified as per its pigments like chlorophyll, xanthophylls and phycobilin.

a. Chlorophyceae (green algae) :

•These are mostly fresh water (few brackish water and marine).

•Plant body is unicellular, colonial, filamentous.

•Cell wall contains cellulose.

•Chloroplasts are of various shapes like discoid, plate-like, reticulate, cup-shaped, ribbon-shaped or spiral with chlorophyll a and b.

•The stored food is in the form of starch.

•Pyrenoids are located on Chloroplast.

•Members are rich in protein, so used as food; used even by space travelers.

•    e.g. Chlorella. Chlamydomonas, Spirogyra, Chara, Volvox, Ulothrix

b. Phaeophyceae (Brown algae) :

• Mostly marine, rarely fresh water.

•Simple branched / filamentous (e.g. Ectocarpus) / profusely branched (Petalonia).

•Cell wall has cellulose, fucans and algin.

•Photosynthetic pigments like chlorophyll-a, c and fucoxanthin are present.

•Mannitol, laminarin and starch are stored food materials.

•Body is usually differentiated into holdfast, stalk called stipe and leaf-like photosynthetic

 organ called frond.

•Many species of marine algae are used as food.

•e.g. Laminaria, Sargassum.

•Some species are used for production of  hydrocolloids.

–a substance which forms a gel in presence of water.

•e.g. Ectocarpus, Fucus, etc.

c. Rhodophyceae (Red algae):

• These are found in marine as well as fresh water on the surface, deep sea and brackish water.

•Plant body is thalloid.

•Cells contain chlorophyll a, d and phycoerythrin.

•Cell wall is made up of cellulose and pectin glued with other carbohydrates.

•Stored food is in the form of Floridean starch.

•Commercially important agar-agar which is used as solidifying agent in tissue culture medium is obtained from red algae.

•  e.g. Chondrus, Batrachospermum, Porphyra, Gelidium , Gracillaria,   Polysiphonia, etc.

•Internet my friend

•  1. Economic importance of algae.

•  2. Role of algae in environment.

•  3. Different forms of green, red, brown and blue green algae.

•Do you know ?

•Brown algae- kelps may grow up to 100 meters in height.

•Find out more information about Sargasso sea.

•Can you tell?

•  1. What are the three major groups of Cryptogams ?

•  2. Name the accessory pigments of algae.

•  3. Give salient features of algae.

•      Differentiate between Chlorophyceae and Phaeophyceae.

•  4. Enlist examples of Chlorophyceae and Rhodophyceae.

•Observe and Discuss

•You may have seen Funaria plant in rainy season. Why is it called amphibious plant?

•B. Bryophyta (Bryon : moss ; phyton : plant)

•Bryophytes are mostly terrestrial plants.

•They are found in moist shady places.

•But they need water for fertilization and completion of their life cycle.

–Hence they are called ‘amphibious plants’.

•They include approximately 960 genera and about 25,000 species.

•Life cycle of Bryophytes shows sporophytic and gametophytic stages.

•Vegetative plant body is thalloid or leafy which represents gametophytic generation.

•Spore producing capsule represents sporophytic generation.

•Bryophytes have root-like structures called rhizoids.

•Rhizoids are

–unicellular in liverworts while

–multicellular in mosses.

•Rhizoids

–absorb water and minerals and also

–help in fixation of thallus on the substratum.

•Bryophytes are divided into two groups:

•1. Liverworts and

•2. Mosses

•a. Liverworts (Hepaticeae) :

•These are lower members of Bryophyta.

•These are primitive group of Bryophytes.

•Gametophyte possesses flat plant body called thallus.

•The thallus is green, dorsiventral, and prostrate with unicellular rhizoids.

•e.g. Riccia, Marchantia.

•Hornworts (Anthocerotae) –

–These member possess flattened thallus.

–The thallus produces horny structures which are called sporophytes

•hence the name hornworts.

–e.g. Anthoceros

b. Mosses (Musci) :

•These are advanced members of Bryophyta which possess erect plant body.

•Gametophytic phase of the life cycle includes two stages namely;

–Protonema stage and

–Leafy stage

•Protonema stage –

–It is prostrate, green, branched

–and filamentous

–It is also called juvenile gametophyte.

–It bears many buds.

•Leafy stage –

–It is produced from each bud.

•Thus protonema helps in the vegetative propagation.

–The leafy stage has erect, slender stem like (Cauloid) main axis bearing spiral leaf like structures (Phylloid).

–It is fixed in soil by multicellular branched rhizoids.

–This stage bears sex organs.

–Vegetative reproduction takes place by fragmentation and budding in secondary protonema.

•e.g. Funaria, Polytrichum, Sphagnum , etc.

Economic importance -

•Some mosses provide food for herbivorous mammals, birds, etc.

•Species of Sphagnum, a moss; provides peat used as fuel.

•Mosses are also used as packing material for transport of living materials because they have significant water holding capacity.

•Just like lichens, mosses are the first living beings to grow on rocks.

•They decompose rocks to form soil and make them suitable for growth of higher plants.

•Dense layers of mosses help in prevention of soil erosion, thus act as soil binders.

•

C. Pteridophyta (Pteron = feather, phyton = plant)

•Evolutionarily, Pteridophytes are the first vascular and true land plants.

–Hence considered as the first successful terrestrial plants with true roots, stem and leaves.

•These plants have a primitive conducting system.

•They are the only Cryptogams with vascular tissues.

•Pteridophytes grow in moist and shady places.

•The group has about 400 genera and 11,000 species.

•The plants consist of pinnate (feather like) leaves.

•The late Paleozoic era is regarded as the age of Pteridophytes

•Leaves may be

–small called microphylls e.g. Selaginella

or

–large called macrophylls e.g. Nephrolepis (fern)

•Pteridophytes show sporophytic and gametophytic stages in life cycle.

  e.g. Ferns, Horsetail.

•Some are aquatic

–e.g. Azolla, Marsilea,

•Xerophytic

–e.g. Equisetum and

•Epiphytic 

–e.g. Lycopodium

•Pteridophytes show heteromorphic alternation of generations.

•The sporophyte is diploid, dominant, autotrophic and independent.

•It is differentiated into root, stem and leaves.

•The primary root is short lived and soon replaced by adventitious roots.

•The stem may be aerial or underground.

•Leaves may be

–scaly (Equisetum)

–simple and sessile (Lycopodium) or

–large and pinnately compound (Nephrolepis / Ferns).

•In these members

–Xylem consists of only tracheids and

–Phloem consists of only sieve cells

•Secondary growth is not seen in Pteridophytes due to absence of cambium.

•Pteridophytes are classified as -

–Psilopsida- (Psilotum),

–Lycopsida - (Selaginella and Lycopodium),

–Sphenopsida - (Equiesetum) and

–Pteropsida - (Dryopteris, Pteris and Adiantum)

•Economic importance –

•Pteridophytes are Used for medicinal purpose .

•They are also good soil binders.

•Many varieties are grown as ornamental plants.

-- Deshmukh A. B.