An assessment of symbiotic Nnutrition in species of the genus Aspalathus endemic to the Cape Floristic Region of South Africa
Pampa, Joshua M. Ngwenya, Zanele D. Mpai, Tiisetso Dakora, Felix D.
Pampa, Joshua M.
Ngwenya, Zanele D.
Mpai, Tiisetso
Dakora, Felix D.
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Abstract
Nitrogen fixation is important for the growth and yield of nodulated legumes. In this study, the 15N naturalabundance technique was used to assess the symbiotic N nutrition of 15 Aspalathus species sampled from 13locations. The results showed that all 15 species met part of their N requirements from N2 fixation, as shownby the different levels of symbiotic dependency. Seven species, for example, derived 54 to 77% of their Nnutrition from symbiosis, nine obtained 36 to 49% from fixation, and five species derived ˂ 20% of their Nfrom the atmosphere. More specifically, A. acuminata and A. clada both from Worcester Langerug derived76.5% and 72.1% N, respectively, from symbiosis, A. acuminata from Rondebosch obtained 68.4% N, A. acumi-nata from Kalbaskraal 59.5% N, A. aculeata from Mamesbury 56.8% N, A. divericata from Penhill 56.6% N and A.cordata from Dutoitkloof 53.9% N from the atmosphere. In contrast, A. zeyheri sampled from Kokrivier derived only 4.3% of its N from symbiosis, followed by A. capensis (13.3%) and A. carnosa (14.6%) both from Silverline's C/N values found for the Aspalathus species in this study were unusually high for a legume, and could suggest an ecological adaptation to the low N soils of the Cape fynbos as under such N-poor plants metaboli-cally switch from N-containing storage compounds to N-free storage molecules such as sucrose and glycerol, glucosides, galactoses and disaccharides.
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Date
2023-05-26
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Elsevier B.V.
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Keywords
15N natural abundance, %N derived from fixation, N values, N-fixed, C/N ratio, Rhizosphere soil, Cape fynbos