REGULAR PAPER Dominance of a 675 nm chlorophyll(ide) form upon selective 632.8 or 654 nm laser illumination after partial protochlorophyllide phototransformation Annama ´ria Ko ´sa • Be ´la Bo ¨ddi Received: 13 March 2012 / Accepted: 18 October 2012 Ó Springer Science+Business Media Dordrecht 2012 Abstract The phototransformation pathways of proto- chlorophyllide forms were studied in 8–14-day-old leaves of dark-germinated wheat (Triticum aestivum L.) using white, 632.8 nm He–Ne laser and 654 nm laser diode light. The photon flux density (PFD) values (0.75–360 lmol photons m -2 s -1 ), the illumination periods (20 ms–10 s) and the temperature of the leaves (between -60 °C and room temperature) were varied. The 77 K fluorescence spectra of partially phototransformed leaves showed grad- ual accumulation or even the dominance of the 675 nm emitting chlorophyllide or chlorophyll form at room tem- perature with 632.8 nm of PFD less than 200 lmol pho- tons m -2 s -1 or with 654 nm of low PFD (7.5 lmol photons m -2 s -1 ) up to 1 s. Longer wavelength (685 or 690 nm) emitting chlorophyllide forms appeared at illu- minations under -25 °C with both laser lights or at room temperature when the PFD values were higher or the illu- mination period was longer than above. We concluded that the formation of the 675 nm emitting chlorophyllide form does not indicate the direct photoactivity of the 633 nm emitting protochlorophyllide form; it can derive from 644 and 657 nm forms via instantaneous disaggregation of the newly-produced chlorophyllide complexes. The disaggre- gation is strongly influenced by the molecular environment and the localization of the complex. Keywords Chlorophyllide form Á Etiolated wheat Á Laser illumination Á Protochlorophyllide phototransformation Á 77 K fluorescence emission Abbreviations Chlide Chlorophyllide Cxxx Chlorophyllide form with fluorescence emission maximum at xxx nm Pchlide Protochlorophyllide PFD Photon flux density PLB Prolamellar body POR NADPH:Pchlide oxidoreductase PT Prothylakoid Pxxx Protochlorophyllide form with fluorescence emission maximum at xxx nm ROS Reactive oxygen species Introduction Numerous data are available on the greening process of etiolated angiosperm leaves, particularly on protochloro- phyllide (Pchlide) reduction (Amirjani 2010; Belyaeva and Litvin 2011; Reinbothe et al. 2010); however, the exact role of the different Pchlide complexes in the formation of various chlorophyllide (Chlide) complexes is still disputed. A variety of phototransformation schemes has been published (Belyaeva and Litvin 2009). The early models were linear, indicated only the main pathway, i.e., the fast photoreduction of the major, 650 nm absorbing Pchlide complex (Shibata 1957), which emits fluorescence at 657 nm (P657). This complex is an oligomer of the NADPH: Pchlide oxidoreductase enzyme (POR, EC 1.3.1.33) units (Bo ¨ddi et al. 1989; Wiktorsson et al. 1993). These units are ternary complexes of POR–Pchlide– NADPH (Griffiths 1978). Besides this oligomer, a dimer photoactive complex with 645 nm emission maximum (P645) has been described (Martin et al. 1997; Mathis and Sauer 1972; Ouazzani Chahdi et al. 1998). Both the A. Ko ´sa Á B. Bo ¨ddi (&) Department of Plant Anatomy, Institute of Biology, Eo ¨tvo ¨s University, Pa ´zma ´ny P. s. 1/c, Budapest 1117, Hungary e-mail: bela.boddi@gmail.com 123 Photosynth Res DOI 10.1007/s11120-012-9782-1