
%0 Journal Article
%A Isopp, Hubert 
%A Frehner, Marco 
%A Almeida, José P. F. 
%A Blum, Herbert 
%A Daepp, Markus 
%A Hartwig, Ueli A. 
%A Lüscher, Andreas 
%A Suter, Daniel 
%A Nösberger, Josef 
%T Nitrogen plays a major role in leaves when source-sink relations change: C and N metabolism in <emph type="2">Lolium perenne</emph> growing under free air CO<emph type="8">2</emph> enrichment
%J Functional Plant Biology
%D 2000/09/01
%V 27
%N 9
%P 851-858
%K 
%R https://doi.org/10.1071/PP99151
%U https://www.publish.csiro.au/paper/PP99151 
%X This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999 Swards of Lolium perenne L. were grown in the field in a long-term free air CO2 enrichment (FACE) facility. The CO2 treatment was combined with two levels of N fertilization and regular defoliation, which resulted in plants with a wide range of source&#8211;sink relations. C and N metabolism were investigated to assess the role of carbohydrate and nitrogenous compounds in leaves in indicating source&#8211;sink relations. Sucrose exhibited the largest changes in contents during the day&#8211;night cycle; therefore, it was identified as the main short-term storage compound for night-time export. Fructan accumulation indicated the degree of surplus C supply in the source compared to C use in sinks. Nitrate content depended mainly on N fertilization, and was reduced under elevated pCO2. Nitrate appeared to indicate a current surplus of available N relative to the need for growth. Amino acid content responded strongly to N fertilization but decreased only slightly under elevated pCO2. Protein content, however, decreased significantly under elevated pCO2. The patterns of diurnal changes of C or N compounds did not differ between CO2 treatments. Down-regulation of photosynthesis appeared to occur when plants were extremely N-limited as under elevated pCO2, low N and at a late regrowth stage. 
