Mycorrhizal Metal Mosh Pit

Wow, two mycorrhizal posts in a row. You would think that maybe the symbiotic relationship that is necessary for most plants to live might be important.

Populus alba branch

It should come as no surprise that in many places around the world, soils are becoming polluted. With 6 out of the 10 most highly polluted locations containing large amounts of heavy metal contamination, finding ways to deal with that particular problem are of great interest. Unfortunately, since we can't degrade heavy metals, we need to find ways to remove them from the soil.

This is where plants come in. An increasing amount of  focus has been put into a reclamation process called phytoremediation. Simply put, this is the uptake and accumulation of heavy metals into plants, which can then be removed, making for less contaminated soils. This process is more cost effective and more popular with people than machine centric traditional methods.

Typically plants used for this are small shrubs and as such are only capable of extracting an equally small amount of heavy metals, which means it takes a lot of time and replacement plants to get the job done. Recently studies have been done with larger shrubs and trees in hopes of creating a larger sink for the metals. One of the most popular trees for this is  the poplar tree.... Popular Poplar. Because of this tree's relatively quick growth and tolerance to heavy metals it is a key species for study. But, how can we make it better? How about a little arbuscular micorrhizal fungi? Namely, Glomus intraradices.

A team of Italian Scientist has just published a study, which is turn part of a larger study looking to improve phytoremediation, looking at the effects that this fungus had on leaf protein expression in the presence of heavy metals.

Effects of Heavy Metals and Arbuscular Mycorrhiza on Leaf Proteome of a Selected Poplar Clone: A Time Course Analysis

Using a clone that was previously selected because it demonstrated a natural tolerance for copper and zinc, the scientists set out to determine how much of a difference was demonstrated by presence of the fungi. The team grew their clones in a glasshouse with polluted and non-polluted soils and with or without G. intaradices inoculation. At several different intervals (4, 6, and 16 months) they took leaf samples and tested for leaf protein expression.

Their results showed that while in the short term fungal colonization caused a decrease in protein expression that outdid even that of growing the plant on polluted soils, after the initial growing season things evened out, and by the end of the 16 month period the Mycorrhizal fungi helped the poplar grow to the same extent as the tree in healthy soil. The one caveat is, even with the Fungus, leaf bio mass did not reach non-polluted soil levels.

A key lesson (besides the influence of mycorrhizal fungi on leaf protein expression) that this study demonstrates is the importance of long term and repeated sampling. If the study had only included the 4 month point sample it would appear as though the fungus had just as much of a negative effect as the poor soil, while subsequent samples illustrated quite a different and more complex tale. This observation is noted by the scientist in the study, I just wanted to add my voice.

When we do any kind of science it is always vital that we don't account a single point of data as evidence for or against a hypothesis, but that we vigorously seek to exhaust the possible variables that could change our outcomes.



Study: Guido Lingua, Elisa Bona, Valeria Todeschini, Chiara Cattaneo, Francesco Marsano, Graziella Berta, and Maria Cavaletto
Photo: Wikimedia user MPF