ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
The phototransformation of protochlorophyllide forms was studied in epicotyls of dark-germinated pea (Pisum sativum L. cv. Zsuzsi) seedlings. Middle segments were illuminated with white or 632.8 nm laser flash or continuous light at room temperature and at −15°C. At low light intensities, photoreduction could be distinguished from bleaching. 77 K fluorescence emission spectra were measured, difference spectra of illuminated and non-illuminated samples were calculated and/or the spectra were deconvoluted into Gaussian components. The 629 nm-emitting protochlorophyllide form, P629 (Pxxx where xxx is the fluorescence emission maximum), was inactive. For short-period (2–100 ms) and/or low-intensity (0.75–1.5 µmol m−2 s−1) illumination, particularly with laser light, the transformation of P636 into the 678 nm-emitting chlorophyllide form, C678 (Cxxx where xxx is the fluorescence emission maximum), was characteristic. This process was also found when the samples were cooled to −15°C. The transformation of P644 into C684 usually proceeded in parallel with the process above as a result of the strong overlap of the excitation bands of P636 and P644. The Shibata shift of C684 into a short-wavelength form, C675–676, was observed. Long-period (20–600 s) and/or high-intensity (above 10 µmol m−2 s−1) illumination resulted in the parallel transformation of P655 into C692. These results demonstrate that three flash-photoactive protochlorophyllide forms function in pea epicotyls. As a part of P636 is flash photoactive, its protochlorophyllide molecule must be bound to the active site of a monomer protein unit [Böddi B, Kis-Petik K, Kaposi AD, Fidy J, Sundqvist C (1998) The two short wavelength protochlorophyllide forms in pea epicotyls are both monomeric. Biochim Biophys Acta 1365: 531–540] of the NADPH:protochlorophyllide oxidoreductase (EC 1.3.1.33). Dynamic interconversions of the protochlorophyllide forms into each other, and their regeneration, were also found, which are summarized in a scheme.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.2005.00487.x
