Absence of phytochrome participation in chlorophyll synthesis in euglena.

There appear to be three phases in chlorophyll synthesis in Euglena (11). An initial, rapid conversion of a small pool of protochlorophyll(ide) to chlorophyll is followed by a short lag phase during which the protochlorophyll(ide) pool is replenished; the third phase is that of rapid and sustained chlorophyll synthesis. Since the initial pool of protochlorophyll(ide) is smaller than would be expected from an intermediate accumulating behind a dark-blocked step (11), Gassman and Bogorad (5) suggested that in vascular plants the concentration of its precursor, 8-amino levulinic acid, may be limiting, but there is no proof that ALA2 is limiting in Euglena. In higher plants, many workers (2, 4, 12) found that the enzymatic synbefore being used for an experiment (3). Although Dr. Carl A. Price (personal communication) found that ALA may not penetrate into Euglena cells, ALA was added to a final concentration of 1 ptM to decrease the possibility that ALA might be limiting chlorophyll synthesis. Cell counts were made with a Sedgwick-Rafter plankton counter (8) after killing the cells with 1.5% (v/v) formaldehyde. Chlorophyll was determined by the method of Arnon (1) after extraction into 80% (v/v) acetone and filtration through glass fiber filter disks. Results are expressed as mg total chlorophyll/ cell. Red light (peak at 660 nm, 1270 Mw/cm2) and far red light (peak at 720-730 nm, 1590 Miw/cm2) were obtained with solid