Protochlorophyllide and POR development in dark‐grown plants with different proportions of short‐wavelength and long‐wavelength protochlorophyllide spectral forms^†

Abstract

The effect of leaf developmental age on the protochlorophyllide (Pchlide) spectral forms and the expression of messenger RNA (mRNA) encoding NADPH-protochlorophyllide oxidoreductase (POR) were investigated. Four plant species, maize, wheat, pea and the lip1 mutant of pea, known to have different composition of the spectral forms of Pchlide, were used. In very young plants short-wavelength Pchlide with a fluorescence emission at 631 nm was dominating. Long-wavelength Pchlide fluorescing mainly around 655 nm increased during development, which led to a relative decrease of the shortwavelength forms. During ageing of the leaves, the short-wavelength forms slightly increased again. The different proportions of short-and longwavelength Pchlide spectral forms were, however, found to vary with the developmental stage in a species specific pattern. The steady-state level of POR mRNA and the amount of the POR protein were similar in species dominated by short-wavelength forms and in species dominated with longwavelength forms. Even if POR is necessary for the formation of the longwavelength Pchlide form it is not the only limiting factor for formation of long-wavelength Pchlide forms in mature plants.

Prolonged salt stress alters the ratios of protochlorophyllide spectral forms in dark-grown wheat (Triticum aestivum) and influences chlorophyll a accumulation following irradiation

“…During development, the Pchlide content of the leaf increases and the proportions of the different spectral forms change (He et al 1994;Amirjani et al 2006). Since salt stress affects the growth of the leaf, we hypothesized that it might also influence the accumulation of Pchlide and formation of different Pchlide spectral forms.…”