A Potential Solution to the Nitrogen Dilemma in Modern Agriculture

In agricultural systems, nitrogen is a necessary component but its use comes at an economic and environmental cost.  The genus Gunnera is the only angiosperm having evolved a symbiosis with Nostoc, a cyanobacteria capable of supplying the nitrogen needs of its host.  We theorize this advantage may be transferred to crops via an integration of Nostoc and/or Gunnera symbiosis system that may supplement or replace the need for nitrogen fertilizer inputs.  The symbiosis is initiated through the establishment of Nostoc colonies in every Gunnera plant.  The Nostoc enters through a uniquely evolved gland facilitating the entrance of Nostoc alone.  To date, our understanding of the Gunnera-Nostoc symbiosis is limited.  Much of the published work has been conducted in controlled greenhouse and laboratory settings.  To further our understanding of the phenomenon as it occurs naturally, we examined Gunnera populations and the Gunnera-Nostoc symbiosis at Cloudbridge Reserve, in Costa Rica.  Gunnera functions as a disturbance colonizer, thus all populations examined were found on landslides.  Multiple species of Gunnera are present in Costa Rica.  At this site, we confirmed that Gunnera insignis is present based upon anatomical evidence.   No signs of hybridization were noted, a phenomenon that has been reported in Costa Rica.  Gunnera tissue of adult, rhizomatous plants and seedling, non-rhizomatous plants was examined ex situ for the presence of Nostoc colonies.  In adult rhizomes and juvenile crown tissue, we confirmed the presence of Nostoc.  Nostoc colonies were never confirmed in root, petiole or leaf tissue in any plant examined.  A distinctively different morphology was noted for juvenile and adult leaves, these data will be presented.