Plant Physiol, September 2001, Vol. 127, pp. 202-211

Spectroscopic Analysis of Desiccation-Induced Alterations of the Chlorophyllide Transformation Pathway in Etiolated Barley Leaves¹

Department of Chemistry, Centre de Recherche en Toxicologie de l'Environnement, University of Quebec, Succursale Centre Ville, Case Postale 8888, Montreal, Quebec, Canada H3C 3P8 (P.L., D.K., P.J., D.D., R.P.); and Department of Plant Anatomy, Eötvös University, Puskin Street 11-13, Budapest, H-1088, Hungary (B.B.)

Effects of water deficit on the chlorophyllide (Chlide) transformation pathway 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 transformation processes. During the 90 min following the flash, we found that dehydration induced modifications of Chlide transformations, but no effect 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 alteration of the Shibata shift process, by the appearance of a new Chlide species emitting at 692 nm, and by the favored formation of Chl(ide) A₆₆₈F₆₇₆. The formation of Chl(ide) A₆₆₈F₆₇₆, so-called "free Chlide," was probably 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 Pchlide synthesis.