Pollination Systems and Reproductive Biology

Pollination

Pollination is the transfer of pollen grains from an anther to a stigma

It is required for sexual reproduction but not for asexual reproduction

Flowers are the focal point for delivery and receipt of pollen

 

Self-pollination vs. Outcrossing

Self-pollination is when pollen from a plant is transferred to a stigma of the same plant, either within a flower or between flowers.

Outcrossing is when pollen from one plant is transferred to the stigma of another

 

Pollination Syndromes are lists of features that are associated with a particular mode of pollination

 

Self Pollination Syndrome

Small, inconspicuous flowers

Usually unpigmented (green or white flowers)

Low pollen: ovule ratio

Anthers positioned close to stigmas

Unscented

Small pollen grains

 

Abiotic Pollination

Wind pollination

Water Pollination

Wind Pollination

 

Wind Pollination Syndrome

Be small and inconspicuous

Have large amounts of tiny pollen grains

Have large feathery stigmas

 

Water Pollination Syndrome

Water pollinated flowers tend to:

Be small and inconspicuous (and submerged or floating)

Have lots of small pollen grains (sometimes floating)

Have large feathery stigmas (sometimes floating)

 

Biotic Pollination
All forms of animal pollinators

INSECTS:

Bees

Butterflies

Moths

Flies

Ants

Wasps

 

NON-INSECTS:

Birds

Bats

Lemurs

Rodents

 

Rewards vs Attractants

REWARDS: Rewards are the things that animal pollinators visit flowers for.

Nectar

Pollen

Resin

Oils

Heat

Fat bodies

ATTRACTANTS: Attractants are the cues that animals use to locate flowers.

Color

Shape

Size

Scent

 

Bee Pollination

Bee-pollinated flowers tend to fall into two classes:

Showy, open, bowl-shaped flowers that are relatively unspecialized

Showy, complicated, zygomorphic flowers that are more specialized

All be flowers tend to be yellow or blue, often with UV nectar guides and scented

 

Butterfly Pollination

Butterfly-pollinated flowers tend to:

be large and showy

be pink or lavender

have long narrow corolla tubes

be scented

 

Moth Pollination

Moth-pollinated flowers tend to:

be large and showy

be white

have tubular corollas

have a sweet scent produced in the evening

 

Fly Pollination

Fly-pollinated flowers tend to:

have a strong unpleasant odor

be brown or orange in color

 

Bird Pollination

Bird-pollinated flowers tend to be:

large and showy

red

tubular

produce a lot of nectar

they usually lack a scent

 

Bat Pollination

Bat -pollinated flowers tend to:

be large and showy

be firm

be white or light-colored

have a strong scent of cabbage or fermented fruit

open at night

 

Pseudocopulation

A pollination system, usually found in orchids, where a flower resembles a female wasp, and the male wasp lands on the flower to try to copulate, fails, and makes the same mistake again.

 

Obligate mutualisms

Yucca/yucca moths

Fig/fig wasps

 

Reproductive Biology

The study of plant reproductive methods such as phenology, breeding systems, pollination, floral structure, and dispersal.

 

Self-incompatibility

The inability of a bisexual plant (hermaphrodite) to produce zygotes from its own pollen.

Two types:

Gametophytic--mating opportunities determined by the genotype of the pollen

Sporophytic--mating opportunities determined by the genotype of the sporophytes (pollen and egg parents).

 

Phenology

The timing of events, particularly in reference to reproductive events.

Any scale from hourly, daily, or annual.

 

Breeding Systems

Systems of sexuality in flowering plants which impact the relative rates of inbreeding or outcrossing.

 

Hermaphroditism

The simplest and most common breeding system is hermaphroditism, where each plant has both female and male functions and all flowers are perfect.

 

Dioecy

Dioecy is the second most common breeding system found in plants; individuals are either female or male and have either staminate or pistillate flowers.

 

Monoecy

Monoecy is the another common breeding system found in plants; individuals are hermaphroditic but lack perfect flowers, instead having both staminate or pistillate flowers.

 

Gynodioecy

The breeding system in which there are two types of plants, females (with pistillate flowers) and hermaphrodites (with perfect flowers).

 

Gynomonoecy

The breeding system in which there is a single type of plant, but with two types of flowers, pistillate and hermaphroditic.

 

Androdioecy

The breeding system in which there are two types of plants, males (with staminate flowers) and hermaphrodites (with perfect flowers).

 

Adromonoecy

The breeding system in which there is a single type of plant, but with two types of flowers, staminate and hermaphroditic.

 

Evolution of Breeding Systems

Hermaphroditism and dioecy are stable systems, the other breeding systems are sometimes thought to be transitory between them.

Generally breeding system evolution is thought to be triggered by inbreeding and inbreeding depression, but resource allocation may also play a role.

 

Dispersal

Movement of plants from place to place, usually in the form of seeds, but sometimes also in the form of pollen.

 

Dispersal is the mechanism through which gene flow occurs.

Dispersal Vectors

Abiotic elements: wind, water, gravity.

 

Biotic elements: animals (by eating, sticking to surface, pollination) or by self dispersal (explosive fruits).