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

Douglas fir (Pseudotsuga menziesii (Mirb.) France) pollen stored at low moi sture content experiences imbibition shock when put directly onto culture m edia. This can be overcome by rehydrating the pollen in 100 % relative humi dity prior to culturing. The long-term effect of rehydration on pollen tube growth was investigated. The impact that osmoticants such as sucrose and p olyethylene glycol (PEG) have on pollen elongation and tube formation was a lso studied, using culture media of increasing osmotic potentials obtained with different sucrose/PEG ratios. Rehydration not only improved survival a nd 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 r ange of osmotic potentials (-0.73 to -1.88 MPa). Depending on the sucrose/P EG ratio, between 5 and 55 % of grains produced tubes. There was also a med ia effect on tube morphology. ((C) Inra/Elsevier, Paris.).