Ultrastructural modifications in pollen grains stored by honey bees (Apis mellifera L.)

SUMMARY

A transmission electron microscopy study of pollen grains from honey collected from hives before being sealed, and from sealed honey, pollen storage cells and from pollen pellets, is reported. The exine was the structure most resistant to change during the storage process. In unsealed honey, the cytoplasm appeared to be perfectly conserved, but it frequently pushed the infine, which protruded noticeably. In sealed honey the cytoplasm had a strong tendency to crystallize and reserve materials such as starch and lipids started to show some symptoms of degradation; the apertures normally appeared closed and the cytoplasm did not protrude in any case. It is suggested that the osmotic pressure of unsealed honey leads to turgescent pressure which causes the cytoplasm to protrude through the apertures, and that the cytoplasm is preserved by pyknosis of the cytoplasmic contents. Pollen grains from storage cells and from pollen pellets appeared to be in an excellent state of conservation.

Keywords:

• pollen
• cytology
• ultrastructure
• honey
• storage
• transmission electron microscopy