Abstract
Xochimilco’s lacustrine zone is a network of channels that, along with the chinampas, conform a unique ecosystem which has served as source of aquatic resources. Duckweeds are small free-floating monocotyledon aquatic plants classified as macrophytes that serve as nutrient pumps and reduce eutrophication effects. Recently, there are number of new studies related to the aquatic plant-microbial interaction focused on the direct functional analysis that investigate plant microbe interactions at full biological hierarchy. The aim of this study was to compare the auxin in vitro production efficiency of the endophyte phytobacteria isolated from Lemna gibba L. plants collected nearby the Xochimilco aquatic agrosystem. There were 17 isolates obtained from the L. gibba plants collected in the dry season and 14 isolates for the rainy season. The environmental conditions and seasonal characteristics determined the number and identity of the isolated endophyte phytobacteria in L. gibba plants according to the several apparent differences in the water quality. This work contributes to the knowledge of the phytobacteria diversity in aquatic plants, particularly in Lemnaceae species; here the majority of the isolates have been characterized as higher indole acetic acid producers, recommended as candidates for their use as biofertilizers. Key words: Plant growth-promoting bacteria, biofertilizers, Lemna gibba , Xochimilco.
Highlights
The Xochimilco’s lake is located at the southern part of Mexico City basin and comprises a unique ecosystem which has served as source of aquatic resources, while its waters have been used for irrigation
Sharma et al (2013) mention that certain compounds produced by bacteria promote plant growth and Rajkumar and Freitas (2008) suggested that indole3-acetic acid (IAA) increase plant biomass, this effect is produced by some plant-beneficial bacteria due to their bacterial production of plant hor-mones such as indole-3acetic acid (IAA), cytokinins and gibberellins (Idris et al, 2007)
There were 17 isolates from the L. gibba plants collected in the dry season: six isolates from plants collected in urban zone, three isolates from plants collected in tourist zone and eight isolates from plants collected in chinampa zone
Summary
The Xochimilco’s lake is located at the southern part of Mexico City basin and comprises a unique ecosystem which has served as source of aquatic resources, while its waters have been used for irrigation. Duckweeds are one of the main groups considered as small (1 to 15 cm) free-floating macrophytes abundant in the Xochimilco’s lake; that serve as nutrient pumps, reducing the eutrophication effects and providing oxygen from their photosynthetic activity; these plants are often seen growing on still nutrient rich fresh and slightly brackish waters (Hasan and Chakrabarti, 2009). There were reports of some studies of Lemna and its associated bacteria that included microscopic observations and enumeration of bacteria on plant surfaces as well as several culture-dependent studies (Landolt, 1986); examples of this kind of studies are the works of Stout and Nüsslein (2005) whose compared the bacterial communities associated with the roots of L. minor plants; Yamaga et al (2010) reported the response of phenoldegrading bacteria in the rhizosphere of Lemna aoukikusa to understand their beneficial symbiotic interactions. Sharma et al (2013) mention that certain compounds produced by bacteria promote plant growth and Rajkumar and Freitas (2008) suggested that indole3-acetic acid (IAA) increase plant biomass, this effect is produced by some plant-beneficial bacteria due to their bacterial production of plant hor-mones such as indole-3acetic acid (IAA), cytokinins and gibberellins (Idris et al., 2007). Yamaga et al (2010) and Suzuki et al (2014)
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