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๐Ÿ“– Summaries โ€บ Botany

Plant Kingdom

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Plant Kingdom - Quick Revision

Plantae includes Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms (cyanobacteria/blue-green algae are NO longer 'algae').

Algae

  • Chlorophyll-bearing, simple, thalloid, autotrophic, largely aquatic. Fix about half of Earth's CO2.
  • Sexual reproduction: isogamy (gametes alike, e.g., Ulothrix, Spirogyra), anisogamy (unequal, Eudorina), oogamy (large non-motile egg + small motile sperm, Volvox, Fucus).
  • Three classes (pigment / stored food / examples):
- Chlorophyceae (green): chl a+b, starch, pyrenoids; Chlamydomonas, Volvox, Ulothrix, Spirogyra, Chara. - Phaeophyceae (brown): chl a+c + fucoxanthin, laminarin/mannitol; body = holdfast + stipe + frond; Ectocarpus, Laminaria, Sargassum, Fucus, Dictyota. - Rhodophyceae (red): chl a+d + r-phycoerythrin, floridean starch; Polysiphonia, Porphyra, Gracilaria, Gelidium.
  • Products: agar (Gelidium, Gracilaria), algin (brown), carrageen (red); Chlorella food supplement.

Bryophytes (amphibians of plant kingdom)

  • Live in soil but need water for fertilisation. Main body = HAPLOID gametophyte; rhizoids; no true root/stem/leaf.
  • Antheridium (biflagellate antherozoids) + flask-shaped archegonium (one egg). Sporophyte attached to and dependent on gametophyte; meiosis in sporophyte -> haploid spores.
  • Liverworts (Marchantia): thalloid, dorsiventral; gemmae in gemma cups.
  • Mosses (Funaria, Polytrichum, Sphagnum): protonema stage then leafy stage; sporophyte more elaborate than liverworts. Sphagnum = peat.

Pteridophytes (ferns, horsetails)

  • First terrestrial plants with vascular tissue (xylem + phloem). DOMINANT phase = sporophyte (true root, stem, leaf); gametophyte = free-living prothallus.
  • Sporophylls bear sporangia; meiosis -> spores. Homosporous (one kind) vs heterosporous (Selaginella, Salvinia) = precursor to seed habit.
  • Classes: Psilopsida (Psilotum), Lycopsida (Selaginella, Lycopodium), Sphenopsida (Equisetum), Pteropsida (Dryopteris, Pteris, Adiantum).

Gymnosperms (naked seeds)

  • Ovules not enclosed by ovary wall; seeds naked. Heterosporous. Coralloid roots (Cycas) fix N2; mycorrhiza (Pinus). Sequoia = tallest.
  • Male strobili (microsporophyll+microsporangia) -> pollen grain (reduced male gametophyte); female strobili (megasporophyll+ovules) -> female gametophyte with archegonia. Gametophytes NOT free-living. Pollen tube delivers male gametes; zygote -> embryo, ovule -> naked seed.

Angiosperms (flowering plants)

  • Pollen & ovules in flowers; seeds enclosed in fruits. Smallest Wolffia to tall Eucalyptus. Two classes: dicotyledons and monocotyledons.

Alternation of generations

Gametophyte (n) <-gametes-fertilisation-> sporophyte (2n) <-meiosis-> spores (n). Gametophyte dominant in bryophytes; sporophyte dominant in pteridophytes, gymnosperms, angiosperms.