QUANTITATIVE VIABILITY OF SEAWEED TISSUES ASSESSED WITH 2,3,5-TRIPHENYLTETRAZOLIUM CHLORIDE

A spectrophotometric quantification method was optimized to evaluate i ts utility in seaweed tissue viability tests using the enzymatic reduc tion of colorless 2,3,5-triphenyltetrazolium chloride (TTC) to a color ed triphenylformazan (TPF). To allow accurate determination of TPF in the seaweed Porphyra thallus and conchocelis, 0.2 g of tissues are inc ubated with 4 mL of 0.8% TTC reagent in the dark at 20 degrees C for 1 h under a mineral oil layer. The TPF formed in tissues was extracted for 15 min at 60 degrees C with 2 mL of 0.2 N KOH in 25% ethanol. Then TPF is partitioned away by prompt addition of hexane and vortexing. B y this procedure, we have observed nearly complete separation of TPF, and observed good spectrophotometric discrimination between TPF and ot her hexane-soluble pigments at 545 nm. This procedure has proved appli cable to a wide range of seaweed taxa; 1 species of Chlorophyta, 4 spe cies of Phaeophyta and 7 species of Rhodophyta tested.