From canonical to new model systems: The future of plant development
Kirchoff, Bruce .
Visual Characters in Floral Development.
Recent work on visual character description has established methods for extracting character data from otherwise intractable sources, such as developmental sequences. The methods are based on photographs of homologous developmental stages that are arranged into groups representing the phylogenetic relationships among the taxa based on a specific organ and developmental stage(a specific character). The groups may be hierarchically arranged, allowing for multiple levels of data extraction from the same sets of images. These types of visual character description methods avoid many of the problems that arise from the application of verbal labels, problems that include difficulty in representing variation in character states, and the inability to capture information that can be easily seen but that is hard to describe. This type of information includes information on the relationships among the parts of the organs at that developmental stage. The use of visual character creation methods can be impeded by a failure to consider the context in which the developmental stage occurs, and by heterochronies that change the sequence of development. For instance, the mechanism by which mature floral orientation is achieved in the Zingiberales varies among taxa. Normal patterns of organ initiation are sometimes modified so that floral orientation at the time of initiation is "abnormal." In other cases, floral orientation is adjusted late in development through movements of the pedestal (resupination). In cases where floral orientation changes late in development, early patterns of floral organ initiation often follow those in other monocotyledons. In cases where floral orientation is modified from early development, patterns of organ initiation may differ significantly from these patters. Taking floral orientation in the developing inflorescence into account allows for correct homology assessments,and provides a way to extract novel phylogenetic signal from developmental data. Heterochronies that change the sequence of organ initiation also affect the ability to establish visual characters. In the Zingiberales the sequence of stamen/staminode initiation is different in the banana and ginger groups of families. The sequence in the banana families is more normal, with the outer androecium initiated before the inner. In the ginger families the inner androecium is initiated before the outer. The change is so great that it is impossible to establish visual homologies between among all of the floral primordial at this stage of development. Separate characters must be defined for each group of families.
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1 - University Of North Carolina At Greensboro, Department Of Biology, PO BOX 26170, GREENSBORO, NC, 27402-6170, USA, 919-304-2991
Presentation Type: Symposium or Colloquium Presentation
Location: Delaware A/Hyatt
Date: Wednesday, July 11th, 2012
Time: 2:15 PM