ISSN:
1573-5079
Keywords:
ammonia fixation
;
light
;
photorespiration
;
Zea Mays L
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The effect of light on the metabolism of ammonia was studied by subjecting detached maize leaves to 150 or 1350 μmol m−2 s−1 PAR during incubation with the leaf base in 2 mM 15NH4Cl. After up to 60 min, leaves were extracted. Ammonia, glutamine, glycine, serine, alanine, and aspartate were separated by isothermal distillation and ion exchange chromatography. 15N enrichments were analyzed by emission spectroscopy. The uptake of ammonium chloride did not influence CO2 assimilation (8.3 and 17.4 μmol m−1 s−1 at 150 and 1350 μmol m−2 s−1 PAR, respectively). Leaves kept at high light intensity contained more serine and less alanine than leaves from low light treatments. Within 1 h of incubation the enrichment of ammonia extracted from leaves rose to approximately 20% 15N. In the high light regime the amino acids contained up to 15% 15N, whereas in low light 15N enrichments were small (up to 6%). The kinetics of 15N incorporation indicated that NH3 was firstly assimilated into glutamine and then into glutamate. After 15 min 15N was also found in glycine, serine and alanine. At high light intensity nearly half of the 15N was incorporated in glycine. On the other hand, at low light intensity alanine was the predominant 15N sink. It is concluded that light influences ammonia assimilation at the glutamine synthetase reaction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00049278
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