Biotic: Fungi
The Kingdom Fungi is very resistant to changes in the environment. They are
highly adaptive and can survive environmental conditions that most other
eukaryote life-forms could not withstand. Their method of propagation uses
spores, which spread widely and are relatively unselective in where they root.
The body, called mycelium, of fungi is made of threads called hyphae. Hyphae
absorb nutrients from the substrate, spread, grow, and produce fruiting bodies.
These bodies are the visible parts of the fungus. Fungi are unable to produce
their own food. They obtain their food from dead organic matter, or from living
organisms. The functions of fungi are highly diverse and have many implications
for science and the health of the rainforest.
There are three types of symbiosis: parasitic, mutual, and neutral. Parasitic
relationships benefit the fungus, but harm the host. This type of relationship
is often observed as a problem for agriculture. Neutral relationships benefit
the fungi without harming the host
A mutual relationship is beneficial for both the fungus and the host. Two
types of Mycorrhizal mutual symbioses are seen in the soil of the Amazon:
ectomycorrhizae and endomycorrhizae. Both are methods of aiding plant ion
absorption, the difference being ectomycorrhizal fungi only coat the root
system, while endomycorrhizal fungi invade the primary cortex of the root
system, though still leaving the main roots and secondary cortex intact. This
symbiotic relationship effectively increases the active surface area of the
plant roots by as much as a factor of ten. These fungi supply the plants with P,
N, and K in a usable form, as well as limit pathogen entry through the roots.
This results in increased water regulation, allowing for a more rapid recovery
from droughts and a biotic stresses. In exchange, these plants provide the fungi
with sugars produced through photosynthesis. Recently, a study done in Venezuela
suggests that mycorrhizae inoculation could be used to aid in rehabilitation of
deforested soils. The experimenters attempted two methods of treatments (as well
as controls). One involved phosphorus fertilizers and mycorrhizal inoculation (I+P)
while the other was only inoculation with mycorrhizal fungi (I). The (I+P)
treatment caused a 60% increase in above ground biomass after a five month
re-growth period as compared to a control, and twenty times that of the (I)
treatment. The chemical analysis of these soils showed that while no
exchangeable P was detected in the controls, there was about 2.17 mg/g in
inoculated and fertilized soils. The researchers believe that this is because in
general, plants in mature tropical ecosystems depend on presence of mycorrhizae
for their development. Therefore, when disturbance, such as deforestation,
causes a loss of mycorrhizae, "recovery of the degraded areas is only possible
if these propagules are reintroduced by natural processes or human
intervention".
Human interests in fungi include numerous drugs (such as penicillin and other
antibiotics), foods like mushrooms, truffles and morels, and yeast, which
provides the bubbles in bread, champagne, and beer.
Next: Epiphytes->