Redwood Reader

Glomalin III
This will wrap up my direct posting for glomalin for the time being. Serious researchers can find various ways to detect and quantify glomalin at: http://www.ba.ars.usda.gov/sasl/research/glomalin.html, Glomalin Methods and Materials. Then two more government research abstracts and another clarifier, this time by the rec.bonsai group. I have lost the link to the second article, but it is on the Tektran server.

A HYDROPHOBIC GLYCOPROTEINACEOUS SUBSTANCE PRODUCED BY MYCORRHIZAL FUNGI STABILIZES SOIL STRUCTUREAuthor(s):
MILLER R M
WRIGHT SARA E
JASTROW JULIE
UPADHYAYA ABHA

Interpretive Summary:
Sustainable agricultural practices will maintain soils as valuable natural resources. Well-aggregated soil structure is a major factor controlling the complex combination of physical, chemical, and biological processes that comprise soil ecosystem function. The discovery of a stable, insoluble, abundant glycoprotein deposited in soil by a group of ubiquitous root-associated fungi lead to the hypothesis that this protein was involved in soil aggregate stability. A chronosequence of prairie restorations was studied to determine the relationship between the protein, glomalin, and measures of aggregate size and stability. The results show that glomalin is the long-sought-after link between a healthy population of root-associated fungi (arbuscular mycorrhizal fungi) and soil aggregate stability. The goal of this work is to be able to enhance the quantity and stability of aggregates by managing the group of fungi that produce glomalin. The impact of this will be world-wide in scope and will extend to future generations.
Keywords:
soil rhizosphere ecology biology quality productivity fertility indicators transition long term sustainable agriculture study sites microbial diversity community structure biomass siderophores iron nutrient competition phospholipid fatty acid methyl ester biochemical activity characteristics
Contact:
10300 BALTIMORE BLVD.
RM 108, BG 318, BARC-EAST
BELTSVILLE
MD 20705
FAX: 301 504-8370
Email: SWRIGHT@ASRR.ARSUSDA.GOV
Approved Date: 1996-08-30

TEKTRAN
United States Department of Agriculture
Agricultural Research Service

Updated: 1998-12-18
FUNCTIONAL SIGNIFICANCE OF GLOMALIN TO SOIL FERTILITYIn the U.S., soil is lost to wind and water erosion at a rate of nearly 2 billion tons yr-1. The formation of aggregates helps stabilize soil and increase soil fertility. Organic matter concentration is correlated with the percentage of water-stable aggregates (WSA). The hypothesis of this study was that glomalin, a glycoproteinaceous substance produced by arbuscular mycorrhizal fungi, would be a major fraction of organic carbon in WSA. Four organic matter fractions – particulate organic matter (POM), total glomalin, humic acid (HA) and humin – were quantified in 1-2 mm dry-sieved aggregates from two native eastern Colorado grassland soils – Sampson and Haxtun. Each fraction, except for humin which remained in the soil after all extractions, was sequentially extracted from the same aggregate sample. Extraction procedures separated total glomalin into three different fractions: glomalin associated with POM (POM-glomalin), initial glomalin extracted from POM-free soil (glomalin), and recalcitrant glomalin (R-glomalin) extracted from POM-free soil after all other fractions. After extraction of glomalin, the POM fraction was reclassified as residual POM (R-POM). The WSA percentage was measured by wet-sieving. In this study, WSA percentage was 52% for the Sampson soil and 62% in the Haxtun soil. In the Sampson soil, the amount of carbon in the total glomalin and R-POM fractions were almost equivalent and greater than in the humin and humic acid fractions. In the Haxtun soil, the humin fraction accounted for the majority of carbon followed closely by R-POM and total glomalin. The Haxtun soil was a sandy loam with less R-POM and total glomalin, especially R-glomalin, than in the Sampson loam. The R-POM fraction contains many labile polysaccharides to help glue aggregates together as well as roots and fungal hyphae to provide the framework for aggregate formation. Glomalin also contains polysaccharides to glue aggregates together as well as iron to form stable bridges with clay minerals and hydrophobic groups such as aliphatic amino acids. The organo-mineral complexes formed between clay minerals and glomalin or humin and a hydrophobic coating from glomalin help keep aggregates water-stable and protected from water and wind erosion.

