KINGDOM PLANTAE
· Kingdom-Plantae includes all those organisms that are unicellular or multicellular, eukaryotic, phototrophic and have cellulosic cell wall.
· Kingdom- plantae is divided into two subkingdoms, i.e. Cryptogamae (having conspicious reproductive structures) and Phanerogamae (having visible reproductive structures). Cryptogamae includes algal, bryophytes and pteridophytes and Phanerogamae includes gymnosperms and angiosperms.
· Algae includes all chloropyllous, photosynthetic, thalloid (no differentiation into roots, stems and leaves) plants. These are mostly aquatic plants.
· These plants can reproduce vegetatively by fragmentation, asexually by means of zoospores (flagellated, motile), aplanospores, hypnospores, etc. and sexually by isogamy (fusion between gametes of similar size), anisogamy (fusion between gametes that are dissimilar in size) and oogamy (fusion between large non-motile female gamete and small, motile male gamete)
· Based on the presence of different pigments algae can be divided into Chlorophyceae, Phaeophyceae and Rhodophyceae.
· Chlorophyceae (green algae) these are green due to the presence of chlorophyll-a and b pigments localised in chloroplast and have starch as reserved food material, e.g. Spirogyra, Ulothrix, Volvox, etc.
· Spirogyra is an algae belonging to Chlorophyceae (green algae). It consists of slender unbranched filaments with cells having a number of ribbon-shaped chloroplast and large central vacuole. It reproduces by means of conjugation, which can be lateral (involving two cells of same filament) or scalariform (involving cells of two filaments)
· Ulothrix is also an algae of Chlorophyceae that consists of unbranched filamentous with cells having gridle-shaped chloroplast. It mainly reproduce sexually by isogamy.
· Phaeophyceae (Brown algae) these appear brown in colour due to the presence of pigments chlorophyll-a, c, carotenoids and fucoxanthin. Their plant body is differentiated into holdfast stipe and frond. Their reserved food material Is laminarin and mannitol, e.g. Sargassum, Fucus, Ectocarpus, etc.
· Rhodophyceae (red algae) these appear red in colour due to presence of red pigment phycoerythrin. Their reserve food material is floridean starch, e.g. Polysiphoria, Gelidium, etc. Members of red algae yield carrageenan which is commercially used.
· Bryophytes are the terrestrial plants, which require moisture or water for fertilisation. These are non-vascular, non-seeded plants in which gametophyte dominates the life cycle and sporophyte is dependent upon the gametophyte.
· Embryo formation is seen in them. They can reproduce vegetatively and sexually. Sexual reproduction is strictly oogamous. The female sex organ in them is archegonia while that male sex organ is antheridia. Bryophytes are of two types, i.e. liverworts and mosses.
· Funaria is a moss with leafy plant body that remain attached to the substratum by rhizoids (root like structures). The sex organs are jacketed, multicellular and stalked. Antheridia bears antherozoids and archegonia bear egg cell. Their fusion requires presence of water. After fusion, zygote form embryo that develops into sporophyte which meiotically divide to form spores that germinate into protonema which develop into gametophyte.
· Riccia Is the simplest thalloid bryophyte, i.e. a liverwort. It bears two types of rhizoids smooth walled and tuberculated. Vegetative reproduction through fragmentation. Sexual reproduction is oogamous type via antheridia (male) and archegonia (female). The sporophyte is simple and bears a globular capsule only.
· Pteridophytes are non-seeded plants having vascular tissues. These are dependent on water for fertilisation. Their main plant body is sporophyte, which is well differentiated into roots, stem and leaves. The gametophyte is reduced some of these show advances towards seed habit.
· Dryopteris is commonly called as fern. Its main plant body is sporophytic (2n). The stem is underground (rhizome) and shoot system is well-developed. The leaves show characteristic circinate vernation (young leaves are folded).
· Sporophytes bear sporophylls that are leaf-like appendages with sporangia. Sporangia produces haploid spores that germinate into gametophyte.
· Prothallus is a transitory stage. The gametophyte possess antheridia and archegonia. The male gametes swim in water to reach archegonia. After fusion zygote is formed that develop into sporophyte.
· Asexual reproduction is through spores produced in sporangia, which develop on the ventral surface of leaves. Male and female gametes are produces on gametophyte in special structures called antheridia and archegonia.
· Selaginella is also known as little club moss or spike moss. Its main plant body is sporophytic (2n). It bears microsporophylls (produce microscope) and megasporophylls (produce megaspore) by reduction division in microspore mother cell and megaspore mother cell, respectively. These spores produce male and female gametophytes (n) independently. These bear antheridia and archegonia. Fertilisation occurs through water moisture.
· Gymnosperms are naked-seeded plants that possess exposed ovules on megasporophylls. These plants do not contain their sex organs in flowers.
· Sporophytic plant body dominates the life while the gametophyte is of reduced type.
· These are vascular plants. The plants are heterosporous, i.e. producing microspores (male gametophyte) and megaspore (female gametophyte).
· The male gametes released from microsporangia are carried by pollen tube towards archegonia male gamete fuse with egg to give rise to zygote that develops into embryo which form naked seeds. This group includes some of the largest plants on the earth.
· Cycas is an evergreen woody plant bearing crown of leaves at the top. It bears normal roots and coralloid roots. The male and female cone develop on separate plants. These bears microspore and megaspores. The microspores shed at 3cell stage. Gametes of Cycas are large and motile (unlike all other gymnosperms). The haploid endosperm is formed before fertilisation. After fusion, an embryo is formed and naked seeds are produced. The ovule is anatropus and consists a single integument.
· Angiosperms are the most advanced plants that dominate the entire land. These are found in almost all habitats. These bear flowers as their reproductive structures.
· Gametophytes are reduced and dependent upon the sporophytes. The ovules are retained in the megasporangium. Double fertilisation occurs and it results into the formation of embryo and endosperm (3n).
· George Bentham and Joseph Dalton Hooker presented the system of classification of angiosperms published in Genera Plantarum (1862- 1863), which appeared in three volumes. According to this angiosperm’s are divided into Monocotyledonae and Dicotyledoane.
