Title: Glomalin production and accumulation in soilless pot cultures Author
Submitted to: Canadian Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 17, 2010
Publication Date: December 1, 2010
Citation: Nichols, K.A. 2010. Glomalin production and accumulation in soilless pot cultures. Canadian Journal of Soil Science. 90:567-570. doi:10.4141/CJSS09041 Interpretive Summary: Hyphal growth, and presumably glomalin production, of arbsucular mycorrhizal (AM) fungi are dependent upon photosynthetic carbon from the plant. In this study, hyphal production and glomalin accumulation were measured in a root chamber and a hyphal chamber separated by a 38-µm nylon mesh bag. Values indicated a flush of glomalin production in the spring and summer [the second round of 14-weeks for one AM species (Glomus etunictum) and the first round for the other species (Gigaspora rosea)] with increased ambient irradiance and presumably photosynthetic activity. However, although large amounts of hyphae were collected, there was no direct relationship between hyphal and glomalin amounts, and there was no significant increase in these amounts over three 14-week culturing periods. To keep the plants from becoming root-bound, the root chambers were removed after each 14-week period and replaced by a new chamber with uninoculated corn seeds. This would have broken the connection between the roots and fungal hyphae, which would have caused carbon to be allocated to forming a new connection with the new plants at the beginning of each culturing period rather than continuing hyphal growth and glomalin production. In addition, the volume of the hyphal and root chambers may have affected carbon allocation, hyphal growth patterns, and glomalin production. Finally, glomalin may have been washed through the bottom of the pot when the pots were watered, which would have impacted glomalin accumulation and its correspondence with hyphal production.
Technical Abstract: Arbuscular mycorrhizal (AM) fungi form a symbiotic relationship with about 90% of all vascular plants. In this relationship, the fungus receives carbon from the plant in exchange for nutrients and water that the fungus picks up from the soil. Glomalin is a recalcitrant glycoprotein produced by AM fungi and has been measured in concentrations ranging from 2 to 15 mg glomalin g-1 soil. A soilless pot culture system with a sand and crushed coal potting medium and a root chamber separated from a hyphal chamber by a seamless 38-µm nylon mesh bag was used to measure total glomalin accumulation after each of three consecutive 14-week culturing periods. Corn (Zea mays) seedlings inoculated with one of two species of AM fungi (Gigaspora rosea or Glomus etunicatum) were planted in the root chamber. Glomalin was measured in different sections of pots: 1) on AM colonized roots and hyphae in the root chamber, (2) on AM fungal hyphae and associated debris in the hyphal chamber, and (3) on sand:coal potting media in the hyphal chamber. Results showed that glomalin levels in the hyphal chamber did not increased with consecutive culturing. However, plant growth, hyphal weight and glomalin accumulation were affected by irradiance with greater production under high light conditions. Immunofluorescence assays, using an antibody specific against glomalin, showed glomalin on hyphae of AM fungi and on a square of horticultural mesh covering the drain holes at the bottom of the pot. It was concluded that because of the large amount of glomalin on this mesh, the high flow-through watering system, and the large pore space and low surface charge of the sand:coal media much of the freshly-produced glomalin was lost through the bottom of the pot.