Newsgroups: rec.arts.bonsai Date: 2003-06-02 14:50:14 PST
Theo: Are you sure the article was about glucose and not glomalin? I will copy below parts of an article I published in my March 2003 newsletter. The original article was from the September 2002 issue of Agricultural Research magazine.
Until its discovery in 1996 this soil "super glue" was mistaken for an
unidentifiable constituent of soil organic matter. Rather, it permeates organic matter, binding it to silt, sand, and clay particles. Not only does glomalin contain 30 to 40 percent carbon, but it also forms clumps of soil granules called aggregates. These add structure to soil and keep other stored soil carbon from escaping.
As a glycoprotein, glomalin stores carbon in both its protein and
carbohydrate (glucose or sugar) subunits. Dr. Sarah Wright, who discovered this substance, thinks the glomalin molecule is a clump of small glycoproteins with iron and other ions attached. She found that glomalin contains from 1 to 9 percent tightly bound iron.
Glomalin is causing a complete reexamination of what makes up soil organic matter. A study showed that glomalin accounts for 27 percent of the carbon in soil and is a major component of soil organic matter. Glomalin weighs 2 to 24 times more than humic acid, a product of decaying plants that up to now was thought to be the main contributor to soil carbon. But humic acid contributes only about 8 percent of the carbon. Another team recently used carbon dating to estimate that glomalin lasts 7 to 42 years, depending on conditions.
Interestingly, the article noted that a current study in Costa Rica uses glomalin levels and root growth to measure the amount of carbon stored in soils beneath tropical forests. Researchers are finding lower levels of glomalin than expected and a much shorter lifespan. "We think it's because of the higher temperatures and moisture in tropical soils." These factors break down glomalin.(To me, this means that the extra heat our soils endure in our containerized bonsai might cause the same effects.)
It is glomalin that gives soil its tilth—a subtle texture that enables
experienced farmers and gardeners to judge great soil by feeling the smooth granules as they flow through their fingers.
Arbuscular mycorrhizal fungi, found living on plant roots around the world, appear to be the only producers of glomalin. Glomalin was named after Glomales, the taxonomic order that arbuscular mycorrhizal fungi belong to. The fungi use carbon from the plant to grow and make glomalin. In return, the fungi's hairlike filaments, called hyphae, extend the reach of plant roots. Hyphae function as pipes to funnel more water and nutrients—particularly phosphorus—to the plants.
"We've seen glomalin on the outside of the hyphae, and we believe this is how the hyphae seal themselves so they can carry water and nutrients. It may also be what gives them the rigidity they need to span the air spaces between soil particles."
As a plant grows, the fungi move down the root and form new hyphae to
colonize the growing roots. When hyphae higher up on the roots stop transporting nutrients, their protective glomalin sloughs off into the soil. There it attaches to particles of minerals (sand, silt, and clay) and organic matter, forming clumps. This type of soil structure is stable enough to resist wind and water erosion, but porous enough to let air, water, and roots move through it. It also harbors more beneficial microbes, holds more water, and helps the soil surface resist crusting.
Scientists think hyphae have a lifespan of days to weeks. The much longer lifespan of glomalin suggests that the current technique of weighing hyphae samples to estimate fungal carbon storage grossly underestimates the amount of soil carbon stored. In fact, Wright and colleagues found that glomalin contributes much more nitrogen and carbon to the soil than do hyphae or other soil microbes.
There was much more to the article, but the list limits length of responses,
so that will do for now.
Alan Walker, Lake Charles, LA, USA

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Theo wrote:
HI
In the italian Issue of Bonsai and news is published a topic about
the use of glucose to enhance the roots growth. I do not know what it deals
exactly about. any feed back from others review / personal experience?
Theo