grnknight

Spent a couple of hours surfing around for information about soil microbiology
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SOME RESEARCH INTO SOIL MICROBIOLOGY

VOCABULARY
Adventitious roots:
http://www.botgard.ucla.edu/html/bot.../typesofroots/
"Adventitious roots are the ones that form from shoot tissues, not from another (parent) root."

seminal roots:
http://www.ffp.csiro.au/research/mycorrhiza/root.html
"Seminal root - from a seed "

hyphae:
http://www.answers.com/hyphae&r=67
The long, branching filaments of which the mycelium (and the greater part of the plant) of a fungus is formed. They are also found enveloping the gonidia of lichens, making up a large part of their structure.

arbuscles:
http://www.ffp.csiro.au/research/mycorrhiza/VAM.html
Arbuscules are intricately branched haustoria that formed within a root cortex cell. They were named by Gallaud (1905), because they look like little trees.

RESOURCES
http://www.cias.wisc.edu/wicst/pubs/...lstructure.htm
- 0.25-7-8mm is the ideal size of aggregate for root development
-disease tends to start at tips of seminal or adventitious root and work up

http://www.ffp.csiro.au/research/mycorrhiza/root.html
- Young roots with living epidermal cells and root hairs, are often considered to be responsible for most direct nutrient uptake (Marschner 1986). Mycorrhizal formation by both ECM and VAM fungi requires actively growing, or recently formed roots.

http://www.ffp.csiro.au/research/mycorrhiza/VAM.html
- VAM associations involve fungi in the Zygomycete order Glomales and the roots of a wide diversity of plants.
- Hyphae resulting from spore germination have a limited capacity to grow and will die if they do not encounter a susceptible root within a week or so.
- The network of hyphae in the soil is only connected to roots by the entry points that initiate mycorrhizal associations, as hyphae do not grow out of living roots.
- Mycorrhizal associations start when soil hyphae respond to the presence of a root by growing towards it, establishing contact and growing along its surface. Next, one or more hyphae produce swellings called appressoria between epidermal cells. Root penetration occurs when hyphae from the appressoria penetrate epidermal or cortical cells to enter the root. These hyphae cross the hypodermis (through passage cells if these are present in an exodermis) and start branching in the outer cortex.
- In roots with Arum series associations, VAM hyphae proliferate in the cortex by growing longitudinally between host cells. This occurs because hyphae grow through longitudinal intercellular air spaces that are present (Brundrett et al. 1985).
- In Paris series VAM hyphae spread by forming coils within cells because there are no continuous longitudinal air spaces.
]] what type is cannabis? need to look closer at root morphology[[
- Arbuscules start to form approximately 2 days after root penetration.
- Arbuscule formation follows hyphal growth, progressing outwards from the entry point. Arbuscules are short-loved and begin to collapse after a few days, but hyphae and vesicles can remain in roots for months or years.
- Vesicles are initiated soon after the first arbuscules, but continue to develop when the arbuscules senesce. Vesicles are hyphal swellings in the root cortex that contain lipids and cytoplasm. These may be inter- or intracellular. Vesicles can develop thick walls in older roots and may function as propagules (Biermann & Linderman 1983).
- Spores form as swellings on one or more subtending hypha in the soil or in roots.
- Spores may be aggregated into groups called sporocarps. Sporocarps may contain specialised hyphae and can be encased in an outer layer (peridium). Spores apparently form when nutrients are remobilised from roots where associations are senescing. They function as storage structures, resting stages and propagules.

