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1999 (1)
1982 (1)
1Author    AdH C M Schapendonk3, M. Arcel, VanO. Ijen, SanderC. Pot3, Riki Van Den Boogaardb, Jerem, H. ArbinsonbRequires cookie*
 Title    Nitrogen Shortage in a Tomato Crop; Scaling up from Effects on Electron-Transport Rate to Plant Productivity  
 Abstract    Optimization of nitrogen supply in a tomato plant is stepwise assessed, from chloroplast characteristics to whole crop performance. Experiments are reported in which important key processes are quantified in relation to the nitrogen content of leaves. Interactions of N effects with leaf aging and canopy light distribution are analyzed. A simulation model that integrates this knowledge is constructed. The results of three nitrogen partitioning scenarios for Rubisco suggest that optimization of the distribution of Rubisco between leaf layers is less important for plant productivity than within-leaf optimiza­ tion of the photosynthetic apparatus. 
  Reference    Z. Naturforsch. 54c, 840—8 (1999); received November 12 1998/March 3 1999 
  Published    1999 
  Keywords    Stress, Nitrogen Optimization, Photosynthesis, Tomato, Modelling 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0840.pdf 
 Identifier    ZNC-1999-54c-0840 
 Volume    54 
2Author    P. Schreier, G. LorenzRequires cookie*
 Title    Separation, Partial Purification and Characterization of a Fatty Acid Hydroperoxide Cleaving Enzyme from Apple and Tomato Fruits  
 Abstract    A membrane-bound enzyme catalysing the cleavage o f 13-hydroperoxy-(Z)-9,(£)-l 1-oc-tadecadienoic acid (13-LHPO) and 13-hydroperoxy-(Z)-9,(£)-ll,(Z)-15-octadecadienoic acid (13-LnHPO) to C6-aldehydes was isolated and partially purified from apples and tomatoes. At­ tempts to employ Ultrogel AcA 34 and AcA 22 in a gel chromatographic purification step were partially frustrated by reaggregation phenomena. However, by using Sepharose CL-4 B an en­ zyme fraction (MW 200 000 Da) with lipoxygenase and fatty acid hydroperoxide cleaving activity could be separated from a high molecular-weight active eluate. By applying preparative isoelec­ tric focussing to the tomato protein we succeeded in separating the fatty acid cleaving activity from the lipoxygenase, because o f their different isoelectric points of pH 5.8 -6 .1 and pH 5.0, re­ spectively, An 8.4-fold purification o f the fatty acid cleaving activity was achieved. A pH-op-timum of 5.5 and a K m-value o f 2.6 x 10~5 m/1 for the 13-hydroperoxide o f linoleic acid were mea­ sured. p-Chloromercuribenzoic acid (1 mM) showed significant inhibitory effect on the fatty acid hydroperoxide cleaving enzyme, but no evidence o f inhibition was found with 1 mM H20 2, KCN, DABCO and EDTA or superoxide dismutase (270 U). The maximum amount of fatty acid hydroperoxide decomposition (C8-aldehyde formation) was determined to be 59%. 
  Reference    Z. Naturforsch. 37c, 165—173 (1982); received August 18/N ovem ber 24 1981 
  Published    1982 
  Keywords    Apples, Tomatoes, Fatty Acid Hydroperoxides, Cleavage Enzyme, Cg-Aldehydes 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0165.pdf 
 Identifier    ZNC-1982-37c-0165 
 Volume    37