BIOA02H3 Lecture Notes - Lecture 9: Pollen Tube, Inbreeding Depression, Pollination
BIOA02 Module 1 Lecture 9: From Tree to Seed
Temporal/Spatial Separation and Selfing
• Selfing accidents still happen
• Male phases are on the bottom and more mature and open earlier
• Female phases are on top and younger and open later
Self-Incompatibility
• No fertilization with own pollen!
• Biochemical self-recognition
• One way to shut down pollen tube is to close down tube with its own pollen
o Rejection of own pollen can happen in three stages
Multiple Flowering Adaptations at once
• Temporal/spatial and self-incompatibility
• Ease of pollen pickup and delivery → better mechanics
• Self-incompatibility is the ultimate self-avoidance!
Flowers
• Ingenious solution of angiosperms → non-directed and directed mobility of pollen to
seek egg
• Today: extreme diversity in the types of flowers → invention of flowers: triggered largest
diversity of plants ever
Forces behind the evolution of flowers
Main forces
• Assurance of seed set: sheer mechanics, bring female and male gametes together to at
least replace the two parents
• Inbreeding avoidance: create high-quality offspring (do it yourself → inbreeding
depression)
Pollination Syndromes
• Specialization on a narrow set of pollinators
• Use of many different pollinator groups
• Abiotic pollination (wind, water)
o Specialization
▪ Of floral architecture to optimize pollen uptake and deposition
▪ On sense of pollinators for precise attraction (sight, smell, touch)
▪ On food requirements of pollinators (fitting rewards)
▪ Shape, colour, odor, reward
▪ undirected
• Biotic pollination (animals)
o directed
Generalist Pollinators
• Opportunistic flowers
o multiple flowers making up landing platforms for insects of different sizes to roam
o non-specialized food; pollen and nectar
Wind Pollination
• 10% of all plants are wind pollinated
• Wind pollination more common in/at
o Higher latitude and altitude
o Dry environments
o Open vegetation
o Island floras
▪ Habitats with fewer insects or generally more wind
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Document Summary
Bioa02 module 1 lecture 9: from tree to seed. Temporal/spatial separation and selfing: selfing accidents still happen, male phases are on the bottom and more mature and open earlier, female phases are on top and younger and open later. Self-incompatibility: no fertilization with own pollen, biochemical self-recognition, one way to shut down pollen tube is to close down tube with its own pollen, rejection of own pollen can happen in three stages. Multiple flowering adaptations at once: temporal/spatial and self-incompatibility, ease of pollen pickup and delivery better mechanics, self-incompatibility is the ultimate self-avoidance! Ingenious solution of angiosperms non-directed and directed mobility of pollen to seek egg: today: extreme diversity in the types of flowers invention of flowers: triggered largest diversity of plants ever. Main forces: assurance of seed set: sheer mechanics, bring female and male gametes together to at least replace the two parents. Inbreeding avoidance: create high-quality offspring (do it yourself inbreeding depression)
