Association of Microorganisms and Effect on Lettuce Seedlings Root, in Colombia

In Colombia, the diversity of soils and thermal floors, the abundance of lotic and lentic systems and the diversity of plants offer "ideal" conditions for farming. However, farmers expect to have the best profit from their investment and forget the importance of water and soil care. It is necessary that farmers learn to protect natural resources to ensure sustainable production for their families and for their community. The objective of this study was to establish the action of soil and irrigation waters`microorganisms on plant growth. Microalgae and cyanobacteria from irrigation waters and bacteria from the Bacillus genus from rhizosphere soils of various plants were isolated. Some of the genus that have been described as having plant growth promoting activity were identified. The bioassays were carried out to determine this activity toward lettuce seedlings. The results showed that the association of Chlorella sp. and Scenedesmus sp. show greater activity and they were able to promote plant growth. Bacillus bacteria were responsible for providing essential elements that benefited the plant growth promoting activity from the microalgae. Even though Bacillus bacteria are reported as excellent plant growth promoters, in these bioassays their promoting activity was lower than expected, probably due to the soil abiotic conditions. It was concluded that the biotic and abiotic factors had a major influence on rhizosphere activity lettuce seedlings used in this assay and that, regardless of origin, the microbiota of water and soil´s microbiote has an active role in the growth and development of plants. Additionally, it was observed that microorganisms from irrigation water, microalgae and cyanobacteria, have a positive effect on plant growth and production.