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Transcript
Plant Reproductive Biology Michael G. Simpson What is it? Study of sexual and asexual reproduction Pollination mechanisms Gene flow Genetic variation Propagule dispersal Why study it? Insight into adaptive significance & homology of systematic characters Insight into delimitation of species and subspecies. Sexual Reproduction Non-seed plants Seed plants: Pollination - transfer of pollen from microsporangia to stigma (angiosperms) or ovule (gymnosperms) Wind pollination - ancestral (all gymnosperms) Animal pollination - derived for angiosperms Some angiosperms secondarily wind pollinated Fertilization - fusion of sperm and egg ––> embryo (new sporophyte) Strategy of animal pollination: Attractant & Reward Attractant Visual perianth stamens (e.g., Myrtaceae, Mimosoideae) staminodes (e.g., Zingiberaceae, Cannaceae) corona (e.g., Narcissus) inflorescence Olfactory - usu. from perianth sweet rotten (foul/fetid) - e.g., fly pollinated flowers Strategy of animal pollination: Attractant & Reward Reward Nectar Pollen Waxes Resins or “Trick” instead of a “Treat” Insect trapped (Aristolochia) or drowned (Nymphaea sp.) Mimicry E.g., fooling male insect into “mating” with orchid Pollination Mechanisms INSECT (entomophily) Bees (melittophily/hymenopterophyly): fls. showy, colorful, fragrant, with: nectar guides landing platforms Butterflies (psychophily): fls showy, colorful, fragrant no nectar guides long tubes or spurs Pollination Mechanisms Moths (phalaenophily): large, white, fragrant no nectar guides usually tubes or spurs Pollination Mechanisms Flies (sapromyiophily) maroon / brown in color foul smelling (like rotting flesh) Pollination Mechanisms Birds (ornithophily): red (often, not always) tubular (often) Pollination Mechanisms Bats (cheiropterophily): nocturnal anthesis large, colorful or white produce copious nectar or pollen Pollination Mechanisms Wind (anemophily): flowers small, numerous, often unisexual perianth absent or non-showy flowers often produced in mass Pollination Mechanisms Water (hydrophily): Breeding systems Outbreeding versus Inbreeding vs. in-between Breeding systems Outbreeding = outcrossing / allogamy / xenogamy: How is it promoted? 1) Plant sex: dioecy (incl. gynodioecy, androdioecy, trioecy) Breeding systems Outbreeding = outcrossing / allogamy / xenogamy: 2) Difference in timing of floral parts = dichogamy protandry - male first protogyny - female first Breeding systems Outbreeding = outcrossing / allogamy / xenogamy: 3) Spatial separation of anthers and stigmas = hercogamy heterostyly: different style/stigma & correlated anther heights Outbreeding = outcrossing / allogamy / xenogamy: 3) Spatial separation of anthers and stigmas = hercogamy enantiostyly: left & right-handed flowers Outbreeding = outcrossing / allogamy / xenogamy: 3) Spatial separation of anthers and stigmas = hercogamy movement hercogamy: trigger mechanisms Outbreeding = outcrossing / allogamy / xenogamy: 3) Spatial separation of anthers and stigmas = hercogamy movement hercogamy: e.g., stigma movement Diplacus [Mimulus] aurantiacus (Phyrmaceae) Folding of style best explained as adaptation to reduce interference in bird pollination Outbreeding = outcrossing / allogamy / xenogamy: 4) Self-incompatibility Genetically determined, inability for fertilization to occur between gametes derived from one individual. Inbreeding = selfing autogamy (w/in 1 flower) & geitonogamy (between fls. of 1 indiv.) Selective advantage: ensures propagule production Disadvantage: reduced to absent genetic variability allautogamy: both outcrossing & inbreeding e.g., Viola, Clarkia: two flower types: chasmogamous flowers - normal, open cleistogamous flowers - remain closed Fruit/seed dispersal Wind - samaras, winged seeds Water - e. g., Cocos nucifera (Arecaceae) Explosive dehiscence Self (Autochory, e. g., Arachis hypogaea) Animal Asexual Reproduction Vegetative reproduction: ramets Rhizomes Bulbs, bulbels Corms, cormels Plantlets Asexual Reproduction Agamospermy - seed production without fertilization Parthenogenesis (diploid egg) Adventive polyembryony (non-egg diploid cell) Hybridization in plants Polyploidy – evolution of multiple sets of chromosomes; major mechanism of speciation. Hybridization in plants Common Can produce sterile, vegetatively reproducing species (e. g., certain cacti) Testing for breeding mechanisms 1) Control 2) Caged, self-pollinated 3) Caged, left alone 4) Emasculated, caged 5) Caged, emascul., outcrossed A + + B + + + C + + + + D + + + + + What is the breeding mechanisms for species A, B, C, D?
