Anatomical and histological changes in the fruit abscission zone of water dropwort (Oenanthe stolonifera DC.)

Abstract

Our goal was to investigate fruit abscission in Oenanthe stolonifera DC. by studying the morphological and cytological changes in the abscission zone. One abscission zone existed at the junction between the fruit and the pedicel. The region was clearly distinguishable 10 days after anthesis onwards and consisted of 3 to 5 layers of cells that formed a small, closely packed shape. Cells in the abscission layer began to flatten as the fruit developed. At the beginning of cell separation, cells in the middle area returned to a round shape and adjacent pedicel parenchyma cells enlarged. As abscission began, the cell wall dissolved from the middle lamella. Cell separation gradually extended toward the periphery from the middle area and, eventually, a distinct separation layer was formed. As the process proceeded, abscission zone cells developed large vacuoles and the organelles lost their shape. However, in explants treated with cycloheximide, the cell wall separated from the membrane and a whorled membrane was observed. This finding suggests that structural changes in the cell membrane may help explain the control of fruit abscission in O. stolonifera.