Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 7/13/2008
Publication Date: N/A
Interpretive Summary: Arbuscular mycorrhizal (AM) fungi live together with roots of many important crop plants. They can obtain minerals from the soil, especially phosphorus (P), and give them to a host plant in exchange for sugar molecules generated from photosynthesis. This symbiotic association is most beneficial for plants grown in low P soils. It is known that compounds exuded (given off by the plant root) stimulate fungal growth and enhance the colonization of host roots. To understand changes in host plant metabolism due to P stress, which directly affects exuded compounds, identification of metabolites found in the exudate is essential. A recent development in methodology, called Fourier Transform Ion Cyclotron Mass Spectrometry (FTMS), produces an extremely high resolution and very accurate determination of chemical masses from a very complex mixture. Some of the compounds identified with FTMS were lipids and secondary metabolites which shows that lipid metabolic from secondary metabolic pathways are effected by plants grown under P stress .
Technical Abstract: To see if differences in the metabolite content of exudates obtained from cultured carrot roots grown in the presence and absence of phosphorus could be detected, crude samples were analyzed via Fourier Transform Ion Cyclotron Mass Spectrometry (FTMS). The highly accurate masses and elemental compositions allowed for the identification of many of these metabolites, although some are unknown. Some identified metabolites were lipids, lignins, flavones, secondary metabolites or acidic compounds, and some were lactone derivatives. Within the global or total metabolite population, a pool of compounds was found to be elevated under phosphorus stress conditions. The identity of these compounds was of interest since it is known that the growth and hyphal branching of arbuscular mycorrhizal fungi is greatly increased by compounds elevated in roots grown in the absence of Pi.