Plant Reproductive Biology Michael G. Simpson What is it? Study of sexual and asexual reproduction Pollination mechanisms Gene flow Genetic variation Propagule.

Plant Reproductive BiologyMichael 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 systemsOutbreeding = outcrossing / allogamy / xenogamy:

2) Difference in timing of floral parts = dichogamy

protandry - male first

protogyny - female first

Breeding systemsOutbreeding = 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

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)

Outbreeding = outcrossing / allogamy / xenogamy:

3) Spatial separation of anthers and stigmas = hercogamy

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

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?