Lipid Physiology of Vesicular‐arbuscular Mycorrhiza

SUMMARY A microscopic and biochemical comparison was made of the distribution, quantity and composition of lipid in roots of onion, clover and ryegrass infected with the VA mycorrhizal fungus, Glomus mosseae , in uninfected roots and in the external mycelium from infected, aseptically grown onion roots. Abundant oil‐droplets were observed in the internal and external fungal mycelium, in the vesicles and chlamydospores, and adjacent to the appressoria at entry points. Mycorrhizal roots contained significantly more total lipid than uninfected roots. In estimations of separated lipid classes, the mycorrhizal roots consistently showed higher levels of triglyceride than non‐inycorrhizal roots. External mycelium contained high levels of neutral lipids, especially triglyceride, diglyceride and free fatty acids. Compared with uninfected roots, mycorrhizal onion roots contained higher levels of diphosphatidyl glycerol, phosphatidyl serine, phosphatidyl ethanolamine, phosphatidy) choline, phosphatidyl glycerol, phosphatidic acid and phosphatidyl inositol. With the exception of phosphatidyl inositol and phosphatidic acid, these were all prominent components of G. mosseae mycelium.