Developmental and Structural Section
Conway, Stephanie , Drinnan, Andrew .
Surface analysis of cell division in the shoot apical meristem of gymnosperms.
The shoot apical meristem is a complex structure, and the network of controls that are responsible for the maintenance and productivity of the meristem are still far from being understood, particularly in gymnosperms. In order to interpret underlying genetic and mechanical processes at work, a comprehensive understanding of the cellular development of the SAM is required. Here we present detailed surface analyses from 35 species of gymnosperms using confocal microscopy of whole mount SAMs. Two main processes of growth were identified. Firstly, at the summit of the apical dome, a right-angle type of cell division is the most common pattern in the apical initials and their derivatives. This type of cell division is where daughter cells tend to divide perpendicular to the previous division, so that the new cell walls are at right angles to each other. Related packets of two, three or four daughter cells commonly occupy the summit of the dome. The second type of growth occurs on the periphery of the apical dome, where growth takes on a different form. Here proximal derivatives of the apical initials begin to divide parallel to the previous division to form long axial chains. Development patterns across the whole apical dome proceed differently depending on the size and shape of the meristem. Small and tall apices often maintain a single packet of up to four cells on the summit, which produce only a small number of periclinal divisions, and very little surface development. Medium apices commonly have four or more packets of three or four in their summit zone, all of which can proliferate extensively on the surface as well as contribute to internal growth. The largest and flattest apices have numerous packets of two to four cells occupying a large summit zone and many of cells are dividing periclinally. These detailed surface analyses have revealed patterns of cell division that clarify how growth precedes from apical initials and how the shape of the meristem influences the distributions of growth. Variation in these patterns across different gymnosperms appears related to the shape and size of the meristem with little correlation to phylogenetic relationships.
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1 - The University of Melbourne, School of Biosciences, Parkville, Melbourne, VIC, 3010, Australia
Shoot apical meristem
Apical meristem development
Cell division patterns
Confocal Microscopy .
Presentation Type: Oral Paper:Papers for Sections
Location: Salon 11/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 1:30 PM
Candidate for Awards:Katherine Esau Award,Maynard F. Moseley Award