Biology Reference
In-Depth Information
Chapter 2
Morpho-functionality of Carbon Metabolism
in Seaweeds
Iv´nG´mez and Pirjo Huovinen
2.1
Introduction
The process by which inorganic carbon is converted into organic forms driven by
the solar energy is unique to photoautotrophic organisms (some types of
prokaryotes, cyanobacteria, eukaryotic algae, and plants). Although in many
cases the underlying mechanisms and enzymatic machinery associated with carbon
metabolism are essentially similar to those found in higher plants, seaweeds show
some differences, especially related with carbon acquisition and concentration,
biochemical strategies to avoid the oxygen/CO 2 interference of RUBISCO (photo-
respiration), and C4 metabolism. Other striking characteristic lies in the remarkable
versatility of the different biochemical pathways and products that allow seaweeds
to operate under resource limitation (e.g., CO 2 , light, nutrients) and under changing
environments. On the other hand, seaweeds exhibit a great variety of storage
carbohydrates (e.g., mannitol, floridoside). These compounds can be remobilized
during growth and reproduction, and are also normally involved in a series of
reactions associated with osmoregulation and antioxidant activity (see Lobban
and Harrison 2000 for an overview).
Seaweeds are multicellular, macroscopic organisms and thus a major aspect of
carbon metabolism that makes them different from other groups of algae and
cyanobacteria is its dependency on gross morphology. The morpho-functional
processes of carbon assimilation occurring in foliose and finely branched seaweeds
can be considerably different from those of, e.g., coarsely branched and leathery
species (Ramus 1978 ; Rosenberg et al. 1995 ). In many large brown algae, seasonal
decoupling of carbon assimilation and anabolic processes, long-distance transport
of photoassimilates, and biomass formation restricted to meristematic cells are
I. G´mez ( * ) • P. Huovinen
Instituto de Ciencias Marinas y Limnol´gicas, Universidad Austral de Chile, Campus Isla Teja s/n,
Casilla 567, Valdivia, Chile
e-mail: igomezo@uach.cl ; pirjo_huovinen@uach.cl
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