Resumo

MOLINA L, Mauricio; MEDINA S, Marisol  e  OROZCO P, Hernando. The effects of the interaction Frankia - mycorrhizal fungi - microelements in the establishment of Alder trees (Alnus acuminata) in tree grass systems. Rev Colom Cienc Pecua [online]. 2006, vol.19, n.1, pp.39-48. ISSN 0120-0690.

Frankia is a genus of microorganisms called actinomycetes able to induce the formation of radicular nodules that fix atmospheric nitrogen in some non-legumes angiosperms, denominated actinorrhizal plants. The development of symbiotic fixing of N envolves multiple processes that are carried out in endosimbiotic subcellular compartments in which Frankia produces the nodules of the root which turn the N₂ in combined form. The mycorrhizal symbiosis and the nodules are generally synergistic. They promote the vegetal growth, the multiplication of mycorrhizae producing a more competitive atmosphere for the pathogens. It is important to consider the participation of micronutrients like molibdenum, which is a component of the nitrogenase, since its deficiency in the medium causes a direct and negative effect in the fixing of the N₂. The boron deficiency produces a destabilization of the protecting cover against oxygen, which considerably affects the nodulation of the plant. Cobalt is a structural component of the coenzyme of the B12 vitamin in the process of the fixing of the N. Nevertheless, many aspects related to these micronutrients in the interactions and the mycorrhizal-Frankia symbiosis is unknown. It is important to determine the effects on the microorganisms and the development of the nodules; for determining an optimum development, however its complexity makes its effect to be unpredictable under all conditions and for all species. Therefore, it is important to stimulate the investigation on the matter, as well as to research on more information on the principles of the functioning, interactions, and show results found on the use of promissory trees for tree grass systems in high tropic as the Aliso (Alnus acuminata), a forestal species useful for solving the degradation problems of the soil and deforestation.

Palavras-chave : boron; cobalt; molibdenum; fixing of N₂; actinorrhizal plants; symbiosis.

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