Abstract:

Gymnosperms originated earlier than angiosperms. Elongation in gymnosperms pollen tube exhibits some evolutionarily primitive characteristics, I.e. slow germination and growth, branching and longevity. These differences may be orchestrated by cytoskeletal organization. In the study, microtubule organization in germinated pollen of Pinus thunbergii is investigated using a confocal laser scanning microscope after immunofluorescence labeling. Within germinated pollen, microtubules are arranged obliquely or transversely. In elongated tubes, microtubules are arranged along the longitudinal axis. An enriched microtubules network is presented in the pollen tube tip and has a unique functional role. Following colchicine treatment, the organization of microtubules within pollen tubes is disrupted and the morphology of pollen tubes is changed. Colchicine significantly induces tube tip swelling. Swollen tip is considered to be caused by the disorganization of microtubules in the tip. Our results indicated that microtubules in gymnosperms pollen tube tip play an important role in maintaining tip integrity. The present paper also suggests that microtubules participate in directing tip extension in gymnosperms pollen tube and gymnosperm pollen tubes elongate in a mechanism that is different from angiosperm pollen tubes.

Key words: gymnosperms, Pinus thunbergii, pollen tube, cytoskeleton, microtubules, laser scanning confocal microscope(LSCM)