During the illumination of etiolated barley plants a rapid decline of the NADPH : protochlorophyllide oxidoreductase is observed. Within the first 5 min of continuous light approximately 90% of the enzyme activity present in dark-grown barley plants disappears and, at the same time, the amount of enzyme protein is diminished by more than 60%. No stable polypeptide fragments have been found which might be formed during the lightinduced degradation of the enzyme protein. The rate of enzyme protein synthesis is not drastically affected at the beginning of the illumination period. During the subsequent light-dependent chloroplast development a phytochrome-induced decline in the rate of protein synthesis, concomittant with a continuous light-dependent degradation of the enzyme protein, leads to a progressive decrease of the concentration of the enzyme. After 6 h of continuous light, when the rate of chlorophyll accumulation is at its greatest, only traces of the enzyme protein are visible and the enzyme activity is no longer detectable within the plants. In contrast to previous concepts of chlorophyll biosynthesis in higher plants, our results present evidence that the NADPH : protochlorophyllide oxidoreductase functions only for a short time period after the onset of light.

Sensor technologies are expedient tools for precision agriculture, aiming for yield protection while reducing operating costs. A portable sensor based on chlorophyll fluorescence imaging was used in greenhouse experiments to investigate the response of sugar beet and soybean cultivars to the application of herbicides. The sensor measured the maximum quantum efficacy yield in photosystem II (PS-II) (Fv/Fm). In sugar beet, the averageFv/Fmof 9 different cultivars 1 d after treatment of desmedipham plus phenmedipham plus ethofumesate plus lenacil was reduced by 56% compared to the nontreated control. In soybean, the application of metribuzin plus clomazone reducedFv/Fmby 35% 9 d after application in 7 different cultivars. Sugar beets recovered within few days from herbicide stress while maximum quantum efficacy yield in PS-II of soybean cultivars was reduced up to 28 d. At the end of the experiment, approximately 30 d after treatment, biomass was reduced up to 77% in sugar beet and 92% in soybean. Chlorophyll fluorescence imaging is a useful diagnostic tool to quantify phytotoxicity of herbicides on crop cultivars directly after herbicide application, but does not correlate with biomass reduction.

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The NADPH:protochlorophyllide oxidoreductase of barley has been solubilized from etioplast membranes and purified to apparent homogeneity. The highest specific activity measured for the purified enzyme was 1.6 nmol chlorophyllide formed (mg protein−1) per flash. Electrophoretic analysis of the purified enzyme on sodium dodecylsulfate/polyacrylamide gels revealed only, one polypeptide of Mr 36000. During glycerol gradient centrifugation the enzyme migrates as a low‐molecular‐weight component. It is proposed that each enzyme molecule contains only one polypeptide chain. Assuming a molecular weight of 36000 for the enzyme, it was calculated that two or three protochlorophyllide molecules are bound to each enzyme molecule.

The antibiotic vulgamycin was isolated from a new strain of Streptomyces. Vulgamycin shows herbicidal activity when applied post‐emergence. It controls dicotyledonous weeds and grasses such as Setaria sp. at dosages between 125 and 500 g ha−1. Crops such as cotton, barley and maize tolerate vulgamycin very well. Biochemical mode‐of‐action studies indicate some effect of vulgamycin on an isoleucine‐dependent step within the cell cycle, so‐called GI‐arrest.