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Seminar Detail
How to make a leaf? 400 million years of repeated answers to the
same evolutionary question
Presenter: Kevin Boyce ()
July 14, 2003 12:00 AM Pacific
The chance to compare multiple repetitions of evolutionary history is
at the heart of astrobiology, but opportunities for such evolutionary
comparisons are already available here on earth. Plants are particularly
attractive for such study: nearly all aspects of land plant form--including
roots, leaves, wood, and reproductive structures--have evolved a number of
times independently and details of plant construction allow the preservation
in fossils of an unusual wealth of biochemical, physiological, and
developmental information.
Leaves have evolved independently in a number of different plant groups
and several basic leaf morphologies have appeared again and again among
fossil and extant lineages. Comparative investigation of living plants has
demonstrated that this morphological convergence has required the convergent
evolution of developmental processes as well. Furthermore, these recurring
morphological and developmental alternatives also appear to represent
physiological alternatives. Opposing strategies are employed in the
different leaf types to ensure an even supply of water to the entire
photosynthetic surface and exploitation of these physiological alternatives
has involved the correlated evolution of changes in anatomy, hydraulic
resistance properties, transport regulation capabilities, and vascular cell
wall chemistry. Therefore, the basic types that can be recognized in fossil
and extant plants represent highly integrated developmental, biochemical,
and physiological syndromes that have evolved repeatedly after divergence
from an extremely simple, leafless common ancestor.
However, nature is also capable of sports that are completely alien to
our expectations. For example, the Devonian-age organism Prototaxites
produced enormous tree-like trunks composed of intertwined, 50 micron-
diameter tubes. This bizarre organism has defied classification for the 150
years since its discovery, but geochemical studies now suggest its
biological affinities are with the fungi. Both of these evolutionary
extremes, convergence and novelty, will be discussed.
Participation Instructions
http://nai.arc.nasa.gov/seminars/instructions.cfm
December 21, 2007
The Director’s Seminar series features talks from scientists who are invited by the NAI Director to present their research results to the community. A primary goal of the seminars is to encourage interdisciplinary collaboration across NAI teams and within the astrobiology community at large.
Team Overview Seminars describe the work of the fourteen NAI teams and NAI Central. They offer an opportunity to find out more about the science, E/PO and other activities being performed by the NAI teams and the NAI Central office.
The Forum for Astrobiology Research (FAR) provides an opportunity for graduate students to present their research results and to meet as a student community for networking and mutual support.
The University of Washington seminar series is hosted by the NAI Virtual Planetary Lab (VPL) team from the UW campus in Seattle.
