2.5. Estimation of the photosynthetic pigments
The photosynthetic pigments i.e. chlorophyll a (Chl a ) and
carotenoids (Car), in each culture of Anabaena PCC 7120 was
extracted following the methods of Porra et al. (1989) and Goodwin
(1954), thereby recording the absorbance spectrophotometrically
(Systronics, India) at 665 nm and 450 nm, respectively. The contents of
phycobiliproteins i.e. allophycocyanin (APC), phycocyanin (PC) and
phycoerythrin (PE) were determined spectrophotometrically by recording
the absorbance of the supernatant at 652, 615 and 562 nm, respectively
following the method of Bennett and Bogorad (1973). Following equation
was used to determine the phycobiliproteins content (μg
mg−1 dry weight):
APC = A652 – 0.208 (A615)/5.09
PC = A615 – (0.474 * A652)/ 5.34
PE = A562 * 2.41 (PC) – 0.849 (APC)/9.62