|AVILA-OSUNA, P - NEW MEXICO STATE UNIV
Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2001
Publication Date: 7/1/2002
Citation: BARROW, J.R., AVILA-OSUNA, P. PHOSPHORUS SOLUBILIZATION AND UPTAKE BY DARK SEPTATE FUNGI IN FOURWING SALTBUSH, ATRIPLEX CANESCENS (PURSH) NUTT. JOURNAL OF ARID ENVIRONMENTS. 2002. V. 51. P. 449-459.
Interpretive Summary: A fungus, carried by the seed, was isolated from the roots of fourwing saltbush, an important forage shrub in desert rangelands. Experiments showed that the fungus grows inside the roots and into the soil, and supplies phosphorus that is otherwise unavailable to the plant and improves plant growth. This symbiotic association between the plant and fungus improves the chances for plant establishment, productivity, and survival o arid rangelands.
Technical Abstract: Fourwing saltbush, Atriplex canescens (Pursh) Nutt., is an ecologically important range plant in arid southwestern USA rangelands. Native populations of this non-mycorrhizal, chenopodiacious shrub are extensively colonized by melanized dark septate fungi (DS). Seedling radicles of A. canescens are colonized at germination by a DS fungus identified as Aspergillus ustus that cannot be removed by heat or sterilization. The mutualistic association of A. canescens and A. ustus was evaluated by comparing plants treated with either no P (0P) or adequate plant available soluble P (30 ppm) in the root zone (AAP). Plant unavailable P (as rock phosphate (RP) or tricalcium phosphate (TCP)) was separated from the roots by a barrier that only allowed the passage of fungi. Plant roots in all treatments were internally colonized by A. ustus. A significant mutualistic response was observed in the RP and TCP treatments. Evidence for enhanced P uptake by the plant via the fungus was greater shoot and root biomass production and fungal density. Plants receiving P from plant unavailable P from TCP below the barrier via the fungus had equivalent shoot biomass and greater root biomass (P< 0.01) than plants receiving soluble P (AAP). Phosphorus use efficiency was increased in plants supplied P by fungi from plant unavailable P treatments. It was concluded that A. ustus utilized plant carbon for growth and the solubilization, uptake and transport of P to enhance shoot and root biomass. The potential benefits of DS fungi in arid ecosystems is discussed.