Minisymposium 15: Pollen Biology

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Abs # M1504: The mechanical principle behind the virility of the pollen tube

Presenter:	Geitmann, Anja       Contact Presenter
Authors	Geitmann, Anja  (A)
Affiliations:	(A): University of Montreal

On its way to the ovary, a pollen tube needs to penetrate the stigma and the transmitting tissue of the receptive flower. While it uses cell wall digesting enzymes and induction of programmed cell death to soften this growth matrix it still needs to exert a certain invasive force to "drill" its way towards the ovule. The tube also needs to maintain its cylindrical shape against external pressure until the male germ unit has passed. We are interested in the mechanics of this extremely rapid cellular growth and invasion process. We investigate the physical properties of the cellular features that determine cellular mechanics: the turgor pressure, the deformability of the cell wall, and the cytoskeleton. Using miro-indentation we have revealed that apical growth depends on the presence of a gradient in the physical properties of the cell wall along the longitudinal axis. We identified the cell wall components that are responsible for this gradient - pectin and callose. We also studied the mechanical role of the cytoskeletal elements for cellular elongation and for the application of an invasive force. To this end we have developed an in vitro "penetration assay" that allows us to quantify the pollen tube's capacity to invade a mechanical obstacle. Our data illustrate that because of its rapid growth and its invasive "way of life" the pollen tube is an excellent model system for the investigation of the physico-structural roles of the cytoskeleton and cell wall in the mechanics of plant cell growth.