204
A. D. BONEY
other parts of the plants, and similar results were obtained for the
mannitol, protein and fat contents. ,Evidence was also obtained of
changes in the metabolic rate with growth of the plant, and of different
concentration gradients with age.
The effects of depth of immersion on the chemical composition of
the Laminaria species common to Scotland have been reported by
Black (1960b). In general the variation in the fronds was far more
noticeable than that of the stipes. For Laminaria hyperborea the alginic
acid content showed little significant variation with depth in both stipe
and fronds, and whilst the stipes of L. digktata contained similar
quantities of alginic acid, the fronds had a tendency to show a somewhat
lower content with increasing depth during July, and some measurable
variation was also observed with L. saccharina. The mannitol reserves
were found to increase to depths of 6-10 my and then to decrease. By
contrast, the lamina& content fell progressively with depth. Where
any noticeable fluctuation occured in alginic acid the variation is
usually the inverse of mannitol, in keeping with Bidwell’s (1968)
observations. Differences of this nature are in part due to the degree of
sublittoral illumination, although other factors, probably associated
with available nutrients, are also involved. The most marked differences
were observed during the summer.
Black (1964a) studied concentration gradients in the fronds of
Laminaria sacchurina at Werent seasons. During the rapid growth
period (spring) little variation was observed in the composition of the
tissues along the frond. During the slow-growth period (August), and in
the autumn, considerable variation in chemical composition was
observed because of the variable age of the tissues. At the base of the
frond above the meristematic region, laminarin was absent, and proteins
and alginic acid were of very low value ; mannitol was present, and the
mineral content high. During the period of slow growth the upper twothirds of the lamina contains a reserve of laminarin and proteins, since
this is the period when continued photosynthesis and a reduction in the
rate of cell division leads to a steady accumulation of reserves. The
iodine and fucosterol contents were found to be at a maximum in the
transition region between stipe and frond. A study of chemical and
growth gradients was made also on Laminaria hyperborea (Black et al.,
1960). Lmsen and Haug (1961) investigated the biochemical gradients
in the stipe of Laminaria hyperborea, using the peripheral tissue, the
outer and inner cortex and the medulla. Whilst the iodine and protein
contents of the outermost layers were high, the alginic acid and ash
contents were low ; the iodine and protein quantitatively increased
from the transition region to the holdfast complex, whilst in the outer
*
A. D. BONEY
other parts of the plants, and similar results were obtained for the
mannitol, protein and fat contents. ,Evidence was also obtained of
changes in the metabolic rate with growth of the plant, and of different
concentration gradients with age.
The effects of depth of immersion on the chemical composition of
the Laminaria species common to Scotland have been reported by
Black (1960b). In general the variation in the fronds was far more
noticeable than that of the stipes. For Laminaria hyperborea the alginic
acid content showed little significant variation with depth in both stipe
and fronds, and whilst the stipes of L. digktata contained similar
quantities of alginic acid, the fronds had a tendency to show a somewhat
lower content with increasing depth during July, and some measurable
variation was also observed with L. saccharina. The mannitol reserves
were found to increase to depths of 6-10 my and then to decrease. By
contrast, the lamina& content fell progressively with depth. Where
any noticeable fluctuation occured in alginic acid the variation is
usually the inverse of mannitol, in keeping with Bidwell’s (1968)
observations. Differences of this nature are in part due to the degree of
sublittoral illumination, although other factors, probably associated
with available nutrients, are also involved. The most marked differences
were observed during the summer.
Black (1964a) studied concentration gradients in the fronds of
Laminaria sacchurina at Werent seasons. During the rapid growth
period (spring) little variation was observed in the composition of the
tissues along the frond. During the slow-growth period (August), and in
the autumn, considerable variation in chemical composition was
observed because of the variable age of the tissues. At the base of the
frond above the meristematic region, laminarin was absent, and proteins
and alginic acid were of very low value ; mannitol was present, and the
mineral content high. During the period of slow growth the upper twothirds of the lamina contains a reserve of laminarin and proteins, since
this is the period when continued photosynthesis and a reduction in the
rate of cell division leads to a steady accumulation of reserves. The
iodine and fucosterol contents were found to be at a maximum in the
transition region between stipe and frond. A study of chemical and
growth gradients was made also on Laminaria hyperborea (Black et al.,
1960). Lmsen and Haug (1961) investigated the biochemical gradients
in the stipe of Laminaria hyperborea, using the peripheral tissue, the
outer and inner cortex and the medulla. Whilst the iodine and protein
contents of the outermost layers were high, the alginic acid and ash
contents were low ; the iodine and protein quantitatively increased
from the transition region to the holdfast complex, whilst in the outer
*