http://www.ffp.csiro.au/research/mycorrhiza/ecm.html
- Ectomycorrhizal roots (which have also been called ectotrophic associations or sheathing mycorrhizas) are characterised by the presence of a mantle and Hartig net, but both these structures may not be well developed. Detailed descriptions of ECM root morphology have been published elsewhere (eg. Kottke & Oberwinkler 1986, Massicotte et al. 1987).
- Ectomycorrhizal associations are formed predominantly on the fine root tips of the host, which are unevenly distributed throughout the soil profile, being more abundant in topsoil layers containing humus, than in underlying layers of mineral soil (Meyer 1973, Harvey et al. 1976).
- Most plants with ECM have roots with a modified lateral root branching pattern. This pattern, which is called heterorhizy, consists of short mycorrhizal lateral roots (called short roots) supported by a network of long roots.
- The restricted growth of short roots may be necessary to allow ECM fungi time to form an association, since these fungi have difficulty colonising more rapidly growing roots (Chilvers & Gust 1982).
- Hyphae contact, recognise and adhere to root epidermal cells near the apex of young, actively growing, high-order, lateral root. These are called short roots because they normally have limited longitudinal growth.
- The size, colour, texture and branching patterns of ECM roots vary with different host-fungus combinations.
- Hyphae penetrate between host cells and branch to form a labyrinthine structure called the Hartig net. Host responses may include polyphenol production in cells, phenylpropanoid accumulation and the deposition of secondary metabolites in walls (Weiss et al. 1997, Ling-Lee et al. 1977, Brundrett et al. 1990).
- The active mycorrhizal zone occurs several mm behind the root tip (as a result of the time required for mycorrhizal formation), but Hartig net hyphae senesce (as indicated by ultrastructural changes) in older regions further from the root tip (Massicotte et al. 1987). Consequently, Hartig net activity depends on root age and root growth. The mantle in older roots generally persists long after associations become inactive. Older ECM roots probably function as storage structures and propagules.
- The majority of ECM hosts are trees, or shrubs (see Table), but associations are formed by a few herbaceous plants, including Kobresia (Cyperaceae), Polygonum (polygonaceae) and Cassiope (Ericaceae) species found in alpine/arctic regions (Kohn & Stasovski 1990, Massicotte et al. 1998).
- Surveys of the mycorrhizal literature have established that plants within a genus usually have the same type of mycorrhizas (ECM, VAM, etc. or remain nonmycorrhizal) and these relationships are generally also consistent within a family (Harley & Harley 1987, Newman & Reddell 1987, Brundrett & Abbott 1991).

http://www.gchydro.com/art_mycorr.asp
"Copyright Notice
This material appeared in slightly modified form in Mushroom: the Journal of Wild Mushrooming, Issue 69, Fall 2000. It can be used freely for not-for-profit personal and educational purposes provided that its source is clearly credited. "
- Ectomycorrhizas ("outside" mycorrhizas) are the easiest type to recognize in the field, being discernible with the unaided eye. Their name comes from the fact that they have an often well developed periradical phase (called the mantle or sheath), present as a thin-to-thick mass of hyphae that covers the outside of the fine root tips and provides a characteristic appearance (Figure 3). Abundant hyphae emanate from the mantle into the surrounding soil to form the extraradical phase
- Endomycorrhizas ("inside" mycorrhizas) do not form a mantle around the root, so have no periradical phase. They have an often well developed extraradical phase, as a typical mycelial network permeating the soil. The fungi do not form complex sporocarps, instead reproducing by means of large spores that remain in the soil and are moved around with it.
- As you read the literature on mycorrhizas, you undoubtedly will encounter all three terms -- endomycorrhiza, vesicular-arbuscular mycorrhiza, and arbuscular mycorrhiza. In general, you can consider them to be equivalent.
- Thus, mycorrhizas are thought to occur in at least some members of nearly all plant families and at least 80-90% of higher plant species. Arbuscular mycorrhizas also occur in so-called lower plants such as whisk fern (Psilotum nudum), ground pines (Lycopodium spp.), mosses, liverworts, and ferns.
- Overall, only a relatively small number of species appears to be non-mycotrophic. These tend to be mostly weedy species in families such as the Brassicaceae (mustards), Cyperaceae (sedges), and Chenopodiaceae (spinach, lamb's quarters).
- From a plant's perspective, the major role of most mycorrhizas is to provide access to water, growth-limiting nutrients, or carbon at critical times in its development.
- Arbuscular mycorrhiza is the dominant type in the tropics, and in grasslands and deserts of temperate latitudes. Ectomycorrhizas predominate in temperate and boreal forests. In even higher latitude areas, the ericoid mycorrhizas flourish in heathlands. Although this broad pattern does exist, remember that it masks much underlying complexity and that many areas support mixtures of the different mycorrhiza types.

http://www.hort.wisc.edu/mastergarde...mycorrhiza.htm
- Ectomycorrhizae not only absorb phosphate from the soil but they also are important in ammonium and zinc uptake as well. The fungi that form a symbiotic relationship with the plant are relatively host-specific. However, some fungal species may be more generalized and will colonize several species of plants.
- Vesiculararbuscular endomycorrhiza (V-A type) are the type commonly found on deciduous trees as well as annual agronomic crops and other herbaceous plants.

