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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