The Pool Size of Protochlorophyllide during Different Stages of Greening of Dark Grown Wheat Leaves

Abstract

The pool size of protochlorophyllide in wheat leaves irradiated for 5 minutes to 6 hours was studied. Protochlorophyllide then accumulated in the dark, but the pool size of regenerated protochlorophyllide was considerably smaller in leaves irradiated for six hours than in leaves irradiated for 5 minutes. The decrease in pool size of regenerated protochlorophyllide was found to take place at the time when the chlorophyll formation had accelerated and reached the linear phase. The protochlorophyllide accumulated is the form with absorption maximum at 650 nm, which is phototransformed to chlorophyllide with maximum absorption at 684 nm. This species goes through the Shibata shift when formed even after 6 hours of irradiation. If leaves, irradiated for 1 or 6 hours, were fed with δ‐amino‐levulinic acid the protochlorophyllide synthesis was only 1.2 times faster in the leaves irradiated for 6 hours than in those irradiated for 1 hour. In the case of leaves fed with δ‐amino‐levulinic acid the absorption maximum of protochlorophyllide is at 636 nm and the absorption maximum of the chlorophyllide formed is at 672 nm.

Light modulation of the activity of protochlorophyllide reductase

“…3) correlates with the rate of protochlorophyllide resynthesis (Mapleston, 1978;Augustinussen & Madsen, 1965). Also, the extent of protochlorophyllide resynthesis after different times of illumination (Mapleston, 1978;Sundqvist, 1974) is strictly paralleled by the differing extents of reactivation of the reductase under similar conditions (Fig. 4).…”

Two NADPH:Protochlorophyllide Oxidoreductases in Barley: Evidence for the Selective Disappearance of PORA during the Light-Induced Greening of Etiolated Seedlings.

“…When etiolated barley seedlings are exposed to light, both the decline of porA mRNA (Apel, 1981;Batschauer and Apel, 1984;Mosinger et al, 1985;Holtorf et al, 1995) and the reduction of Pchlide concentration (Sundqvist, 1974;Griffiths et al, 1985), which impairs the uptake of the precursor enzyme into the plastids (Reinbotheetal., 1995a(Reinbotheetal., , 1995b, should lead to a drastic reduction in the amount of the mature PORA in the developing chloroplasts. However, small amounts of PORA might persist and could remain active in the greening plants if the enzyme protein were not proteolytically degraded.…”

The Protochlorophyllide Holochrome of Barley (Hordeum vulgare L.)

“…In this case the rate of chlorophyll formation during the illumination would be limited by factors other than the amount of enzyme protein. There is evidence that shortly after the beginning of the light treatment protochlorophyllide as well as NADPH may become rate-limiting for the synthesis of chlorophyll : the concentration of the two substrates is rapidly decreased and remains at a low level during the subsequent illumination [21,23,24]. When the illuminated plants are returned to darkness the level of the two substrates increases again [21,23,24] and, at the same time, the enzyme protein is transformed into a photoactive complex which is susceptible to a light-induced breakdown (Fig.…”