Faculty of Science, School of Sciences, Natabua Campus Lautoka BIO706 Embryology Lecture 22: Plant Reproductive Biology - II

Plant Reproductive Biology 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 Visual perianth stamens (e.g., Myrtaceae, Mimosoideae) staminodes (e.g., Zingiberaceae, Cannaceae) corona (e.g., Narcissus) inflorescence Olfactory - usually from perianth sweet smell – e.g. honey bee pollinated flowers rotten (foul/fetid) - e.g., fly pollinated flowers

Strategy of animal pollination: Attractant & 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) Flowers: showy, colorful, fragrant, with: nectar guides landing platforms Butterflies (psychophily) flowers: 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):

Outbreeding versus Inbreeding vs. in-between include Outbreeding versus Inbreeding vs. in-between

Outbreeding = outcrossing / allogamy / xenogamy: How is it promoted? 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

heterostyly: different style/stigma & correlated anther heights Breeding systems Outbreeding = outcrossing / allogamy / xenogamy: 3) Spatial separation of anthers and stigmas = hercogamy heterostyly: different style/stigma & correlated anther heights

enantiostyly: left & right-handed flowers Outbreeding = outcrossing / allogamy / xenogamy: 3) Spatial separation of anthers and stigmas = hercogamy enantiostyly: left & right-handed flowers

movement hercogamy: trigger mechanisms Outbreeding = outcrossing / allogamy / xenogamy: 3) Spatial separation of anthers and stigmas = hercogamy movement hercogamy: trigger mechanisms

movement hercogamy: e.g., stigma movement 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 Allo-autogamy: 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

Vegetative reproduction: ramets Rhizomes Bulbs, bulbels Corms, cormels Asexual Reproduction Vegetative reproduction: ramets Rhizomes Bulbs, bulbels Corms, cormels Plantlets

Agamospermy - seed production without fertilization 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 A B C D 1) Control + + + + 2) Caged, self-pollinated - + + + 3) Caged, left alone - - + + 4) Emasculated, caged - - - + 5) Caged, emascul., outcrossed + + + + What is the breeding mechanisms for species A, B, C, D?

Pollen tube growth through style tissue

Courtesy Michael G. Simpson, internet sources and relevant book chapters Questions are welcome