BIOL10005 Lecture Notes - Lecture 24: Aridification, Plant Breeding, Double Fertilization
15 Aug 2018
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Document Summary
* flowering plants reproduce in flowers (conifers reproduce in cones) * origin in early cretaceous (130 million years ago); dominant by 65 million years ago) * flowers are to attract pollinators (to secure sex) * adaptations of angiosperms: double fertilization, xylem vessels, companion cells, flowers appear. What adaptive features account for angiosperm diversity & dominance: vegetative or morphological features. * division of labour in xylem and phloem. * vessels in xylem: large, thin-walled, with open ends continuous piping system. Angiosperms also have tracheids like previous plants (e. g. conifers) which are helpful for water piping & strength (they also have growth rings) * sieve cells (no nuclei) controlled by companion cells (with nuclei) in phloem: reproductive features. * double fertilization (one gives rise to the embryo, the other gives rise to the endosperm food reserves, but only if fertilized) * pollination - diverse mechanisms (e. g. wind, insects); many are specific.
