chapter 28 The Plant Kingdom

chapter 28 The Plant Kingdom - The Plant Kingdom Seed...

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Unformatted text preview: The Plant Kingdom: Seed Plants · Seeds- reproductive tool with a sporophyte, nutritive tissue, and protective coat · Reasons they are superior to spores: · Contains a multicellular young plant · Contains an abundant food supply · Protected by a multicellular seed coat An Introduction to Seed Plants · All seed plants are heterospores and produce microspores and megaspores · After fertilization the an ovule forms, the megasporangium and its enclosed structure, and develops into a seed · Integuments- layers of sporophyte tissue that surround and enclose the megasporangium. After fertilization takes place, the seed coat develops from this · Gymnosperms- have exposed seeds in the form of scales on cones · Angiosperms- have enclosed seeds in fruits · Xylem- conducts water and dissolved minerals · Phloem- conducts dissolved sugar · Alternation of generations- lifecycle where part of the life is spent in the sporophyte stage and another part is in gametophyte stage; in these plants they are always 2n dominant Gymnosperms · Conifers- woody trees or shrubs that produce annual additions of secondary tissue · Wood/ secondary xylem has tracheids- long, tapering cells with pits through which water and dissolved minerals move from one cell to another · Many conifers produce resin, a viscous, clear or translucent substance consisting of several organic compounds that may protect the plant from attack or by fungi or insects · Most conifers have leaves called needles that are commonly long and narrow, tough, and leathery. Most are evergreen · Most are monoecious- have a separate male and female reproductive parts in different locations on the same plants, usually born on the strobili/cones · Cover a great range of locations and provide food, shelter, and anchor soil · Male pinecones have sporophylls- leaf like scales that bear sporangia on the underside · Base of each has two microsporangia which contain numerous microsporocytes, each which undergoes meiosis to form four haploid microspores which then develop into extremely reduced male gametophytes ( pollen grain) · Female cones- each scale bears two ovules (megasporangia) on its upper surface · Meiosis of megasporocyte produces 4 haploid megaspores . One divides mitotically producing an egg, the other 3 degenerate · Pollination- transfer of pollen to the female cones...
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chapter 28 The Plant Kingdom - The Plant Kingdom Seed...

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