High potential, but low actual, glycine uptake of dominant plant species in three Australian land-use types with intermediate N availability

• Published in: Plant and Soil
• Main Authors: Kahmen, Ansgar, Livesley, Stephen J., Arndt, Stefan K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: eScholarship, University of California 2009
• Subjects: Life Sciences; Ecology; Plant Physiology; Soil Science & Conservation; Plant Sciences; Amino acids; Glycine; Microbial competition; Mineral nutrition; Stable isotopes; Arctic
• Online Access: http://www.escholarship.org/uc/item/8nv8k7br

The traditional view of the nitrogen (N) cycle has been challenged since the discovery that plants can compete with microbes for low molecular weight (LMW) organic N. Despite a number of studies that have shown LMW organic N uptake by plants, there remains a debate on the overall ecological relevance of LMW organic N uptake by plants across ecosystems with different N availabilities. We here report patterns of glycine N uptake by plants from three different Australian land-use types with intermediate N availability and low inherent glycine concentrations in the soil. Using 15N labeled tracers, we tested the potential of these plants to acquire glycine in ex-situ laboratory experiments and attempted to validate these results in the field by determining actual uptake of glycine by plants directly from the soil. We found in the ex-situ experiments that plants from all three land-use types were able to take up significant amounts of glycine. In contrast, glycine uptake directly from the soil was minimal in all three land-use types and 15N tracers were largely immobilized in the soil organic N pool. Our study confirms that the potential for LMW organic N uptake by plants is a widespread phenomenon. However, our in-situ experiments show that in the three land-use types tested here plants are inferior competitors for LMW organic N and rely on NH 4 + as their main N source. In contrast to several previous studies in arctic, alpine and even temperate ecosystems, our study suggests that in ecosystems with intermediate N availability, mineral N is the plants’ main N source, while LMW organic N is of less ecological relevance to plant N nutrition.