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Title: Photosynthesis, assimilate partitioning and responses to carbon dioxide enrichment in barley mutants deficient in nadh dependent nitrate reductase

Author
item SICHER JR, RICHARD
item Bunce, James

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/12/2006
Publication Date: 10/3/2006
Citation: Sicher Jr., R.C., Bunce, J.A. 2006. Photosynthesis, assimilate partitioning and responses to carbon dioxide enrichment in barley mutants deficient in nadh dependent nitrate reductase [abstract]. American Society of Plant Biologists Annual Meeting. p.165.

Interpretive Summary:

Technical Abstract: Photosynthesis rates and photosynthate partitioning were determined for WT and two "isogenic" barley mutants (H. vulgare cv. Steptoe) deficient in NADH:NR activity. The two mutations were at separate loci, with nar1 affecting the NR structural gene and nar2, which is pleiotropic, affecting the molybdo cofactor. Both barley mutants contained low amounts of a separate, bispecific NR that utilizes NADPH. Seedlings were grown in pots for 3 to 6 weeks either in controlled environment chambers or in a temperature controlled glasshouse. Assimilation rates (A) and Ci of the two mutant lines were lower than that of the WT when measured at 36 and 96 Pa CO2. These differences were more evident when plants were grown in atmospheres with elevated rather than ambient CO2. Total biomass accumulation differed among genotypes with WT > nar1 > nar 2. Dry matter accumulation by all three genotypes was increased in the elevated compared to the ambient CO2 treatment. When grown on a complete mineral nutrient solution, foliar nitrate concentrations were up to 2-fold greater in the mutant lines compared to the WT. Conversely, [Pi], specific amino acids and total soluble protein levels were decreased in the mutants versus the WT. Nitrate assimilation measured in the dark for 24-h using excised leaves was detected in all 3 genotypes. However, after a 6-h incubation period nitrate assimilation was only detected in the WT.