Post by Ask Jan on Nov 3, 2011 13:18:01 GMT -8
MYCORRHIZAE—The Benefits Of. . . . . Fungus Roots
About one hundred and twenty years ago, scientists discovered that some fungi invaded plant roots without causing diseases. We now recognize this strange mould (mold)-plant relationship as symbiotic not parasitic.
Zygomycetes--a subclass of fungus
Saprophytic--a plant living on dead or decaying organic material, obtaining nourishment osmotically.
Symbiotic—the living together of two dissimilar organisms to a mutually beneficial relationship.
Synergistic—combined action, working together, an agent that increases the effectiveness of another agent when combined with it.
Mycorrhizae-- Latin for fungus roots
Mycology—branch of botany dealing with fungi
Parasitic--living in/on another living organism.
These associations occur in almost all plants and are very important. Mycorrhizae nevertheless have escaped wide attention, because infected roots look normal and the fungi themselves grow with difficulty in artificial culture.
Mycologists describe two classes of mycorrhizae. Ectomycorrhizae associated with tree species (especially gymnosperms) and Endomycorrhizae associated with trees and herbaceous plants. Endomycorrhizae produce swellings (vesicles) or minute branches (arbuscules) within plant cells. Botanists call them VA mycorrhizae.
Recently notes and photographs taken of Cannabis roots by Arzberger (1925) were rediscovered in the USDA archives. In 1961, Mosse produced an artificial VA mycorrhizae relationship in cannabis by inoculating roots with an “Endogone species”. In 1997, McPartland & Cubeta documented naturally occurring VA mycorrhizae in feral hemp. They identified the fungus as a Glomus species, probably Glomus mosseae.
In 1954, Merlin & Rama Das discovered that metabolites produced by Cannabis roots enhance the growth of mycorrhizal fungi. In return, mycorrhizal fungi improve cannabis growth by increasing the surface area of the root network and making several soil nutrients more available. Some nutrients are immobile in soil, which causes a nutrient depletion zone to form around roots. Mycorrhizal fungi grow beyond the root zone and draw nutrients back to the plant.
Phosphate ions are the most immobile soil nutrients. In 1983, Menge found that mycorrhizae infected plants absorb sixty times more phosphorus than uninfected plants. Uptake of zinc and copper dramatically increases and absorption of potassium, calcium, iron, magnesium, manganese and sulfur also improves. Only the absorption of nitrogen (most mobile nutrient) remains unchanged in the presence of mycorrhizae. Nitrogen fixing Azotobacter species, however, synergistically increase plant growth when inoculated with mycorrhizal fungi.
The mycorrhizal mantle protects plants from some root-feeding insects, nematodes, and many fungal pathogens. Mycorrhizae also aid plants by reducing drought stress, and even produce plant growth hormones.
Mycorrhizal fungi serve as “biotic fertilizers”, substituting for nutrient supplements. Optimizing the growth of mycorrhizal fungi requires a balance of proper pH, moisture, light intensity, soil fertility, percentage of organic matter, and soil flora and fauna—not a project for the novice grower!
In 1982 Hayman described two pointers for beginners: adding organic fertilizers to soil improves mycorrhizal growth, whereas adding petrochemical fertilizers (ammonium nitrate) decreases mycorrhizal growth.
Almost all soils contain natural populations of mycorrhizal fungi. Exceptions include soils laying fallow for two or more years, and soils supporting continuous crops of non-mycorrhizal plants (broccoli, cabbage, cauliflower, turnips, mustard greens) and weeds (quinoa, lamb’s quarters, pigweed). Plastic sacks of sterile potting soil, peat moss, builder’s sand, and perlite also lack mycorrhizae.
You can inoculate sterile soil by adding mycorrhizal fungi. Adding a handful of “starter”—soil and root fragments from a previously successful crop. Plants grown in soil inoculated with pure spores were two hundred times greater than plants grown in sterile soil. You can disinfect your spores using streptomycin and sodium hypochlorite (bleach) to get a pure inoculum. The mycorrhizal fungus Glomus intraradices is now commercially available as a biocontrol against Pythium and Fusarium species.
Some hydroponic systems operators inoculate their systems with mycorrhizae to optimize nutrient uptake.
Hemp Diseases and Pests, J. M. McPartland, R. C. Clarke and D. P. Watson, 2002 Reprint