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Characteristics of Kingdom Plantae
- 1. Multicellular
- 2. Photosynthetic (chloroplasts)
- 3. Cellulose in cell walls
- 4. Starch as a storage polysacharide
- 5. Alternation of generations
- 6. Heterogamy with gametes produced in gametangia
Nonvascular Plants studied in lab
- Phylum Bryophyta - mosses
- Phylum Hepatophyta - liverworts
Vascular Plants studied in lab
- Seedless plants:
- Phylum Lycophyta - club mosses
- Phylum Pterophyta - ferns, horsetails, whisk ferns
Plant Life Cycles
- Alternation of generations: plants alternate between haploid gametophyte generation and a diploid sporophyte generation.
- Diploid sporophyte generation is the dominant generation in all plants except bryophytes.
- 1. The gametophyte produces gametes inside a jacket of cells forming gametangia.
- 2. Eggs are produced by mitosis in archegonia and sperm are produced in antheridia.
- 3. The gametes fuse by entrance of the sperm into the archegonium, forming a diploid zygote, the first stage of the diploid sporophyte generation.
Plant life cycle produces gametes by mitosis; spores are produced by meiosis.
Plants less adapted to land
- No vascular tissue (mass).
- No true roots, stems, leaves.
- Sperm swims to egg so water is required for sexual reproduction.
- Gametophyte generation predominates.
- Sporophyte dependent on gametophyte.
- Homospory, one type of spore (all identical).
- Dispersal by spores.
Plants better adapted to land
- Vascular tissue (xylem, phloem).
- Roots, stem, leaves.
- Water not required for sexual reproduction (sperm nuclei inside pollen grain).
- Sporophyte generation predominates.
- Gametophyte reduced and dependent on sporophyte.
- Heterospory, two kinds of spore (micro [male] and mega [female] spores).
- Dispersal by seeds.
Spore vs Seed
- A haploid (n) cell inside a dessication resistant coat.
- Germinates to give rise to a multicellular haploid plant-gametophyte.
- A diploid sporophyte embryo plus nutritive material inside a dessication resistant seed coat.
- Germinates to give rise to a multicellular mature diploid plant (sporophyte).
Nonvascular Plants (Bryophytes)
- Gametophyte is the dominant generation.
- Restricted to moist habitats for their reproductive cycle.
- Remains close to ground enabling the motile sperm to swim from the antheridium to the archegonium and fertilize egg.
- Have a cuticle but lack stomata on the surface of the gametophyte thallus (plant body).
- Stomata is present on the sporophyte in some.
- Steps of fertilization:
- Sperm swim through a film of water to the archegonium and swim down the neck of the egg.
- The diploid zygote divides by mitosis and develops into an embryonic sporophyte within the archegonium.
- Spores develop by meiosis in the sporangium at the end of the sporophyte. The spores are discharged and in a favolable environment develop into new gametophytes.
- Liverworts have a flat thallus.
- Rhizoids; rootlike extensions on the lower surface, that primarily anchor plants.
- Pores; openings that function in gas exchange.
- Gemmae cups; contain flat disks of green tissue called gemmae.
- Gemmae are washed out of the cups when it rains, and they grow into new, genetically identical liverworts.
Ancestral vs Derived Features of Nonvascular Plants as they relate to Adaptation to Land
- Mobile sperm (require water).
- No vascular tissue.
- No roots, stems, leaves.
- Gametophyte dominant.
- Sporophyte depends on gametophyte.
- Gameotangia and sporangia.
- Stomata on moss.
Seedless Vascular Plants
- All have vascular tissue, which is specialized for conducting water, nutrients, and photosynthetic products.
- Sporophyte is the dominant generation.
- Gametophyte usually independent of sporophyte.
- Have well developed leaves, roots, stomata and structural support tissue.
- Retain ancestral feature of motile sperm that require water for fertilization, the gametophyte is small and restricted to moist habitats.
- Lycophyta (club mosses, spike mosses, quillworts) and Pterophyta (ferns, horsetails, whisk ferns).
Lycophyta: Club mosses
- Usually in moist habitats except Selaginella, the resurrection plant, that inhabits deserts.
- Nonvascular plants and most seedless vascular plants produce one type of spore (homospory).
- Produce two kinds of spores (heterospory), unusual.
- Megaspores; large spores divide by mitosis to produce female gametophyte.
- Microspores; numerous small spores that produce male gametophyte by mitosis.
Pterophyta: ferns, horsetails and whisk ferns
Psilophytes (whisk ferns) are diminutive, dichotomously branched (Y branches), photosynthetic stems that reproduce sexually by aerial spores.
- Sphenophytes (horsetails) have green jointed stems with occasional clusters of leaves or branches. Their cell walls contain silica that give the stem a rough texture.
- Contain strobili which are clusters of sporangia that produce spores.
- Ferns are the most succesfull occupying deserts to tropical rain forests. They have rhizoids to anchor the plant.
- Contain sori which are clusters of sporangia and leaves called sporophylls.
Fern Life Cycle
- The haploid spores of ferns fall to the ground and grow into heart-shaped, gametophyte plants.
- All seedless plants depend on an external source of water for a sperm to swim to an egg to effect fertilization and for growth of the resulting sporophyte plant.
- Eggs cells are produced by mitosis in urnlike structures callend archegonia, and sperm cells are produced by mitosis in globular structures callend artheridia.
Ancestral vs Derived Features of Seedless Vascular Plants as they relate to Adaptation to Land
- Sperm requires water for fertilization.
- Reduce gametophyte but usually independent.
- Vascular Tissue.
- Independent sporophyte.
- Complex stomata.
- Waxy cuticle.
Features of the Success Land Plants
- Gametangium: protects production of gamtes from drying out.
- Cuticle: prevents dessication of plant body.
- Rhizoid: anchors plant to the ground.
- Motile sperm: liability of land because water is needed for reproduction.
- Vascular tissue: transport and support.
- Gemma cups: production of new haploid plants by asexual reproduction.
Major difference between the alternation of generations in life cycles
Nonvascular: gametophyte dominate
Seedless: sporophyte dominate
Structures and Functions
- Antheridium: produce and protect sperm. In gametophyte. Eg. fern, liverwort, mosses.
- Archegonium: produce and protect eggs. In gametophyte. Eg. fern, liverwort, mosses.
- Spore: dispersal. In gametophyte. Eg. fern, liverwort, mosses.
- Gamete: fuse to restore diploid number of chromosomes. In gametophyte. Eg. fern, liverwort, mosses.
- Rhizome: underground stem to anchor the plant. In sporophyte. Only in fern.
- Gemma: asexual reproduction. In gametophyte. Only in liverwort.
- Sporangium: protects spores, site of meiosis. In sporophyte. Eg. moss, fern.
- Strobilus: enhance for dispersal. In sporophyte. Eg. club moss.
- Sorus: enhance for dispersal. In sporophyte. Only in fern.