Meeting Abstract

90.5  Wednesday, Jan. 7  Tip growth of pollen tubes CAMPAS, O*; MAHADEVAN, L; Harvard University; Harvard University ocampas@seas.harvard.edu

Plant cells have the ability to remodel their shape while sustaining an internal turgor pressure that can reach values up to 10 atmospheres. This is achieved by a tight and simultaneous regulation of cell wall assembly and mechanics. It remains unclear though how the interplay between mechanics and growth shapes the cell. We address this question in the particularly simple geometry of tip growth, which consists of the assembly and expansion of cell wall at the apical region of a cylindrically shaped tubular structure. Specifically, we theoretically describe the tip growth of pollen tubes accounting for both the mechanical properties of the cell wall and its assembly process. The observed irreversible expansion of the cell wall during growth is modeled as the extension of a viscous fluid shell under the action of turgor pressure, similarly to the process of glassblowing. Both the radius of the pollen tube and its growth velocity are derived in terms of the relevant physical parameters, as the turgor pressure or the secretion rate of new cell wall material. Identifying these parameters is essential to understand what magnitudes cells might regulate during morphogenesis. We show that although pollen tube shapes may depend on many details, their variability can be understood with a single dimensionless parameter that characterizes the interplay between cell wall assembly and expansion. Our description provides a framework to understand the shape variability observed in tip growing cells of different species, both in plants (pollen tubes, root hairs, et cetera) and fungi (hyphal growth).