Related Experiment Video
Updated: May 29, 2026

Collection of Alfalfa Root Exudates to Study the Impact of Di(2-ethylhexyl) Phthalate on Metabolite Production
Published on: June 2, 2023
Citramalic acid and salicylic acid in sugar beet root exudates solubilize soil phosphorus
Reza Khorassani1, Ursula Hettwer, Astrid Ratzinger
1Department of Crop Science, Plant Nutrition, Georg-August-University Göttingen, Carl-Sprengel-Weg 1, D-37075 Goettingen, Germany.
Background:
In soils with a low phosphorus (P) supply, sugar beet is known to intake more P than other species such as maize, wheat, or groundnut. We hypothesized that organic compounds exuded by sugar beet roots solubilize soil P and that this exudation is stimulated by P starvation.
Results:
Root exudates were collected from plants grown in hydroponics under low- and high-P availability. Exudate components were separated by HPLC, ionized by electrospray, and detected by mass spectrometry in the range of mass-to-charge ratio (m/z) from 100 to 1000. Eight mass spectrometric signals were enhanced at least 5-fold by low P availability at all harvest times. Among these signals, negative ions with an m/z of 137 and 147 were shown to originate from salicylic acid and citramalic acid. The ability of both compounds to mobilize soil P was demonstrated by incubation of pure substances with Oxisol soil fertilized with calcium phosphate.
Conclusions:
Root exudates of sugar beet contain salicylic acid and citramalic acid, the latter of which has rarely been detected in plants so far. Both metabolites solubilize soil P and their exudation by roots is stimulated by P deficiency. These results provide the first assignment of a biological function to citramalic acid of plant origin.
Related Concept Videos
Factors Affecting Solubility
The Phosphorus Cycle
Responses to Salt Stress
C4 Pathway and CAM
C4 Pathway
The C4 pathway is used by plants such as...
Water and Mineral Acquisition
Adaptations that Reduce Water Loss

