Ultrastructural Changes in Germinating Lily Pollen

Abstract

Intracellular rearrangements during the onset of pollen tube germination were studied at the ultrastructural level in germinating lily (Lilium longiflorum) pollen. Extensive changes in the endomembrane system included dispersal of the endoplasmic reticulum away from an initial peripheral position, appearance of dictyosomes, reduction in size and number of single-membrane organelles, and loss of the contents of these organelles. After appearance of dictyosomes, there was a decrease in number of cisternae per dictyosome and an association of secretory vesicles with each dictyosome. Other changes included movement of mitochondria, change in form of mitochondria, and synthesis of starch in proplastids. These organelle changes may account for the lag period which preceded pollen tube emergence and rapid tube growth.

Key Words:

• Lilium
• pollen
• ultrastructure