PLASTID DIFFERENTIATION DURING CUCURBITA-PEPO (CUCURBITACEAE) POLLEN GRAIN DEVELOPMENT

The development of plastids in the pollen of Cucurbita pepo was follow ed from meiosis to pollen maturation by quantitative light and electro n microscopy. Plastids are initially undifferentiated, then divide, an d at late microspore stage differentiate into amyloplasts containing s tarch. Later the amyloplasts form lobes and divide, Amyloplasts contai ning a single starch grain are present from the early bicellular stage . Plastid development is considered in relation to such cytoembryologi cal features as the pollen does not dehydrate at anthesis and germinat ion begins 3 min after pollination.