Developmental and Structural Section
Wright, Harrison , Gunawardena, Arunika N. .
In vivo Cellular – level changes in Lace Plant (Aponogeton madagascariensis) Leaves undergoing Developmental Programmed Cell Death (PCD).
During lace plant development discrete populations of cells enclosed by longitudinal and transverse veins (centre cells) undergo PCD, whereas cells within 5 cell layers of the veins (control cells) do not. In this study, observations were made using both light and transmission electron microscopy. During the ‘window formation’ stage of development, control cells continued to divide and expansion was periclinal to the veins; centre cells were stretched in all directions thereby increasing cross-sectional area while decreasing volume. The average chloroplast area and numbers observed on the surface of epidermal cells, as well as the starch grain size and numbers observed on these chloroplasts, declined during the course of PCD (p < 0.001). Chloroplasts continued to divide, even as they decreased in size, until the late stages of PCD. The number of cytoplasmic strands appeared to increase during the middle stages and then decreased during the late stages of PCD (p < 0.001). Cytoplasmic streaming of mitochondria continued during the course of PCD, but ceased just prior to plasmolysis and appeared to coincide with tonoplast rupture; chloroplasts continued to stream during PCD, but those organelles remaining during the later stages were often clustered around the nucleus. Objects, identified as chloroplasts, were observed in increasing numbers undergoing Brownian motion inside the vacuoles in centre cells undergoing PCD, but this form of autophagy was rare in healthy control cells. Interestingly, in detached leaves that continued to grow while floated in distilled water, autophagy of the control cell chloroplasts increased over time, apparently due to low-nutrient stress, not developmental PCD, but to a lesser degree than observed in the centre cells (p < 0.001). This unique plant is an excellent model of developmental PCD in plants, yet much work remains with this novel system to better understand the morphological changes that occur during PCD.
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1 - Agriculture and Agri-Food Canada, Atlantic Food and Horticulture Research Centre, Kentville, NS, B4N 1J5, Canada
2 - Dalhousie University, Biology, 1355, Oxford Street, Life Science Center, Halifax, NS, B3H 4J1, CANADA
Programmed Cell Death
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2008
Time: 8:00 AM