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Abstract
The conversion of the Brazilian savannas for pastures and agricultural use has caused the species Dimorphandra wilsonii (Fabaceae-Caesalpinioideae) to become isolated and restricted to areas occupied by African grasses of Urochloa sp. This highly endangered tree species was cultivated in the presence of Bradyhizobium japonicum (symbiont 1), Glomus etunicatum (symbiont 2), and Urochloa decumbens in low nitrogen (N) availability in order to evaluate its growth in these experimental conditions. Even though the nodulation and mycorrhization was of low occurrence, the inoculated plants with symbionts had the greatest nitrogen and chlorophyll content, photosynthetic radiation use efficiency, and biomass accumulation in relation to the plants which had not been inoculated and/or cultivated in the presence of U. decumbens. The results suggest effective N2 fixation, independent of the localization of bacteria, whether in the root tissue interior or free in the rhizosphere. Therefore, the presence of N2-fixing bacteria can benefit the early growth of D. wilsonii, whereas the occurrence and aggressive persistence of U. decumbens can limit this development, increasing the threat of extinction of this species in their habitat.
Acknowledgements
The authors thank the Coordination for the Improvement of Higher Education Personnel (CAPES) for foreign research grants (Environmental Biology Center, Science Faculty of the University of Lisbon, Portugal), the Postgraduate program in Plant Biology of the Federal University of Minas Gerais (UFMG), and the Foundation of Zoological Botany in Belo Horizonte, Brazil. The authors also thank Alistair Hayward for the translation and critical review of the original Portuguese text.