Effect of monopotassium phosphate levels on the amino acids profiles in sunflower root exudates (in vitro obtaining) and its effects on chemotactic behavior of microorganisms PAHs degrading.

The exudation of nutrients by the roots of plants is one of the main mechanisms described for bioremediation of soils contaminated with polycyclic aromatic hydrocarbons (PAHs). Exudates facilitate the proliferation of soil microorganisms active in the degradation of these organic compounds. Sunflower (Helianthus annus) is considered a feasible species for PAHs elimination in polluted soils because it has good seed germination and develops depth and profuse radical system in these contaminated soils. Sunflower root exudates in vitro obtained and characterized later have a positive effect on PAHs elimination. Readily degradable compounds such as amino acids found in root exudates have been postulated to be part of a fast pool of carbon which is rapidly utilized and cycled through the microbial cells. It¿s known that reduction of phosphorous and potassium enhances amino acids production by roots. In consequence, in this work reductions of monopotassium phosphate to 25 and 50%, in the MM medium in in vitro culture were assayed. The obtained results indicate that the main wealth, both in number (12) and concentration (6.29 mgL-1) of amino acids were reached at the minor monopotassium phosphate level (25%) foregrounding significantly the histidine and arginine levels. The highest amino acid content found in this exudate with 25% of monopotassium phosphate leads a high chemotactic index in Pseudomonas putida G7, bacteria able to degrade naphthalene. In consequence, the reduction of monopotassium phosphate to a quarter in the substract can have a clear positive effect on the bioremediation action in the degradation of PAHs in contaminated soils.

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