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MIA Talks

Patterns on pollen: a polysaccharide phase transition process (Note: 11am start)

November 18, 2020
Mahadevan Group, Harvard University

Pollen grain surface morphologies are famously intricate and diverse. Every species of pollen-producing plant displays a unique pollen surface pattern that is perfectly replicable, yet an understanding of how these patterns are formed has not been elucidated. We show electron microscopy evidence that these patterns are templated by a phase separation of a polysaccharide mixture on the cell membrane surface. Here we present a modified Landau-Ginzburg model of phase transitions to ordered states that describes these pollen morphologies. We show that 10% of all morphologies can be characterized as equilibrium states with a well-defined wavelength of the pattern. The rest of the patterns have a range of wavelengths on the surface resembling a more “disordered” pattern that can be recapitulated by exploring the evolution of a conserved dynamics model. Through these two models, we show that our theory of phase transitions to modulated surfaces describes the two kinds pollen surfaces morphologies and highlights how these patterns may be mathematically characterized by a few phenomenological parameters.