Spectroscopic analysis of desiccation-induced alterations of the chlorophyllide transformation pathway in etiolated barley leaves

Effects of water deficit on the chlorophyllide (Chlide) transformation path way were studied in etiolated barley (Hordeum vulgare) leaves by analyzing absorption spectra and 77-K fluorescence spectra deconvoluted in components . Chlide transformations were examined in dehydrated leaves exposed to a 35 -ms saturating flash triggering protochlorophyllide (Pchlide) and Chlide tr ansformation processes. During the 90 min following the flash, we found tha t dehydration induced modifications of Chlide transformations, but no effec t on Pchlide phototransformation into Chlide was observed. During this time , content of NADPH-Pchlide oxydoreductase in leaves did not change. Chlide transformation process in dehydrated leaves was characterized by the altera tion of the Shibata shift process, by the appearance of a new Chlide specie s emitting at 692 run, and by the favored formation of Chl(ide) A(668)F(676 ). The formation of Chl(ide) A(668)F(676), so-called "free Chlide," was pro bably induced by disaggregation of highly aggregated Chlide complexes. Here , we offer evidence for the alteration of photoactive Pchlide regeneration process, which may be caused by the desiccation-induced inhibition of Pchli de synthesis.