ZfN: Search Results

1	Author	K. H. Grumbach	Requires cookie*
	Title	Interconversion of Carotenoids and Quinones after Onset of Photosynthesis in Chloroplasts of Higher Plants
	Abstract	The interconversion of carotenoids and quinones was investigated in beech and spinach leaves as well as isolated intact spinach chloroplasts following a dark-light transition. It is shown that isolated intact chloroplasts which are preincubated for 2 h at pH 7.6 in the dark and re illuminated with strong white light are capable not only o f deepoxidizing violaxanthin into antheraxanthin and zeaxanthin but simultaneously change the redox state o f the plastoquinone-pool in their thylakoid membrane. At the same time as violaxanthin is deepoxidized plasto-hydroquinone-9 is oxidized to plastoquinone-9. If the light is turned off zeaxanthin is epoxidized into antheraxanthin and violaxanthin but no significant change in the redox state o f the plasto-quinone-pool occurred. It is concluded that the deepoxidation of violaxanthin is connected to the photosynthetic electron transport in that way that an acidification o f the intrathylakoidal compartment by the vectorial release of protons from the water photooxidizing enzyme system and the plastoquinone-pool is required for the activation of the violaxanthin deepoxidase. This may be taken as further evidence that violaxanthin deepoxidase is located at the inner side o f the thylakoid membrane. Additional evidence for this location site is given by the observation that neither deepoxidation of violaxanthin nor photooxidation of plastohydroquinone-9 occurred after onset o f photosyn thesis if non cyclic electron transport was inhibited by DCMU.
	Reference	Z. Naturforsch. 38c, 393 (1983); received March 15 1983
	Published	1983
	Keywords	Carotenoids, Photosynthesis, Quinones, Xanthophyll Cycle
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	TEI-XML for	default:Reihe_C/38/ZNC-1983-38c-0393.pdf
	Identifier	ZNC-1983-38c-0393
	Volume	38

2	Author	G. E. Laskay, I. M. Lehoczki, L. Aróti, Szalay	Requires cookie*
	Title	Effects of Pyridazinone Herbicides during Chloroplast Development in Detached Barley Leaves I. Effects on Pigment Accumulation and Fluorescence Properties
	Abstract	The effects o f three differently substituted pyridazinone herbicides on the accum ulation o f photosynthetic pigments and on the fluorescence properties o f greening barley leaves were studied. The two trifluoro-methyl derivatives, SAN 6706 and 9789 caused inhibition in the accumulation o f carotenes only after the First 24 h o f greening. By the 48th hour o f greening no detectable amounts o f carotenes were present in the treated leaves. Considerable am ounts o f xanthophylls however remained present, and no bleaching o f the leaves was observed. It is suggested that SAN 6706 and 9789 prevent the formation o f the enzym e(s) catalyzing the desaturation o f phytoene and phytofluene. Fluorescence spectra indicate that the organization o f pigment forms altered seriously in the treated leaves. This experimental system may be useful to study the action o f pyridazinone herbicides without causing com plete photobleaching o f the photosynthetic apparatus. SAN 9785 had only minor effects on pigment accum ulation and also on the organization o f pigment forms. The possible explanations o f the effects observed are dis cussed.
	Reference	Z. Naturforsch. 38c, 736—740 (1983); received June 8 1983
	Published	1983
	Keywords	Pyridazinone Herbicides, Carotenoids, Fluorescence Spectrum
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	TEI-XML for	default:Reihe_C/38/ZNC-1983-38c-0736.pdf
	Identifier	ZNC-1983-38c-0736
	Volume	38

3	Author	K.H G Rum Bach	Requires cookie*
	Title	Distribution of Chlorophylls, Carotenoids and Quinones in Chloroplasts of Higher Plants
	Abstract	Leaves, cotyledons, isolated chloroplasts and subplastid fractions (thylakoids and envelopes) o f radish (Raphanus sativus L. cv. Saxa) and spinach (Spinacia oleracea L. cv. M atador) were assayed for their pigment and quinone content and com position. Virtually all the chlorophylls, carotenoids and quinones were contained in the thylakoids. Envelopes prepared by the method described contained very low amounts o f chlorophyll a and b, violaxanthin and neoxanthin, but no /7-carotene, lutein, zeaxanthin and antheraxanthin. Am ong the quinones trace am ounts o f plastoquinone and a-tocopherol but no plastohydroquinone, a-tocoquinone and phylloquinone were detected. Presented data may be taken as evidence that in vivo the chloroplast envelope is not a location site o f carotenoids and quinones as generally accepted. Possible im plications for the biosyntheses o f quinones and pigments are discussed.
	Reference	Z. Naturforsch. 38c, 996—1002 (1983); received August 16 1983
	Published	1983
	Keywords	Carotenoids, Chlorophylls, Chloroplasts, Envelopes, Quinones, Thylakoids
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	TEI-XML for	default:Reihe_C/38/ZNC-1983-38c-0996.pdf
	Identifier	ZNC-1983-38c-0996
	Volume	38

4	Author	H. Erm, Ann Bothe, Gislene Barbosa, JohannaD.	Requires cookie*
	Title	Nitrogen Fixation and Nitrate Respiration by A zospirillum brasilense
	Abstract	Azospirillum The 0 2-sensitivitiy of N 2-fixation by the carotenoid forming strain Azospirillum brasilense Cd and the colourless strain Sp 7 is com pared in the present communication. As no difference in the reaction is observed with both strains, it is concluded that carotenoids do not protect nitrogenase from damage by 0 2. Azospirillum spp. have also been shown to perform N O '-dependent ^ -f i x ation. The physiological properties of this reaction are described in more detail in the present communication. Evidence is presented that NO^-dependent N 2-fixation is a transitory reaction, proceeding only as long as the enzymes o f assimilatory nitrate reduction are synthesized by the cells.
	Reference	Z. Naturforsch. 38c, 571—577 (1983); received March 31 1983
	Published	1983
	Keywords	Nitrogen Fixation, N itrate Respiration, Denitrification, Nitrogenase Protection, Carotenoids
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	TEI-XML for	default:Reihe_C/38/ZNC-1983-38c-0571.pdf
	Identifier	ZNC-1983-38c-0571
	Volume	38