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Plant kingdom
- 2. CLASSIFICATION OF PLANT KINGDOM ALGAE BRYOPHYTES PTERIDOPHYTES GYMNOSPERMS ANGIOSPERMS
- 3. ALGAE • Chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic organisms • Size ranges from the microscopic unicellular forms (Chlamydomonas) to colonial forms (Volvox) and to the filamentous forms (Ulothrix and Spirogyra) • The algae reproduce by vegetative, asexual and sexual methods • Vegetative reproduction is by fragmentation • Asexual reproduction is by the production of different types of spores (zoospores) • Sexual reproduction takes place through fusion of two gametes
- 4. Classification of algae Chlorophyceae Phaeophyceae Rhodophyceae
- 5. Chlorophyceae • commonly called green algae • chlorophyll a and b. • most of the members have one or more storage bodies called pyrenoids located in the chloroplasts • algae store food in the form of oil droplets • Vegetative reproduction usually takes place by fragmentation • asexual reproduction is by flagellated zoospores produced in zoosporangia • sexual reproduction shows considerable variation in the type and formation of sex cells and it may be isogamous, anisogamous or oogamous • Chlamydomonas, Volvox, Ulothrix, Spirogyra and Chara
- 7. Phaeophyceae • Commonly known as brown algae • chlorophyll a, c, carotenoids and xanthophylls • Food is stored as complex carbohydrates, which may be in the form of laminarin or mannitol • Vegetative reproduction takes place by fragmentation. • Asexual reproduction by biflagellate zoospores that are pear-shaped and have two unequal laterally attached flagella • Sexual reproduction may be isogamous, anisogamous or oogamous. • Ectocarpus, Dictyota, Laminaria, Sargassum and Fucus
- 9. Rhodophyceae • Commonly known as red algae • red pigment, r-phycoerythrin • The food is stored as floridean starch which is very similar to amylopectin and glycogen in structure. • The red algae usually reproduce vegetatively by fragmentation • They reproduce asexually by non-motile spores • Sexual reproduction is oogamous and accompanied by complex post fertilisation developments • Polysiphonia, Porphyra, Gracilaria and Gelidium
- 11. BRYOPHYTES • Amphibians of the plant kingdom • Can live in soil but are dependent on water for sexual reproduction • It is thallus-like and prostrate or erect, and attached to the substratum by unicellular or multicellular rhizoids • They lack true roots, stem or leaves • It produces gametes, hence is called a gametophyte
- 12. • The male sex organ is called antheridium • They produce biflagellate antherozoids • The female sex organ called archegonium is flask- shaped and produces a single egg • The antherozoids are released into water where they come in contact with archegonium • Zygotes produce a multicellular body called a sporophyte • Some cells of the sporophyte undergo reduction division (meiosis) to produce haploid spores. • These spores germinate to produce gametophyte
- 14. Liverworts • Grow usually in moist, shady habitats such as banks of streams, marshy ground, damp soil, bark of trees and deep in the woods • The plant body of a liverwort is thalloid • Asexual reproduction in liverworts takes place by fragmentation of thalli, or by the formation of specialised structures called gemmae • The gemmae become detached from the parent body and germinate to form new individuals • During sexual reproduction, sporophyte is differentiated into a foot, seta and capsule. • After meiosis, spores are produced within the capsule. • These spores germinate to form free-living gametophytes • Marchantia
- 16. Mosses • Protonema stage, develops directly from a spore, is a creeping, green, branched and frequently filamentous stage • Leafy stage, develops from the secondary protonema as a lateral bud, consist of upright, slender axes bearing spirally arranged leaves • This stage bears the sex organs • Vegetative reproduction in mosses is by fragmentation and budding in the secondary protonema • The sex organs antheridia and archegonia are produced at the apex of the leafy shoots. • Zygote develops into a sporophyte, consisting of a foot, seta and capsule • Spores are formed after meiosis • Funaria, Polytrichum and Sphagnum
- 17. Sphagnum Funaria
- 18. PTERIDOPHYTES • Main plant body is a sporophyte which is differentiated into true root, stem and leaves • Possess well-differentiated vascular tissues • The sporophytes bear sporangia that are subtended by leaf-like appendages called sporophylls • Sporophylls may form distinct compact structures called strobili or cones • The sporangia produce spores by meiosis in spore mother cells • The spores germinate to give rise to gametophytes called prothallus
- 19. • Gametophytes bear male and female sex organs called antheridia and archegonia • Fusion of male gamete with the egg present in the archegonium result in the formation of zygote • Zygote thereafter produces a multicellular well- differentiated sporophyte which is the dominant phase of the pteridophytes • The megaspores and microspores germinate and give rise to female and male gametophytes • Psilotum, Selaginella, Lycopodium,Equisetum, Dryopteris, Pteris, Adiantum
- 20. Equisetum
- 21. GYMNOSPERMS • Gymnosperms include medium-sized trees or tall trees and shrubs • The roots are generally tap roots. Roots in some genera have fungal association in the form of mycorrhiza (Pinus) • in some others (Cycas) small specialised roots called coralloid roots are associated with Nitrogen fixing cyanobacteria • The stems are unbranched (Cycas) or branched (Pinus, Cedrus) • The leaves may be simple or compound • The gymnosperms are heterosporous; they produce haploid microspores and megaspores.
- 22. cycas pinus
- 23. • The male or female cones or strobili may be borne on the same tree (Pinus) or on different trees (Cycas). • The strobili bearing microsporophylls and microsporangia are called microsporangiate or male strobili. • The cones bearing megasporophylls with ovules or megasporangia are called macrosporangiate or female strobili • The pollen grain is released from the microsporangium. They are carried in air currents and come in contact with the opening of the ovules borne on megasporophylls • Following fertilisation, zygote develops into an embryo and the ovules into seeds. These seeds are not covered.
- 25. ANGIOSPERMS • The pollen grains and ovules are developed in specialised structures called flowers. • The seeds are enclosed by fruits • They are divided into two classes : the dicotyledons and the monocotyledons • The dicotyledons are characterised by having two cotyledons in their seeds while the monocolyledons have only one
- 26. • The male sex organs in a flower is the stamen • Stamen consists of a slender filament with an anther at the tip • Anthers, following meiosis, produce pollen grains.
- 27. The female sex organs in a flower is the pistil or the carpel Pistil consists of an ovary enclosing one to many ovules • Within ovules are present highly reduced female gametophytes termed embryosacs • Each embryo-sac has a three-celled egg apparatus – one egg cell and two synergids, three antipodal cells and two polar nuclei
- 28. • Pollen grain, after dispersal from the anthers, are carried by wind or various other agencies to the stigma of a pistil • This is called pollination • One of the male gametes fuses with the egg cell to form a zygote • The other male gamete fuses with the diploid secondary nucleus to produce the triploid primary endosperm nucleus • This event is termed as double fertilisation • Ovules develop into seeds and the ovaries develop into fruit