Identification of spectral forms of protochlorophyllide in the region 670-730 nm.

Dark-grown leaves of three different species, maize, wheat, pea and a pea mutant (lip1) have been used to study protochlorophyllide (Pchlide) spectral forms. As a comparison also pea epicotyls were used. Different native forms of Pchlide were identified using the variation in the spectral properties of the plant material and the second derivatives of the 77 K fluorescence excitation and emission spectra. The spectral forms were further characterised by Gaussian deconvolution. In addition to short-wavelength and long-wavelength forms the area between 660 and 730 nm was shown to contain, together with some vibrational bands, five far-red Pchlide forms. They had pairs of excitation and emission peaks at 658 and 666 nm, 668 and 680 nm, 677 and 690 nm, 686 and 698 as well as 696 and 728 nm, respectively. The presence of several far-red Pchlide forms in dark-grown leaves gave evidence for additional aggregated states of Pchlide under native conditions.