Yoshiko Kashiwabara

Incorporation of14C-radioactivity into various lipid classes at different growth-stages of culturedLaminaria japonica

A study is reported on the incorporation of14C-acetate into lipid classes from three different growth stages ofLaminaria japonica, a species long used for food in Japan. This was done because of the possible utilization of its lipids.Radioactivity incorporated into whole lipids in the three growth stages under the same experimental conditions (10 °C, 500 lux) increased with maturity of the thalli. The radioactivity was found mainly in PC, TG and 1,2-DG and subsequently distributed into other lipid classes (PG,PI,PE,MGDG,SQDG and DGDG) to a lesser extent. The incorporation patterns of the former group were similar at all stages, but those of the latter group differed slightly according to growth stage.In juvenile thalli,14C was incorporated to a much higher extent into PG, MGDG, PI and fucosterol than PE, SQDG, DGDG and MG, while the14C-incorporation into MG, SQDG, DGDG and PS in the mature growth stage was higher than into the other lipid classes. The absolute level of incorporation was higher for all these compounds in mature thalli than the thalli of other growth stages.

Incorporation of 14C-radioactivity into lipid classes at different maturity of Laminaria japonica Aresch. cultured under natural and partially controlled conditions

A study to assess which environmental or developmental factors predominate in the biosynthesis of lipids of Laminaria japonica Aresch. blades was undertaken by means of 14C-labelling technique. In experiment 1, kelp blades at different growth stages were collected in different cultural seasons. In experiment 2, kelp blades of different sizes and maturity cultured simultaneously for two months in the same sea area were collected at the same time.The following results were obtained. In experiment 1, the 14C-incorporation into whole lipids was lowest in juvenile blades collected at the end of autumn and highest in blades of middle size collected in winter. However, the highest counts were incorporated in PC among complex lipid classes from all size classes of blades in both experiments 1 and 2. In experiment 2, 14C-incorporation patterns of individual lipid classes were characteristically different depending on the sizes of blades even under the same cultural condition. Thus, the biosynthesis of lipids in this kelp seems to be affected essentially by developmental factors.