We examined variations in lipid composition of the
marine green alga Ulva fenestrata grown under different
irradiance conditions (80% of incident photosynthetically
active radiation wPARx and 24% PAR). The ratio of storage
lipids (triacylglycerol) to major structural chloroplast
lipids (glycolipids and phosphatidylglycerol) was influenced
considerably by the irradiance. Triacylglycerol
predominated in U. fenestrata exposed to 80% PAR
(58.7"1.7% of total lipids). In contrast, when the alga
was grown at 24% PAR, the amount of monogalactosyldiacylglycerol,
sulfoquinovosyldiacylglycerol and
phosphatidylglycerol increased two to three and a half
times compared to algae cultivated at 80% PAR. The
content of digalactosyldiacylglycerol and betaine lipid in
U. fenestrata showed little dependence on light intensity.
Each lipid class had a characteristic fatty acid composition.
However, the relative proportions of fatty acids
present in triacylglycerol, monogalactosyldiacylglycerol
and sulfoquinovosyldiacylglycerol did not depend on irradiance
conditions. The variation in fatty acid composition
of digalactosyldiacylglycerol and phosphatidylglycerol
and changes in the amounts of lipids were responsible
for the differences in total fatty acid composition of U.
fenestrata among light intensities. The most sensitive to
the change in quantity of incident light were the 16:4n-3
and 16:0 acids. The highest level of 16:4n-3 acid was
detected in algae grown under 24% PAR, whereas 16:0
acid was highest at 80% PAR. However, the total lipid
content in the algae was relatively constant at different
light intensities (5.0"1.0 mg/g fresh weight at 80% PAR
and 5.2"1.1 mg/g at 24% PAR). These results suggest
that changes in lipid composition of U. fenestrata can be
considered as a mechanism of adaptation and survival
of thalli subjected to variations in solar irradiance.
We examined variations in lipid composition of themarine green alga Ulva fenestrata grown under differentirradiance conditions (80% of incident photosyntheticallyactive radiation wPARx and 24% PAR). The ratio of storagelipids (triacylglycerol) to major structural chloroplastlipids (glycolipids and phosphatidylglycerol) was influencedconsiderably by the irradiance. Triacylglycerolpredominated in U. fenestrata exposed to 80% PAR(58.7"1.7% of total lipids). In contrast, when the algawas grown at 24% PAR, the amount of monogalactosyldiacylglycerol,sulfoquinovosyldiacylglycerol andphosphatidylglycerol increased two to three and a halftimes compared to algae cultivated at 80% PAR. Thecontent of digalactosyldiacylglycerol and betaine lipid inU. fenestrata showed little dependence on light intensity.Each lipid class had a characteristic fatty acid composition.However, the relative proportions of fatty acidspresent in triacylglycerol, monogalactosyldiacylglyceroland sulfoquinovosyldiacylglycerol did not depend on irradianceconditions. The variation in fatty acid compositionof digalactosyldiacylglycerol and phosphatidylglyceroland changes in the amounts of lipids were responsiblefor the differences in total fatty acid composition of U.fenestrata among light intensities. The most sensitive tothe change in quantity of incident light were the 16:4n-3and 16:0 acids. The highest level of 16:4n-3 acid wasdetected in algae grown under 24% PAR, whereas 16:0acid was highest at 80% PAR. However, the total lipidcontent in the algae was relatively constant at differentlight intensities (5.0"1.0 mg/g fresh weight at 80% PARand 5.2"1.1 mg/g at 24% PAR). These results suggestthat changes in lipid composition of U. fenestrata can beconsidered as a mechanism of adaptation and survivalof thalli subjected to variations in solar irradiance.
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