Mn content changes in wheat etioplast membranes during greening under intermittent or continuous light

Abstract

Study of Mn content changes in wheat etioplasts during greening under intermittent or continuous light reveal an heterogeneity in the development of the chloroplast Mn pool. Under intermittent light plastids contain only the Tris extraction-resistant Mn pool. Such plastids are known to have no O 2 evolution capacity. The formation of the tightly bound Mn pool appears not to be a light-requiring process. But under intermittent light followed by 15 min continuous light plastids contain, like the control chloroplasts, two distinct Mn pools, the Tris extraction-resistant and the Tris-extracted pools. Such plastids are known to be capable of evolving O 2 in the presence of Hill reagents. The formation of the loosely bound Mn pool is a light-requiring process. Under continuous light, only the loosely bound Mn pool increases rapidly in the early stages of greening. These results suggest that protein complexes capable of Mn binding pre-exist in etioplasts and Mn atoms are light-inserted into the membrane complexes a as chlorophylls are synthesized.