112
A. D. BONEY
chemical nature of the extracted polysaccharides with taxonomic
relationships within the red algae. Thus Stoloff and Silva (1957) stated
that the agars, carrageenans and gelans were the three principalextractives, and whilst there might be wide variations in the properties within
a polysaccharide type, in no instance was there another type of polysaccharide present. Subsequently Stoloff (1962) expanded this work.
With the carrageenans it has been found that the kappa-fraction is
similar to the agarose of agar, consisting of anhydro-D-galactose and
with sulphate esters in the galactose moieties ; the lambda-fraction is a
linear polymer of D-galactose sulphate. The gelans are similar to
kappa-carrageenan, but with a lower sulphste content. These compounds were identified in seventy-one species of red-algae belonging to
the orders Gelidiales*, Cryptonemiales and Gigartinales, and the
results of this analysis are summarized in Table I. Because of the
specific nature of the extractives, Stoloff suggested that a system of
classification might be devised using biochemical differences as opposed
to those based on reproductive structures and post-fertilization
changes. Thus all plants producing agar should be placed in the order
Gelidiales; all those which yield carrageenans to be placed in the
Gigctrtinales, and the gelan-producers to be placed in a new order, the
Hypneales. As can be seen from Table I, this would imply a radical
revision of the present status of some orders in the red algae, and
indicates a novel approach to taxonomic problems in the red algae
which will repay investigation. I n passing, it is worth noting that
Schmid (1960) listed fifty-one species of red algae from which agar can
be extracted, including two in the genus Ceramium. A further sixteen
species were mentioned as sources of carrageenan. Since the Ceramiales
is one order which appears well established in the red algae (Dixon,
1963a), the significance of changes involved in a biochemical type of
classification is clearly evident.
These polysaccharides are of functional significance in the
plant as a matrix within which the cells are embedded, and as such
play a major role in control of pH, salinity changes in the immediate
environment of the cell (Stoloff, 1962) and protection from physical
damage through the pounding action of waves. The carrageenans
of Qigartkna and Chndrus show a seasonal change in physical properties
(Marshall et al., 1949 ; aee also p. 210), and porphyran, the extractive
from Porphyra, has been found to show Merent gelling properties with
plants from exposed habitats from those growing in shelter (Rees and
Conway, 1962). A comprehensive review of the mucilages of rad algae
has been given by O’Colla (1962).
* See footnote on Table I.
A. D. BONEY
chemical nature of the extracted polysaccharides with taxonomic
relationships within the red algae. Thus Stoloff and Silva (1957) stated
that the agars, carrageenans and gelans were the three principalextractives, and whilst there might be wide variations in the properties within
a polysaccharide type, in no instance was there another type of polysaccharide present. Subsequently Stoloff (1962) expanded this work.
With the carrageenans it has been found that the kappa-fraction is
similar to the agarose of agar, consisting of anhydro-D-galactose and
with sulphate esters in the galactose moieties ; the lambda-fraction is a
linear polymer of D-galactose sulphate. The gelans are similar to
kappa-carrageenan, but with a lower sulphste content. These compounds were identified in seventy-one species of red-algae belonging to
the orders Gelidiales*, Cryptonemiales and Gigartinales, and the
results of this analysis are summarized in Table I. Because of the
specific nature of the extractives, Stoloff suggested that a system of
classification might be devised using biochemical differences as opposed
to those based on reproductive structures and post-fertilization
changes. Thus all plants producing agar should be placed in the order
Gelidiales; all those which yield carrageenans to be placed in the
Gigctrtinales, and the gelan-producers to be placed in a new order, the
Hypneales. As can be seen from Table I, this would imply a radical
revision of the present status of some orders in the red algae, and
indicates a novel approach to taxonomic problems in the red algae
which will repay investigation. I n passing, it is worth noting that
Schmid (1960) listed fifty-one species of red algae from which agar can
be extracted, including two in the genus Ceramium. A further sixteen
species were mentioned as sources of carrageenan. Since the Ceramiales
is one order which appears well established in the red algae (Dixon,
1963a), the significance of changes involved in a biochemical type of
classification is clearly evident.
These polysaccharides are of functional significance in the
plant as a matrix within which the cells are embedded, and as such
play a major role in control of pH, salinity changes in the immediate
environment of the cell (Stoloff, 1962) and protection from physical
damage through the pounding action of waves. The carrageenans
of Qigartkna and Chndrus show a seasonal change in physical properties
(Marshall et al., 1949 ; aee also p. 210), and porphyran, the extractive
from Porphyra, has been found to show Merent gelling properties with
plants from exposed habitats from those growing in shelter (Rees and
Conway, 1962). A comprehensive review of the mucilages of rad algae
has been given by O’Colla (1962).
* See footnote on Table I.