A FULLY AUTOMATED DUAL-WAVELENGTH PHOTOMETER FOR PHYTOCHROME MEASUREMENTS AND ITS APPLICATION TO PHYTOCHROME FROM CHLOROPHYLL-CONTAINING EXTRACTS

The photometer described here measures phytochrome photoreversibility of as many as 20 samples fully automatically. Monochromatic light of t wo laser diodes (670 and 780 nm) is used as a source for the measuring light beam. The whole measuring procedure is controlled by a computer linked to a lock-in amplifier. This arrangement permits a rather simp le construction and allows automatic zeroing and sample change. In add ition the application of a Triton phase partitioning method to allow p hytochrome photoreversibility measurements of extracts of green tissue is described. A single phase partitioning with a chlorophyll/phytochr ome mixture reduced chlorophyll concentration to less than 10%. Repeat ed phase partitioning of crude extracts from green moss protonemata re duced chlorophyll content to less than 2% while leaving the phytochrom e concentration almost unchanged. In some instances this method has ad vantages over polyethyleneimine precipitation, which is commonly used to obtain chlorophyll-free extracts.