The two spectroscopically different short wavelength protochlorophyllide forms in pea epicotyls are both monomeric

Abstract

The spectral properties of the protochlorophyllide forms in the epicotyls of dark-grown pea seedlings have been studied in a temperature range, from 10 to 293 K with conventional fluorescence emission and excitation spectroscopy as well as by fluorescence line narrowing (FLN) at cryogenic temperatures. The conventional fluorescence techniques at lower temperatures revealed separate bands at 628, 634-636, 644 and 655 nm. At room temperature (293 K) the 628 and 634-636 nm emission bands strongly overlapped and the band shape was almost independent of the excitation wavelength. Under FLN conditions, vibronically resolved fluorescence spectra could be measured for the 628 and 634-636 nm bands. The high resolution of this technique excluded the excitonic nature of respective excited states and made it possible to determine the pure electronic (0,0) range of the spectra of the two components. Thus it was concluded that the 628 and 634-636 nm (0,0) emission bands originate from two monomeric forms of protochlorophyllide and the spectral difference is interpreted as a consequence of environmental effects of the surrounding matrix. On the basis of earlier results and the data presented here, a model is discussed in which the 636 nm form is considered as an enzyme-bound protochlorophyllide and the 628 nm form as a protochlorophyllide pool from which the substrate is replaced when the epicotyl is illuminated with continuous light.

Three-Dimensional Visualization of the Tubular-Lamellar Transformation of the Internal Plastid Membrane Network during Runner Bean Chloroplast Biogenesis

“…These two Pchlide forms are photoconvertible. An analysis of low-temperature fluorescence (77K) spectra has revealed one more type of Pchlide: the nonphotoconvertible form Pchlide 628-633 (Böddi et al, 1998). The longer wavelength forms are bound to PLBs, while this shorter wavelength form, unbound to LPOR, is mainly found in PTs.…”

Tissue specific protochlorophyll(ide) forms in dark-forced shoots of grapevine (Vitis viniferaL.)

“…When the 595 nm excitation was used, the 654.5 nm band became the maximum of the spectrum and the short-wavelength band showed a complex structure with shoulders around 630 and 640 nm and a local maximum at 635 nm ( Figure 5). However, we could not find an excitation wavelength, which could separately excite the 644 nm emission band reported in the 10 K emission spectra of pea epicotyls (Bo¨ddi et al 1998). The existence of this band was shown only by the complexity of the shorter wavelength band in the spectrum measured with 595 nm excitation ( Figure 5).…”

“…These absorption bands are usual in spectra of porphyrins and are present also in spectra of pea epicotyls (Bo¨ddi et al 1998). With 575 nm excitation, the main emission band appeared at 629 nm.…”

“…This band was not found in the 77 K spectra of the pea epicotyl. It was detected only as a small Gaussian component in the 10 K spectra (Bo¨ddi et al 1998) but is generally present as an overlapped Gaussian component in 77 K spectra of leaves of etiolated seedlings (Bo¨ddi et al 1992). It is worth mentioning that the appearance of this band did not depend on the age of the stem.…”

Red region excitation spectra of protochlorophyllide in dark-grown leaves from plant species with different proportions of its spectral forms

“…in Arabidopsis), as three differently regulated isoforms: PORA, PORB, and PORC (Su et al 2001). Nonphotoactive Pchlide is considered not to bind directly to the active site of the photo-enzyme, and be present mostly in monomeric forms (Böddi et al 1998). Aggregated forms having NADP + instead of NADPH also lack photoactivity (Schoefs et al 2000).…”