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

Abstract

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.