http://www.google.com/search?q=cache...tivation&hl=en
After 4-months culture, AM fungal inoculation significantly increased the plant biomasses (by 1.78! and 2.23! for shoot and root biomasses, respectively), while mineral phosphate amendment had no effect in a sterilized soil. After 12-months culture, the biomasses of
A. holosericea plants growing in a non-sterilized soil amended with mineral phosphate were significantly higher than those recorded in the control treatment (by 2.5! and 5! for shoot and root biomasses, respectively). The fungal inoculation also significantly stimulated plant growth, which was significantly higher than that measured in the mineral phosphate treatment. When G. intraradices and mineral phosphate were added together to the soil, shoot growth were significantly stimulated over the single treatments (inoculation or amendment) (1.45!).The P leaf mineral content was also higher in the G. intraradicesCmineral phosphate treatment than in G. intraradices or rock phosphate
amendment. Moreover, the number of fluorescent pseudomonads has been significantly increased when G. intraradices and/or mineral phosphate were added to the soil. By using a specific type of multivariate analysis (co-inertia analysis), it has been shown that plant growth was positively correlated to the metabolization of ketoglutaric acid, and negatively linked to the metabolisation of phenylalanine and other substrates, which shows that microbial activity is also affected.
++NOTE++
A. holosericea is in the same class as hemp - magnoliophyta, but diverges into the family rosidae
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http://mycorrhiza.ag.utk.edu/realmycr.htm
- In exchange for possible positive effects on host plant growth, the fungus takes from the plant the carbon compounds (food) it requires. It has been estimated that approximately 10 to 25 percent of the carbohydrates made by the plant's foliage ultimately wind up nourishing the mycorrhizae. In some instances, particularly during the fungal establishment phase in young seedlings or cuttings, growth of mycorrhizal plants may lag slightly behind that of plants which do not have to "feed" a fungal partner. This reduction of growth by mycorrhizal fungi does not always occur, however, and is usually short-lived when it does occur. Growth of mycorrhizal plants in phosphorus-deficient media typically rapidly matches and then usually greatly exceeds that of nonmycorrhizal plants.
- For many, if not most crops, the amount of phosphorus applied to plants must be limited to about one-third to one-tenth of that normally applied. Higher rates of phosphorus often discourage colonization of the fungi.

http://mycorrhiza.ag.utk.edu/latest/1994/94_sande1.htm
- Significantly higher concentrations of phosphorus in mature reproductive parts of both mycotrophic species in treatments where mycorrhizal fungi were present suggest that the mycorrhizal symbiosis could significantly affect the quality of seed and may have long-term effects on the structure of plant communities.

http://www.ias.ac.in/currsci/nov25/articles26.htm
- Thus, mycorrhizal S. aculeata plants, under low P supply absorb more P than non-mycorrhizal plants due to a metabolically-dependent higher P influx. A Langmuir type kinetic equation could adequately describe time dependent uptake kinetic of P in the plant species. Phosphorus accumulation in mycorrhizal roots occurs through a metabolically-dependent process, however, translocation of absorbed P to stem and leaves is much less dependent on this component.

http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract
- 150 rhizospheric soil samples were collected from 45 wild plants distributed in Shandong Province during 1995-1997. More than forty species of AM fungi were isolated, and the effects of some soil factors on AM fungi were also investigated. It was proved that soil conditions were important factors to the colonization, growth, and distribution of AM fungi. Spore numbers were highest in brown earth, and lowest in alkali-saline soil. Glomus occurred in all types of soil. The occurrence frequency of Gigaspora and Scutellospora was much higher in brown earth. The distribution of AM fungi was also affected by soil pH. Glomus occurred in soil with a wide pH range. The greater of soil alkalinity, the more Glomus were found, while the greater of soil acidity, the more Acaulospora were isolated. Scutellospora occurred mostly in soil with pH of 6.0-7.0, and Gigaspora distributed mainly in acid soi

http://www.ces.purdue.edu/extmedia/FNR/FNR-104.html
- High light intensities and low to moderate soil fertility enhance mycorrhizal development, while the opposite conditions may reduce or even prevent mycorrhizal development. These factors may influence the biochemical status of the root by controlling the level of reducing sugars, or they may affect the synthesis of new (susceptible) feeder roots (Figure 5).
- When high concentrations of readily available nitrogen and phosphorous are absorbed from soils and translocated upward to the growing portions of the plant, soluble carbohydrates are assimilated rapidly during formation of new tissue in the shoot. Consequently, the quantity of soluble carbohydrates translocated to and accumulated in the roots is low.
- Optimum temperatures for mycelial growth lie between 18C and 27C for the majority of fungal species. Such ectomycorrhizal fungi as Pisolithus tinctorius which develop at soil temperatures of 34C or higher, offer advantages in reforestation of adverse sites.
- Apparently all mycorrhizal fungi require oxygen to survive. It is generally conceded that formation of ectomycorrhizae on tree roots is greatest under acid conditions.


http://mycorrhiza.ag.utk.edu/
the mycorrhiza exchange site, lots of research papers