Trees are often viewed as individuals that compete with one another for access to limited resources. But could trees in stressed environments actually benefit from positive, facultative interactions? The authors of a new paper suggest that might be the case for certain tree speciesand that it may take the form of root grafting.
Natural root grafting between individuals has been observed in over 150 species of plants around the world. However, while much is known about benefits of merging stem tissues (primarily from horticultural practices), little is known about why plants may merge, or graft, their root tissues with one another.
Emilie Tarroux and Annie DesRochers, from the Universit du Qubec in Abitibi-Tmiscamingue, Canada, were interested in determining if root grafting conferred any advantages to individual jack pine (Pinus banksiana) trees. Although the joining of tree root systems can confer advantages such as increased wind stability and sharing of resources e.g., water, photosynthates, or nutrients, Tarroux and DesRochers are the first to show how root grafting affects the growth of trees. They published their findings in the June issue of the American Journal of Botany (http://www.amjbot.org/content/98/6/967.full).
"Trees, even seed-regenerated ones like jack pine, are not independent individuals," DesRochers commented, "and may directly affect growth of their neighbors by forming root grafts."
After felling select jack pine trees in three natural stands and three plantations, Tarroux and DesRochers hydraulically excavated their root systems using a high-pressure water spray to determine if the trees had root grafts. They then aged the trees, roots, and grafts by counting and cross-dating their respective growth rings.
Interestingly, the authors found that radial growth patterns differed between jack pine trees growing naturally versus those grown in plantations. In the natural sta
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American Journal of Botany