Agriculture Reference
In-Depth Information
Arbuscule
Figure 3.4
Example of an arbuscular mycorrhizal fungus infecting a grapevine root. The
branched fungal structure inside one of the host cells is an arbuscule through which
nutrients and carbon compounds are exchanged between the host and fungus. (Photo
preparedbyDr.MelanieWeckert,NationalWine&GrapeIndustryCentre,WaggaWagga,
Australia.) See color insert.
AMFarecommonlyfoundon
Vitis vinifera
roots and rootstocks. here are
many strains of the fungus that survive as spores in the soil when no suitable host
is present and have no preference for a particular host. However, in a perennial
plant such as
V. vinifera
, less effective strains may come to predominate over time.
Mid-rowcovercropsandweedscancounteractthistrendbymaintainingamore
diverseAMFcommunityinvineyardsoils.ColonizationbyAMFisimportantfor
newly planted vines, especially in infertile soils.
ThebeneficialeffectofAMFinenhancingPuptakeisprimarilythrough
the fungal mycelium (see table 5.1, chapter 5), which provides a pathway
for rapid P transport into the root, thereby short-circuiting the depletion
zone shown in figure 3.3. This could also be the mechanism for enhanced
uptake of other immobile elements such as Cu, Zn, and K that is some-
times observed. The mycorrhizal symbiosis is self-regulating in that, as soil
Pavailabilityincreases,theincidenceoftheinfectiondeclines.Mycorrhizal
roots live longer than non-mycorrhizal ones and have an improved capacity
to absorb water.
