title: Vesicles between plasma membrane and cell wall prior to visible senescence of Iris and Dendrobium flowers.
abstract: Cut Iris flowers (Iris x hollandica, cv. Blue Magic) show visible senescence about two days after full opening. Epidermal cells of the outer tepals collapse due to programmed cell death (PCD). Transmission electron microscopy (TEM) showed irregular swelling of the cell walls, starting prior to cell collapse. Compared to cells in flowers that had just opened, wall thickness increased up to tenfold prior to cell death. Fibrils were visible in the swollen walls. After cell death very little of the cell wall remained. Prior to and during visible wall swelling, vesicles (paramural bodies) were observed between the plasma membrane and the cell walls. The vesicles were also found in groups and were accompanied by amorphous substance. They usually showed a single membrane, and had a variety of diameters and electron densities. Cut Dendrobium hybrid cv. Lucky Duan flowers exhibited visible senescence about 14 days after full flower opening. Paramural bodies were also found in Dendrobium tepal epidermis and mesophyll cells, related to wall swelling and degradation. Although alternative explanations are well possible, it is hypothesized that paramural bodies carry enzymes involved in cell wall breakdown. The literature has not yet reported such bodies in association with senescence/PCD.
authors.affiliation: Department of Horticulture, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand.
authors.forename: Channatika
authors.initials: C
authors.lastname: Kamdee
authors.affiliation: Department of Horticulture, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand.
authors.forename: Kanjana
authors.initials: K
authors.lastname: Kirasak
authors.affiliation: Department of Horticulture, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand; Academy of Science, The Royal Society, Dusit, Bangkok 10300, Thailand. Electronic address: agrsck@ku.ac.th.
authors.forename: Saichol
authors.initials: S
authors.lastname: Ketsa
authors.affiliation: Mann Laboratory, Department of Plant Sciences, University of California, Davis, CA 95616, USA.
authors.forename: Wouter G
authors.initials: WG
authors.lastname: van Doorn
mesh_terms: D017209:Apoptosis; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002473:Cell Wall / Q000378:metabolism / Q000648:ultrastructure; D022162:Cytoplasmic Vesicles / Q000648:ultrastructure; D031667:Dendrobium / Q000502:physiology* / Q000648:ultrastructure; D035264:Flowers / Q000502:physiology* / Q000648:ultrastructure; D031323:Iris Plant / Q000502:physiology* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission
keywords: Cell wall degradation; Cell wall enzymes; Cell wall swelling; Programmed cell death; Senescence