Impact of increased ultraviolet-B radiation stress due to stratospheric ozone depletion on N2 fixation in traditional African commercial legumes
Journal Article
2004
Permanent link to this Item
Authors
Journal Title
South African Journal of Botany
Journal ISSN
Volume Title
Publisher
Publisher
University of Cape Town
Department
Faculty
License
Series
Abstract
Reports of diminished nodule formation and nitrogenase activity in some Asian tropical legumes exposed to above-ambient levels of ultraviolet-B (UV-B: 280–315nm) radiation have raised concerns as to the impact of stratospheric ozone depletion on generally poorly developed traditional African farming systems confronted by the high cost and limited availability of chemical fertilisers. These rely on N2-fixing legumes as the cheapest source of N for maintaining soil fertility and sustainable yields in the intrinsically infertile and heterogeneous African soils. In view of this, we examined the effects of supplemental UV-B radiation approximating 15% and 25% depletions in the total ozone column on N2 fixation in eight traditional African commercial legume species representing crop, forest, medicinal, ornamental and pasture categories. In all categories examined, except medicinal, supplemental UV-B had no effect on root non-structural carbohydrates, anthocyanins and flavonoids, known to signal Rhizobiaceae micro-symbionts and promote nodule formation, or on nodule mass, activity and quantities of N fixed in different plant organs and whole plants. In contrast, in the medicinal category Cyclopia maculata (Honeybush) a slow growing commercially important herbal beverage with naturally high flavonoid concentrations, displayed decreased nodule activity and quantities of N fixed in different plant organs and whole plants with increased UV-B. This study’s findings conclude negligible impacts of ozone depletion on nitrogen fixation and soil fertility in most traditional African farming systems, these limited to occasional inhibition of nodule induction in some crops.
Description
Reference:
Chimphango, S. B. M., Musil, C. F., Dakora, F. D., & van Staden, J. (2004). Impact of increased ultraviolet-B radiation stress due to stratospheric ozone depletion on N 2 fixation in traditional African commercial legumes. South African Journal of Botany, 70(5), 790-796.