For those who have seen "Avatar," the movie, you may recall the humans stationed on the fictional planet "Pandora" discovered that the vegetation there was widely interconnected through an "electrochemical" network utilizing the multitude of roots and lianas shown in many of the scenes. Additionally, the native hominoids made functional connections between themselves and their flying reptiles and horses through fine tentacles available in their respective appendages. Was this imaginary depiction of connectedness of life on "Pandora" an allusion to the connectedness of life on Earth?
I like to think so, and it's likely that many of the known aspects of the connectedness of life on Earth are not often appreciated and that many more remain to be discovered. For example, it has been known for some time that many non-symbiotic bacteria and fungi, by breaking down the tissues of dead organisms, contribute importantly to the recycling of life-sustaining nutrients. But less well known are the close physical ties that exist between most terrestrial plants and fungi. These connections involve the roots of trees and other plants and the fine mycelial threads emanating from the body or mycelium of ground-dwelling fungi. The scientific name for this functional connection between plant roots and fungi is called mycorrhizal symbiosis and the health of our forests depends greatly on it. (Those transient and colorful fleshy objects we call mushrooms or toadstools are merely the above-ground fruiting bodies of these fungi.) Thanks to their fungal partners, trees and other plants are much better supplied with water and mineral nutrients than they would otherwise be and are, therefore, healthier and more likely to survive stresses such as droughts. The fungi involved are amply repaid with vital photosynthetic products, especially sugars, produced by the plants. Additionally, some non- photosynthetic plants, such as the common Indian Pipe, are also connected into this widespread green-plant/fungus partnership, gathering both their sugars and minerals from the mycorrhizal fungus.
This connectedness between most plants and many fungi, both of which originally evolved in the sea, is hypothesized to have been a critical factor in allowing plants to emigrate out of the sea and colonize the heretofore infertile continents some 470 million years ago. Indeed the first such functional connections may have occurred between marine algae and fungi and such a symbiosis may have been the ancestor of present-day lichens which continue to demonstrate their impressive ability to colonize barren rock.
Recently we've begun to learn more about the billions of bacteria that live on and within our bodies. Some of these bacterial species make vital contributions to the digestion of our food while others are important for disease resistance. Will we be motivated to become better stewards of our environment as we learn more about the different species that make our lives possible?
Questions and suggestions from readers are welcomed and will be responded to in future editions of this column. Contact me at firstname.lastname@example.org.