caa a22 4500 605480923 CHVBK 20210128100418.0 cr unu---uuuuu 210128e20151201xx s 000 0 eng 10.1007/s11099-015-0144-z doi (NATIONALLICENCE)springer-10.1007/s11099-015-0144-z Assessing the relationship between photosynthetic C accumulation and symbiotic N nutrition in leaves of field-grown nodulated cowpea ( Vigna unguiculata L. Walp.) genotypes [Elektronische Daten] [A. Belane, F. Dakora] This study evaluated the relationship between photosynthetic carbon accumulation and symbiotic nitrogen nutrition in young fully expanded leaves of 30 nodulated cowpea genotypes grown in the field at Manga, Ghana, in 2005 and 2006. Estimates of fixed-N in photosynthetic leaves revealed greater symbiotic N in genotypes with higher photosynthetic rates and increased leaf transpiration rate/efficiency. There was also greater C accumulation in genotypes with higher symbiotic N and/or total N. Additionally, genotypes with high contents of C per unit of leaf total N exhibited greater C per unit of leaf N-fixed. The C/N and C/Rubisco-N ratios were generally similar in their magnitude when compared to the C/N-fixed ratio due possibly to the fact that Rubisco accounts for a high proportion of photosynthetic leaf N, irrespective of whether the enzyme was formed from soil N or symbiotic N. Cowpea genotypes that relied heavily on soil N for their N nutrition exhibited much higher C/N-fixed ratios, while conversely those that depended more on symbiosis for meeting their N demands showed markedly lower C/N-fixed values. For example, genotypes Omondaw, Bensogla, IT93K-2045-29, and Sanzie, which respectively derived 83.9, 83.1, 82.9, and 76.3% N from fixation, recorded lower C/N-fixed ratios of 10.7, 12.2, 12.1, and 13.0 mg mg−1 in that order in 2005. In contrast, genotypes Botswana White, IT94D-437-1, TVu1509, and Apagbaala, which obtained 14.8, 15.0, 26.4, and 26.0% of their N nutrition from fixation, showed high C/N-fixed values of 84.0, 69.0, 35.2, and 40.6 mg.mg−1, respectively, in 2005. This clearly indicates that genotypes that obtained less N from symbiosis and more N from soil revealed very high C/N-fixed values, an argument that was reinforced by the negative correlations obtained between the three C/N ratios (i.e. C/N, C/Rubisco-N, and C/N-fixed) and leaf N concentration, percentage nitrogen derived from fixation, total N content, amount of N-fixed, and Rubisco N. These data suggest a direct link between photosynthetic C accumulation and symbiotic N assimilation in leaves of nodulated cowpea, and where genotypes derived a large proportion of their N from fixation, photosynthetic C yield substantially increased. The Institute of Experimental Botany, 2015 N2 fixation nationallicence photosynthesis nationallicence photosynthetic fixed-N use efficiency nationallicence transpiration efficiency nationallicence δ15N nationallicence Chl : chlorophyll nationallicence E : transpiration rate nationallicence g s : stomatal conductance nationallicence %Ndfa : percentage of nitrogen derived from fixation of atmospheric N2 nationallicence P N : net photosynthetic rate nationallicence PNUE : photosynthetic nitrogen use efficiency nationallicence DAP : days after planting nationallicence δ15N : nitrogen isotopic composition nationallicence Belane A. Department of Crop Sciences, Tshwane University of Technology, 175 Nelson Mandela Drive, Private Bag X680, 0001, Pretoria, South Africa aut Dakora F. Chemistry Department, Tshwane University of Technology, 175 Nelson Mandela Drive, Private Bag X680, 0001, Pretoria, South Africa aut Photosynthetica The Institute of Experimental Biology of the Czech Academy of Sciences 53/4(2015-12-01), 562-571 0300-3604 53:4<562 2015 53 11099 https://doi.org/10.1007/s11099-015-0144-z text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s11099-015-0144-z text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Belane A. Department of Crop Sciences, Tshwane University of Technology, 175 Nelson Mandela Drive, Private Bag X680, 0001, Pretoria, South Africa aut NATIONALLICENCE 700 1- Dakora F. Chemistry Department, Tshwane University of Technology, 175 Nelson Mandela Drive, Private Bag X680, 0001, Pretoria, South Africa aut NATIONALLICENCE 773 0- Photosynthetica The Institute of Experimental Biology of the Czech Academy of Sciences 53/4(2015-12-01), 562-571 0300-3604 53:4<562 2015 53 11099