Root exudates: a pathway for short-term N transfer from clover and ryegrass

• Published in: Plant and soil 2001-02, Vol.229 (2), p.235-243
• Main Authors: Paynel, Florence, Murray, Philip J, Cliquet, Jean Bernard
• Format: Article
• Language: English
• Subjects: Acid soils; Agronomy. Soil science and plant productions; Amino acids; Ammonium; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Clover; Exudation; Fundamental and applied biological sciences. Psychology; General agroecology; General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping; General agronomy. Plant production; Generalities. Agricultural and farming systems. Agricultural development; Grasses; Grassland soils; Legumes; Life Sciences; Nitrogen; Nutrient flow; Nutrient solutions; Plant roots; Plant species; Plants; Roots; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Synecology; Terrestrial ecosystems; Vegetal Biology
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/A:1004877214831

The short-term transfer of nitrogen (N) from legumes to grasses was investigated in two laboratory studies. One study was done in pots where the roots of white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) were allowed to co-exist, and a second study was performed using a micro-lysimeter system designed to maintain nutrient flow from the clover to the grass, whilst removing direct contact between the root systems. The ¹⁵N-dilution technique was used to quantify the transfer of N between species. Levels of ammonia and amino acids were measured in root exudates. The amounts of N transferred were in the same order of magnitude in both the pot and micro-lysimeter experiments. In the micro-lysimeter experiment, 0.076 mg of N were transferred per plant from clover to ryegrass during the course of the experiment. Ammonium exudation was much higher than amino acid exudation. The most abundant amino acids in both clover and ryegrass root exudates were serine and glycine. However, there was no correlation between the free amino acid profile of root extracts and exudates for both plant species: Asparagine was the major amino acid in clover roots, while glutamine, glutamate and aspartate were the major amino acids in ryegrass roots. Comparison of exudates obtained from plants grown in non-sterile or axenic conditions provides evidence of plant origin of ammonium, serine and glycine.