Actinorhiza
Definitions
An actinorhiza is referred to as a root nodule formed as a result of a symbiotic relationship between an actinomycete and fine plant roots. [1] To further clarify what an actinorhiza is, refer to the following:
Root Nodule: A small knot or joint on a stem or root, especially one containing nitrogen-fixing bacteria [1]
Symbiotic: A relationship with mutual benefit between two individuals or organisms [1]
Actinomycete: Any of various bacteria (order Actinomycetales) with a branching, filamentous structure [1]
Root Nodules
As stated above, actinorhiza are the small nodules that form on the roots of plants. These nodules produce tangible nitrogen for the plants that they are attached to by pulling in nitrogen that is currently in the atmosphere. These nodules are essential to plant growth, as plants struggle to find sources of nitrogen without them, making it difficult for them to grow and stay alive. However, root nodules are not able to form on every kind of plant. The type of plant that can host the nodules consist mainly of legumes. Other types of plants must rely on other sources of nitrogen, which for crops and other plants grown by farmers, comes from fertilizer. A study done by Horst Rohrig and Richard Walden shows that nodules can be artificially grown on non-leguminous plants. The us of lipo-chitooligosaccharides, or LCOs, shows that non-leguminous plants can undergo the same type of cell division to create nodules on their roots. Although these nodules do not have the same nitrogen fixation ability as the naturally occurring nodules, this study does show that LCOs are a main factor of plant and root nodule growth. [2]
Frankia
Frankia is a type of actinomycete that forms a symbiotic relationship with plant roots in order to form actinorhiza for nitrogen fixation. To form these symbiotic relationships, the Frankia strain sends out hyphae, which burrow into the roots and reside inbetween the cell wall structures of the plant cells. [4]
Citations
[1] "actinorhiza." YourDictionary, n.d. Web. 4 April 2018. <http://www.yourdictionary.com/actinorhiza>.
[2] Adler, Tina. "Getting to the root of nodule formation." Science News, 12 Aug. 1995, p. 102. General OneFile, http://link.galegroup.com/apps/doc/A17198831/GPS?u=avlr&sid=GPS&xid=b3e076c8. Accessed 5 Apr. 2018.
[3] Taylor, Ariel. “Assimilation and Fixation of Nitrogen.” SlidePlayer, Slideplayer.com Inc., 2016, slideplayer.com/slide/7611776/.
[4] Benson, David R., and Warwick B. Silvester. "Biology of Frankia strains, actinomycete symbionts of actinorhizal plants." Microbiological Reviews, vol. 57, no. 2, 1993, p. 293+. General OneFile, http://link.galegroup.com/apps/doc/A14217442/GPS?u=avlr&sid=GPS&xid=c8cc6110. Accessed 7 Apr. 2018.