The Oxalate-Carbonate Pathway of Brosimum alicastrum Sw.; Moraceae

This source preferred by Iain Green

Authors: Rowley, M.C., Estrada - Medina, H., Tzec - Gamboa, M., Rozin, A., Cailleau, G., Verrecchia, E.P. and Green, I.D.

Start date: 13 August 2017

The oxalate - carbonate pathway (OCP) is a biogeochemical process involving plants, fungi and bacteria that transforms atmospheric CO 2 into CaCO 3 . However, until now the process has only been studied in acidic soil environments adjacent to species that have limited food - production potential .

This study used an experimental approach to evaluate an OCP associated with Brosimum alicastrum , a Neotropical species that produces significant quantites of food ( ca.

70 – 200 kg - seeds yr −1 ), in the calcareous soils of Haiti and Mexico. Enzymatic analysis of various tissues from B. alicastrum indicated that the species produces significant amounts of calcium oxalate (5.97 % D.W.) at all sample sites. Oxalotroph y , the bacterial metabolism of calcium oxalate that leads to the precipitation of CaCO 3 , was also confirmed with microbiological analyses in both countries.

T he typical localised alkalinisation and identification of secondary carbonate associated with the OCP was obscured at most sample sites by h igh concentrations of lithogenic carbonate and total cal cium (>7 g kg −1 ), except at Ma Rouge, Haiti. Soils adjacent to subjects in Ma Rouge presented a localised increase in CaCO 3 concentration (5.9 %) and pH (0.63) .

F indings in Ma Rouge , coupled with observations of root - like secondary carbonate deposits in Me xico, strongly impl y that the OCP can also occur in calcareous soils. Th us, this study confirms that the OCP acts in calcareous soils, adjacent to species with significant food - production potential, and could play a fundamental and un - accounted role in the global calcium - carbon coupled cycle

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