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Aerodynamics and pollen ultrastructure in Ephedra
Kristina Bolinder1, Karl J Niklas2, Catarina Rydin1
1Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, SE-106 91, Sweden.
American Journal of Botany
|March 19, 2015
Summary
Ephedra foeminea pollen has a fast terminal settling velocity (Ut) and dense ultrastructure, suggesting insect pollination. Unlike wind-pollinated species, its ovules lack adaptations for efficient pollen capture.
Area of Science:
- Paleobotany
- Plant reproductive biology
- Aerodynamics
Background:
- Pollen dispersal relies on terminal settling velocity (Ut), influenced by grain properties and atmospheric conditions.
- Pollen capture by ovulate organs depends on the aerodynamic environment around them.
Purpose of the Study:
- Investigate pollen ultrastructure and Ut of Ephedra foeminea.
- Compare E. foeminea's pollen capture efficiency with anemophilous Ephedra species.
- Determine if E. foeminea is entomophilous or anemophilous.
Main Methods:
- Terminal settling velocity (Ut) measured via stroboscopic photography.
- Aerodynamic acceleration fields around ovules calculated.
- In-flight pollen behavior simulated using computer models.
- Pollen morphology and ultrastructure analyzed with SEM and STEM.
Main Results:
- Pollen wall ultrastructure correlates with Ut in Ephedra.
- Granule proportion in infratectum affects pollen bulk density, Ut, and dispersal.
- Computer simulations showed no traits favoring anemophilous pollen capture in E. foeminea.
Conclusions:
- Fast Ut and dense ultrastructure of E. foeminea pollen suggest entomophily.
- E. foeminea ovules lack the aerodynamic microenvironment for pollen capture seen in anemophilous species.
- Cretaceous Ephedroid palynomorphs with similar ultrastructure may have originated from insect-pollinated plants.
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