Ion Implantation Hampers Pollen Tube Growth and Disrupts Actin Cytoskeleton Organization in Pollen Tubes of Pinus thunbergii

Pollen grains of Pinus thunbergii Parl.(Japanese black pine) were implanted with30 keV nitrogen ion beams and the effects of nitrogen ion implantation on pollen tube growth invitro and the organization of actin cytoskeleton in the pollen tube cell were investigated usinga confocal laser scanning microscope after fluorescence labeling.Treatment with ion implanta-tion significantly blocked pollen tube growth.Confocal microscopy showed that ion implantationdisrupted actin filament cytoskeleton organization in the pollen tube.It was found that therewas a distinct correlation between the inhibition of pollen tube growth and the disruption ofactin cytoskeleton organization,indicating that an intact actin cytoskeleton is essential for con-tinuous pollen tube elongation in Pinus thunbergii.Although the detailed mechanism for theion-implantation-induced bioeffect still remains to be elucidated,the present study assumes thatthe cytoskeleton system in pollen grains may provide a key target in response to ion beam im-plantation and is involved in mediating certain subsequent cytological changes.