FIGURE 4.

Germination stages of P. volubilis pollen grains using GM, stained using DAPI fluorochrome, and visualized under fluorescent microscopy. (A) (Stage 1), pollen grains not completely germinated, lacking pollen tube and stained directly. (B) (Stage 2), pollen grains showing very conspicuous germination apertures. (C) (Stage 3) pollen partially germinated with an observable migration of vegetative and germinative cells. (D) (Stage 4), pollen grains germinated and conspicuous pollen tubes with male germination unit (MGU) migrating across the tube. Germinative cells are illustrated in vertical arrows, and vegetative nuclei are pointed by the horizontal arrows. A and B were observed at 20X and C and D at 40X.