Replacement of photosynthetic electron transport inhibitors by silicomolybdate

KCN-treated spinach chloroplasts, their photosystem I being ineffective, exhibit a single reaction site for silicomolybdate. Using this heteropolyanion as electron acceptor, photosynthetic oxygen evolution is partially inhibited by ureas, triazines, or phenylpyridazinone herbicides, their inhibitory effect depending on the concentration of silicomolybate. Labelled atrazine attached to isolated chloroplast material is competitively replaced by silicomolybdate in the same manner as e.g. ureas complete with a triazine herbicide. – It is concluded (1) that silicomolybdate is bound and reduced at the herbicide-binding protein, and (2) that the inhibition of silicomolybdate reduction by herbicides such as DCMU is due to loss of reaction sites for silicomolybdate.     

Bryonoside and bryoside—new triterpene glycosides from Bryonia dioica

The structures of two new triterpene glycosides from Bryonia dioica have been shown, on the basis of chemical and FDMS and ¹H and ¹³C NMR s     

Inhibition by light of growth and Golgi-localized glucan synthetase in the maize mesocotyl

When dark-grown maize (Zea mays L.) seedlings were exposed to red light (R), Golgi-localized glucan synthetase activity in the mesocotyl began to decrease within 1 h, and fell by approx. 70% in 12 h. The response required at least 10^-2 mol m^-2 R and saturated at 100 mol m^-2. Far-red light (FR) alone inhibited glucan synthetase, and FR reversed the inhibition by R back to the level caused by FR alone. Density gradient fractionation indicated that of the major membrane markers only the Golgi-localized glucan-synthetase activity was affected by R. Golgi-localized latent inosine-diphosphatase activity was unaffected. The kinetics of the response, the photon fluence dependence, and the reversibility by FR all correlated with the inhibition by light of elongation of the mesocotyl, indicating that light inhibits growth and glucan synthetase activity by a similar mechanism.Abbreviations FR far-red light - GS glucan synthetase - IAA indole-3-acetic acid - R red light     

The endogenous gibberellins of vegetative and reproductive tissue of G2 peas

The gibberellins (GAs) of both vegetative (leaves and stems) and reproductive (pods and seeds) tissue of the G2 strain of peas Pisum sativum L. were characterized in purified extracts by a combination of sequential silicic-acid partition column chromatography, and gas chromatography-mass spectrometry. Gibberellins A₁₉, A₂₀, A₂₉ and an A₂₉ catabolite were identified in both types of tissue. Gibberellins A₉, A₁₇ and A₄₄ were also found in pods and seeds.Abbreviations FID Ilame ionization detector - GA(s) gibberellin(s) - GC gas chromatograph(y) - HPLC high performance liquid chromatograph(y) - LD long day - MS mass spectrum(a) or mass spectrometer(ry) - SD short day     

The site of carotenogenic enzymes in chromoplasts from Narcissus pseudonarcissus L.

The membranes from the chromoplasts of Narcissus pseudonarcissus L. which are derived from the inner envelope membrane are the site of -carotene synthesis from [1-¹⁴C]isopentenyl diphosphate. The enzymes involved are partly peripheral membrane proteins (prenyltransferase, phytoene synthase) and partly integral membrane proteins (cis-trans isomerase, dehydrogenase(s), cyclase(s)). Metabolic channeling is suggested.Abbreviations IPP isopentenyl diphosphate - GGPP geranylgeranyl diphosphate     

An automatic method for determination of urinary 3-methylhistidine: normal values.

A system for automatic analysis of urinary 3-methylhistidine is described, applying ion-exchange chromatography and using an automatic sample injector, a motoric selector valve, and a diode programmer, which controls the analytical system. The method permits a sampling rate of 22 samples/day. 3-Methylhistidine was completely separated from histidine in 37 min whereas 1-methylhistidine was eluted together with ammonia. The 3-methylhistidine concentration was linear up to 150 nmol/ml and no appreciable sample interaction was found at automatic sequential runs. The error, in a single determination based on duplicate samples, was 4.61% and, in duplicated determinations, 3.26%. The mean urinary 3-methylhistidine output was 299.4 ± 23.8 μmol/day in 12 healthy females and 545.5 ± 35.2 μmol/day in 12 healthy males. The 3-methylhistidine excretion was significantly higher in males than in females, when expressed as the absolute daily output or as the estimated ratio to body weight, body surface area, or creatinine.     

The modulation of membrane fluidity by hydrogenation processes. III. The hydrogenation of biomembranes of spinach chloroplasts and a study of the effect of this on photosynthetic electron transport

A method is reported for the in situ modification of the lipids of isolated spinach chloroplast membranes. The technique is based on a direct hydrogenation of the lipid double bonds in the presence of the catalyst, chlorotris(triphenylphosphine)rhodium (I). The pattern of hydrogenation achieved suggests that the catalyst distributes amongst all of the membranes. The polyunsaturated lipids within the membranes are hydrogenated at a faster rate and at an earlier stage than are the monoenoic lipids.Whilst addition of the catalyst to the chloroplast causes an initial 10–20% decrease in Hill activity, saturation of up to 40% of the double bonds present can be accomplished without causing further significant alterations in photosynthetic electron transport processes or marked morphological changes of the chloroplast structure as observed in the electron microscope.     

β-Carotene synthesis in isolated chromoplasts from Narcissus pseudonarcissus

A system has been established from isolated intact chromoplasts of Narcissus pseudonarcissus flowers that synthesizes geranylgeraniol, an unknown polyprenoid alcohol, phytoene, and -carotene from [1-¹⁴C]isopentenyl pyrophosphate in a good yeild. Long chain pyrophosphates are not accumulated. San 6706 inhibits the dehydrogenation of phytoene, whereas nicotine does not lead to an accumulation of lycopene. Separation and identification of polyprenoid lipids was performed by HPLC. The properties and advantages of the chromoplast system are discussed.Abbreviations IPP isopentenyl pyrophosphate - TLC thin-layer chromatography - HPLC high pressure liquid chromatography - GC gas chromatography - Sau 6706 4-chloro-5-(dimethylamino)-2-,,-(trifluoro-m-tolyl)3(2H)-pyridazinone     

Physiological factors determining formation of plastocyanin and plastidic cytochrome c-553 in Scenedesmus

Physiological conditions necessary for the formation of plastocyanin and the concurrent cessation of cytochrome c-553 formation were studied in cells of copper-deficient Scenedesmus acutus after the addition of copper. Plastocyanin is formed after a lag-phase, leaving constant the content of plastidic cytochrome c-553. Therefore, the concentration of plastocyanin per cell increases and the concentration of cytochrome c-553 decreases during growth. Formation of plastocyanin during the induction period studied is dependent on light intensity. In the dark, there is a 90% inhibition, whereas under light intensities above 50 Wm^-2, a ratio of 1.3 molecules plastocyanin per 1,000 molecules chlorophyll is attained.Plastocyanin formations is inhibited by the uncoupler carbonylcyanide-p-trifluoromethoxy phenylhydrazone (FCCP), but not by moderate concentrations of 3-[3,4-dichlorophenyl]-1,1-dimethylurea (DCMU), and by keeping the algae under a nitrogen atmosphere without CO₂. Concurrently, the cultures treated with FCCP show a decreased endogenous ATP level. The ATP is necessary for plastocyanin formation.Abbreviations FCCP carbonylcyanide-p-trifluoromethoxyphenylhydrazone - DCMU 3-[3,4-dichlorophenyl]-1,1-dimethylurea - pcv packed cell volume