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?