forms of asexual reproduction in plants. clonal growth (revisited) rhizome stolon suckers plantlets...

Forms of Asexual Reproduction

in Plants

Clonal Growth (revisited)Rhizome

Stolon

Suckers

Plantlets

Bulbils

Fragmentation: jumping cholla

Agamospermy

Production of seeds with no fertilization

Key Stages in the Life-History of a Plant

Growth

Flowering

Pollination

Seed Maturation

Dispersal

Dormancy

Germinationse

ed

ph

ase

Sexual

Reproduction in

Plants

Typical Angiosperm Lifecycle

Alternation of generations

• Sporophyte (2n)

• Gametophytes (1n)

Typical Angiosperm Lifecycle

Alternation of generations

• Sporophyte (2n)

• Gametophytes (1n)

Fertilization

♂♀

Hermaphrodites

Gender Expression in Plants

Sequential Hermaphrodism

Jack-in-the-pulpet (Arisemea triphyllum)

Some plants change sex over time!

Distribution of Flower Types

Variability in Flowering Patterns

• Semelparity

• Iteroparity

Flower once and die

Flower many times

Semelparity: A closer look

Annuals

Biennials

Biennial plant

Year 1 Year 2

© R. Jackson © R. Jackson

Semelparity: A closer look

Big bang perennials

Bet Hedging

Big bang

Vegetative reproduction

Semelparity vs. Iteroparity

Tradeoffs in Phenology of Flowering

Annuals PerennialsBig Bang

Advantages

• Quick reproduction

• Protected as seed

Disadvantages

• High environmental risk

• Poor competitors

Special Circumstances

• Poor conditions for extended time periods

• Strong signal for breaking seed dormancy

Advantages

• Increased size

• Reproduce when resources are plentiful

Disadvantages

• Slower initial population growth

• Require relatively stable habitats

Special Circumstances

Advantages

• Increased fecundity*

• Predator satiation

Disadvantages• Delayed reproduction

• “All eggs in one basket”

Special Circumstances• Can succeed in situations with high stress, low resources

• Better competitor*

* (vs. annuals)

• Unpredictable resource for seed predators

A Majority of Plants are Iteroparous Perennials

Key Stages in the Life-History of a Plant

Growth

Flowering

Pollination

Seed Maturation

Dispersal

Dormancy

Germinationse

ed

ph

ase

The Ecology of PollinationPassive Modes

Wind Pollination Pollination via water

General Considerations Regarding Passive Modes of Pollination

• Requires high levels of pollen production

• Little energy expended on producing intricate flower structures

• Most effective for plants growing at high density

• Risky at low density due to low probability of success

Dispersal Profiles for Wind Born Pollen

Plantago lanceolata

Active Modes of Pollen Delivery: Directed Pollination

Insects

Birds

Bats

Costs Incurred in Employing Pollen Vectors

Rewards

• Fragrance• Nectar• Pollen

Advertising

• Flower color• Flower shape• Fragrance

Bottom line: Pollinators benefit from the incentives provided; not from the services they give to plants

Bottom line: Pollinators benefit from the incentives provided; not from the services they give to plants There are some cheaters!

Movement of Pollen by an Animal Vector

Only measures first visit