PLANT KINGDOM

Algae divided into 3 classes :

Chlorophyceae :

• Commonly known as Green algae.
• Main pigment is chlorophyll ‘a’ and ‘b’.
• Unicellular, colonial or filamentous.
• Cell wall has inner layer of cellulose and outer layer of pectose.
• Have pyrenoid as the storage body for starch and proteins.

                        e.g., Chlamydomonas, Volvox, Spirogyra.

Phaeophyceae :

• Commonly known as Brown algae and mainly found in marine habitat.
• They possess chlorophyll a, c, carotenoid, xanthophylls and fucoxanthin.
• Cell wall has cellulose and lignin or gelatinous coating of algin.
• Has mannitol and laminarin as reserve food material.
• Body divisible into holdfast, stipe and frond.
• Reproduce asexually by biflagellate pear-shaped zoospores.

                        e.g., Ectocarpus, Fucus, Laminaria.

Rhodophyceae :

• Commonly known as red algae.
• Red color is due to predominance of red pigment r-phycoerythrin in their body along with chlorophyll a, d.
• Found on surface as well as great depths in oceans.
• Cell wall made of cellulose, pectin and polysulphate esters.
• Reserve food material is floridean starch similar to amylopectin and glycogen in structure.
• Reproduce asexually by non motile spores and sexually by non motile gametes (Oogamous type)

                        e.g., Polysiphonia, Porphyra, Gelidium.

BRYOPHYTES : Amphibians of plant kingdom

• Occur in damp, humid places.
• Lack true roots, stem or leaves.
• Plant body attached to the soil by unicellular or multicellular rhizoids.
• Main plant body is haploid (n), or gametophytic.

REPRODUCTION IN BRYOPHYTES :

• Vegetative reproduction by fragmentation.
• Asexual reproduction by gemmae formed in gemma cups.

Sexual reproduction :

• Main plant body is gametophyte.
• The sex organs in bryophytes are multicellular.
• Male sex organ is called antheridium which produces biflagellate antherozoids as male gamete.
• Female sex organ is archegonium is flask shaped and produces a single egg.
• Fertilization takes place in water results in formation of zygote.
• The zygote developed into a multicellular body called sporophyte which remains parasitic on female gametophyte.
• The sporophyte differentiated into foot, seta and capsule.
• Some cells of the capsule undergo meiotic division to produce haploid spores. These spores germinated into an independent gametophyte.
• Moss gametophyte consists of two stages
• First stage is called protonema stage which developed from the spore and is creeping, green, branched.
• Second stage is leafy stage which developed from the protonema stage as a lateral bud. They consist of upright, slender axes bearing spirally arranged leaves.

 

CBSE Biology (Chapter Wise) Class XI ( By Mr. Hare Krushna Giri ) 
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