Lecture - Oct 19

Lecture - Oct 19 - Bio 10/19/09 Ferns Largest and most...

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Bio 10/19/09 Ferns - Largest and most diverse group of seedless vascular plants - Sporophyte (2n) consists of a rhizome (underground stem) that bears megaphylls and true roots - Use water as a transport system o Flagellate sperm swim from thallus to neck of archegonium via a thin film of water Wisk ferns: - Sporophytes (2n) have dichotomously (equal) vertical aerial stems o Do not have true roots o Fern Life Cycle (fig) Fern Gametophytes (n) Prothallus develops from haploid spore; bears both archegonia and antheridia Fern Sporophytes (2n) Plant with roots, rhizomes, leaves are megaphylls Leave (fronds) bear sporangia in clusters (sori). Meiosis in sporangia produces haploid spores Horsetails - Reproductive sporophytes (2n) have o Hollow, jointed aerial stems, impregnated with silica (gritty) o Rhizomes, strobili o Leaves are reduced megaphylls o Green stem is the main organ of photosynthesis - Also have non-reproductive (vegetative) shoots - Used as scourers to scrub pots and pans Calamites (ancient) had underground rhizome where roots and aerial shoots originated Equisetum; unbranched reproductive shoots, bearing conelike strobili (see table 27-2) Homospory - Sporangium (2n) produces one kind of spore as a result of meiosis:
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o In bryophytes, most club mosses, most ferns including whisk ferns and horsetails - Each gametophyte (n) can produce both egg cells and sperm cells Heterospory - Production of two types of spore (male and female); give rise to two types of gametophyte: o Male microspores and female megaspores form in one sporangium (sporophyte) - In some club mosses (Selaginella) and ferns, and in all seed plants Selaginella (club moss) Life Cycle (see fig) The Plant Kingdom: Seeded Plants (Chapter 28) - While most seedless plants are homosporous, all seeded plants are heterosporous , producing both microspores and megaspores. -
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Lecture - Oct 19 - Bio 10/19/09 Ferns Largest and most...

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