Piper, Frida I., Gabriela Baez, Alejandra Zúñiga-Feest, and Alex Fajardo. 2013. Soil nitrogen, and not phosphorus, promotes cluster-root formation in a South American Proteaceae, Embothrium coccineum. American Journal of Botany 100:2328-2338. doi:10.3732/ajb.1300163 Reported at Eurekalert, January 23, 2014