Carpellary Outgrowth Development in the Endocarp of Grapefruit, Citrus paradisi (Rutaceae)

The development and function of the carpellary outgrowth was investigated in grapefruit. Carpellary outgrowths were initiated 3 d postanthesis. By 7 d postanthesis, enlarged globose cells developed that were subtended by a parenchymatous stalk. Numerous Golgi, Golgi-derived vesicles, endoplasmic reticulum, mitochondria, and thickened cell walls present in globose cells from 7 d to 3 mo postanthesis suggest that the carpellary outgrowth was secretory in nature. Lectin-gold complex binding indicated that the secreted product contained galactose and arabinose. Cessation of secretory activity, marked by protoplast degeneration, occurred between 3 and 5 mo postanthesis.