BIOL 2P93 Lecture Notes - Lecture 24: Douglas Fir, Mitosis, Thuja Plicata
24 Jan 2016
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15 months after pollination: pollen tube reaches egg cell of archegonium discharge cytoplasm + sperm into egg cytoplasm. 1 sperm nucleus unite w/ egg nucleus, other sperm degenerates. Eggs of all archegonia are fertilized + develop into embyros (polyembryony) , only one embryo will develop fully, (but 3-4 % of pine seeds will have 1+ embryo + make 2-3 seedlings upon germination. Spermatogenous cell of pollen grain makes 2 sperm pollen tubes digest through nucellus to developing megagametophyte. Pollen tubes reach egg cells of archegonia (enclosed w/in megagametophyte) discharging sperm into egg cytoplasm. 1 sperm nuclei fertilizes 1 egg in 1 of archegonia in each of ovules = diploid zygote divide by mitosis to = embryo. : fertilization occur as sperm nucleus unites w/ egg nucleus, second sperm nucleus is non-functional + disintegrate. Early embryo development: 4 tiers of cells made at lower end of each archegonium 4 cells of uppermost tier (farthest away from micropyle) forms an embryo.
