Chlorophyll interference with phytochrome measurement

Measurements of phytochrome by (A_{725–815 nm}) were completely suppressed at chlorophyll concentrations of the order of 20–40 g g^-1 f.wt. in vivo and 37 g cm^-3 in vitro, and the readings were reduced by 50% at only 12 g cm^-3 in vitro. At these concentrations of chlorophyll in aqueous methanol, the loss of phytochrome signal in vitro appeared to be due to failure of phytochrome photoconversion rather than to interference with A measuremebt by chlorophyll fluorescence in the 125/815 nm measuring beam.Abbreviations Chl chlorophyll - P phytochrome - P_r and P_fr phytochrome in red absorbing and far-red absorbing forms