BIOLOGY OF SEAWEEDS OF ECONOMIC IMPORTANCE
203
variation in the stipes. Laminarin was absent in the late winter and
early spring, as with the other species, and reached its peak value in
July and August. The mannitol content of the fronds showed summer
and autumn peaks similar to that of L. digitata, and the protein contents
were highest in the spring and low in early autumn. As noted earlier,
growth of Laminuria plants was most rapid in the first 6 months of the
year, and the older tissues on the distal end of the frondage was continuously worn away. I n general, when the rapid growth phase commenced the protein content was high and thereafter fell steadily. By
contrast, laminarin was present in negligible quantities and the mannitol values were low at this time. Both compounds reached peak
values at similar times. Whilst the rate of growth decreased in the
summer the mannitol and laminarin accumulated because of continued
assimilation, and with the increased protein content of the autumn
months there was an accompanying fall in the laminarin and mannitol.
The times when the alginic acid contents were high roughly correspond
with the peak values for protein. Seasonal fluctuations were also
observed in the mineral salt content and total dry weights of the plants.
Differences due to environmental factors have also been observed in
addition to the seasonal variations.
The seasonal variation in the biochemical composition of species of
Laminaria and Alaria esculenta in Norway has been described by
Haug and Jensen (1954). I n general the results were similar to those
obtained by Black (p. 201). The fronds of Laminaria plants showed
alginic acid maxima in spring and minima in the autumn, whilst with
Alaria the highest yields were observed in March and lowest in autumn.
The stipe contents fluctuated very little. Mannitol contents were at a
maximum from June to November, but were very low from February
to May, and the laminarin contents showed extreme variations, being
absent from February to June, then rising to a maximum in autumn
before falling again. The alginic acid content of Alaria esculenta showed
a seasonal fluctuation similar to that of Laminaria, and in both genera
the protein contents followed a similar course to that of alginic acid.
Laminaria plants have been analysed in Japan (Suzuki, 1955).
Mannitol was at a minimal value in spring, and then increased throughout the summer. The protein and fat contents were at a maximum in
spring and a minimum in the autumn. The seasonal variation of alginic
acid appeared not to be so readily distinguishable. Seasonal analyses of
Alaria crassifolia and Undaria pinnatifida f. distans have also been
reported (Togasawa, 1954; Togasawa and Mino, 1954; Takagi and
Murata, 1955). Analysis of carbohydrates showed that the reducing
sugar content of the sporophylls was appreciably higher than that of
203
variation in the stipes. Laminarin was absent in the late winter and
early spring, as with the other species, and reached its peak value in
July and August. The mannitol content of the fronds showed summer
and autumn peaks similar to that of L. digitata, and the protein contents
were highest in the spring and low in early autumn. As noted earlier,
growth of Laminuria plants was most rapid in the first 6 months of the
year, and the older tissues on the distal end of the frondage was continuously worn away. I n general, when the rapid growth phase commenced the protein content was high and thereafter fell steadily. By
contrast, laminarin was present in negligible quantities and the mannitol values were low at this time. Both compounds reached peak
values at similar times. Whilst the rate of growth decreased in the
summer the mannitol and laminarin accumulated because of continued
assimilation, and with the increased protein content of the autumn
months there was an accompanying fall in the laminarin and mannitol.
The times when the alginic acid contents were high roughly correspond
with the peak values for protein. Seasonal fluctuations were also
observed in the mineral salt content and total dry weights of the plants.
Differences due to environmental factors have also been observed in
addition to the seasonal variations.
The seasonal variation in the biochemical composition of species of
Laminaria and Alaria esculenta in Norway has been described by
Haug and Jensen (1954). I n general the results were similar to those
obtained by Black (p. 201). The fronds of Laminaria plants showed
alginic acid maxima in spring and minima in the autumn, whilst with
Alaria the highest yields were observed in March and lowest in autumn.
The stipe contents fluctuated very little. Mannitol contents were at a
maximum from June to November, but were very low from February
to May, and the laminarin contents showed extreme variations, being
absent from February to June, then rising to a maximum in autumn
before falling again. The alginic acid content of Alaria esculenta showed
a seasonal fluctuation similar to that of Laminaria, and in both genera
the protein contents followed a similar course to that of alginic acid.
Laminaria plants have been analysed in Japan (Suzuki, 1955).
Mannitol was at a minimal value in spring, and then increased throughout the summer. The protein and fat contents were at a maximum in
spring and a minimum in the autumn. The seasonal variation of alginic
acid appeared not to be so readily distinguishable. Seasonal analyses of
Alaria crassifolia and Undaria pinnatifida f. distans have also been
reported (Togasawa, 1954; Togasawa and Mino, 1954; Takagi and
Murata, 1955). Analysis of carbohydrates showed that the reducing
sugar content of the sporophylls was appreciably higher than that of