EFFECT OF IRRADIANCE AND LIGHT QUALITY ON STARCH SYNTHESIS BY ISOLATED CHLOROPLASTS OF CODIUM FRAGILE

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Summary

Net starch synthesis by isolated chloroplasts of the intertidal alga Codium fragile (Suringar) Hariot was determined by enzymic hydrolysis (amyloglucosidase/α-amylase) of solubilized chloroplast samples followed by the measurement of the resultant glucose yields by hexokinase/glucose-6-phosphate dehydrogenase-coupled reactions.

Net starch synthesis was only observed between 100 and 375 μmol m−2 s−1 (PAR) corresponding to irradiance values which supported saturating or super-saturating rates of photosynthesis. Light filter inactivation of the light-harvesting complex carotenoids siphonoxanthin and siphonein reduced net starch synthesis by 68 %. These findings are discussed in relation to photosynthesis in an intertidal zone environment.

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