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Ch 30 - Plant Diversity II (1 slide per page)-1

1 tube cell pollen tube 1 generative cell sperm 2

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Unformatted text preview: ophytes - Made of only FOUR cells! - 1 tube cell (pollen tube) - 1 generative cell (sperm) - 2 prothallial cells (sterile; ? function) - Does NOT have an antheridium - sperm form from generative cell Prothallial cells 41 Pollen tube formation & spermatogenesis • After pollen grain arrives near ovule it begins to develop. • Tube cell divides into pollen tube which grows toward developing egg in archegonium of ♀ gametophyte • Generative cell moves to tip of tube and divides into 2 sperm (mitosis) TAKES ONE YEAR While this happening… Sperm nucleus Female cone 42 At time of pollination ovule is immature (and so is ♂ gametophyte in pollen) (2n) Megasporophyll Ovule = Megasporangium + integument (2n) Pollen grain reaches ovule & pollen tubule burrows through ovule wall to megaspore inside. Pollen near ovule Figure 30.6 (4) (Campbell et al.) Megaspore (2n) 43 Ovule maturation Megasporangium (2n) Megaspore (n) TAKES ONE YEAR female gametophyte (n) Egg (n) (in archegonium) Megaspore (n) in megasporangium develops into female gametophyte (n) which produces egg (gamete)(n) in archegonium (gametangium) Figure 30.3 and 30.6 (Campbell et al.) 44 Fertilization occurs one year after pollination POLLINATION FERTILIZATION Figure 30.6 (Campbell et al.) 45 From Ovule to Seed Seed = Sporophyte Embryo (2n) + food supply (n) + seed coat After fertilization, seed takes ONE more YEAR to complete development • Fertilized egg (zygote)(2n) develops into embryo (multicellular 2n) (embryo = new sporophyte) • Female gametophyte tissue becomes food for embryo Figure 30.3 (Campbell et al) 46 Seed dispersal occurs a minimum of: POLLINATION • One year after fertilization • Two years after pollination DISPERSAL...
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