In vitro Douglas fir pollen germination: Influence of hydration, sucrose and polyethylene glycol

Abstract

Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) pollen stored at low moisture content experiences imbibition shock when put directly onto culture media. This can be overcome by rehydrating the pollen in 100 % relative humidity prior to culturing. The long-term effect of rehydration on pollen tube growth was investigated. The impact that osmoticants such as sucrose and polyethylene glycol (PEG) have on pollen elongation and tube formation was also studied, using culture media of increasing osmotic potentials obtained with different sucrose/PEG ratios. Rehydration not only improved survival and pollen development on all media but also enhanced pollen tube induction and growth on most of them. Douglas fir pollen produced tubes over a wide range of osmotic potentials (-0.73 to -1.88 MPa). Depending on the sucrose/PEG ratio, between 5 and 55 % of grains produced tubes. There was also a media effect on tube morphology.