Protochlorophyllide spectral forms.

Abstract: This study summarized recent results on POR and plastid development in order to find an explanation for the existence of Pchlide spectral forms. This review has summarized many researches about the Pchlide spectral forms and their phototransformability in different higher plants which have been published. Chlorophyll (Chl) is the most important pigment on the Earth. Each spring millions of tons Chl are formed during bud break and leaf development. The sun light needed for photosynthesis is captured by Chl and transformed to chemical energy. In the Biosynthesis of chlorophyll (Chl) begins with the synthesis of delta-aminolevulinic acid (ALA) from glutamic acid. Chl biosynthetic pathway, a light dependent enzyme protochlorophyllide oxidoreductase (POR) catalyses a key light-driven reaction, trans addition of hydrogen across the C-17-C-18 double bond of the Chl precursor, protochlorophyllide (Pchlide), that triggers a profound transformation in plant development. Pchlide is spectrally heterogeneous and exist in different spectral forms having slightly different absorption and fluorescence peaks. The identified Pchlide spectral forms can be sorted into three groups. The first group is designated as short-wavelength forms. This group with fluorescence in the 625-646 nm spectral region has a heterogeneous nature and is made by four components. The second group includes the long-wavelength Pchlide forms with emission maxima between 652 and 657 nm. The third group is found in the extreme red region (670-730 nm) of the fluorescence emission spectra and includes a number of pigment forms with spectral bands of low intensity. This region is also influenced by vibrational bands of the short-and long-wavelength Pchlide forms.