01:119:116 Lecture Notes - Lecture 9: Pollen Tube, Pollen, Sporangium
Document Summary
Derived traits of seed plants: c/c derived traits of seed plants. Angiosperms: c/c angiosperm structures, seq angiosperm reproduction. Already discussed several cuticle preventing desiccation, etc. Seed plants have more adaptations are better adapted for terrestrial life. Reduced gametophyte size = adaptation for land. Production of 2 different types of spores. Ovule megasporangium + megaspore + integuments. Integuments protective sporophyte tissue around megasporangium, forms seed coat. Pollen grain male gametophyte within pollen wall. Protected by a thick sporopollenin wall keeps spores safe and prevents desiccation. Transfer of pollen to part of plant containing ovules. Pollination is not fertilization it is dispersal of male gametophyte. Sperm dispersal is no longer water dependent (most lack flagella) Seedless plants spore is the only protective stage (only thing to disperse) Seeds exposed on modified leaved ex. Mature sporophyte ex: pine tree (2n) Pollen grain reached ovule then germinates. Megasporocyte meiosis 4 haploid cells 1 megaspore female gametophyte with 2-3 archegonia (1 egg each)