Stability of Isolated Chloroplast Preparations and its Effect on Hill Reaction Measurements.

Since the time of the discovery and the first characterization of the Hill reaction (13, 14) there have been many subsequent studies of this process. As might have been expected, the results obtained in these different studies are rather contradictory, so much so that it is not clear what the characteristics of the Hill reaction are. This point is well illustrated in the complete review of the older Hill reaction work found in Rabinowitch (30). From a preliminary consideration of this problem (26) it seemed possible that the contradictions in the literature were due to the use of intact chloroplasts by some workers and fragmented chloroplasts by others. The results obtained in this study have made it clear, however, that the observed properties of a chloroplast preparation are strongly influenced by a number of factors such as the stability of the material, the species plant from which the chloroplasts were isolated and its physiological condition, and the time needed to make a measurement, to name but a few. Additional complications have been introduced by the recent finding that phosphorylation can be an integral part of the Hill reaction (2). The purpose of this paper is to fit together the pieces of this puzzle, insofar as possible, and show that one description of the Hill reaction will suffice to explain the results obtained in different studies.