Abstract
BackgroundHydroponic systems are a convenient platform for plant cultivation when treatments are applied to the roots because they provide precise control of the composition of the growth medium, ensuring the availability of different compounds. A problem arises when axenic conditions are needed but the treatment of choice (exogenous organic acids or sugars) promote the growth of unwanted microorganisms. Moreover, axenic conditions are usually applied in liquid and semi-liquid growing systems, where oxygen availability can be compromised, if no aeration is provided.ResultsThe driver for the development of this hydroponic system was the application of the organic acid pyruvate to the roots of plants grown under aerated axenic conditions. No contamination was detected in the nutrient solution, even after the addition of pyruvate. The system was validated in pea plants treated with either pyruvate or herbicides inhibiting amino acid biosynthesis. The effects on ethanol fermentation were compared by analysing the enzymatic activity, protein content and transcriptional levels in plants treated with either pyruvate or herbicides.ConclusionsThe developed system enables the study of the exogenous application of organic acids in the nutrient solution under axenic conditions and without oxygen limitation. This system allows the study of the effect of any type of treatments applied to roots under aerated axenic hydroponic systems at physiological and molecular levels. The role of pyruvate in the induction of fermentation by herbicides cannot be simply explained by an increase in substrate availability.
Highlights
Hydroponic systems are a convenient platform for plant cultivation when treatments are applied to the roots because they provide precise control of the composition of the growth medium, ensuring the availability of different compounds
To confirm that no microorganisms were present in the nutrient solution, the presence of fungi, bacteria and yeast was tested by the cultivation of nutrient solution samples on potato dextrose agar (PDA) and L broth media (LB) agar plates at different temperatures (Fig. 2)
To ensure that axenic conditions were maintained after the application of the different treatments, the presence of fungi, bacteria and yeast was tested by culturing nutrient solution samples on PDA and LB plates, two generic growth media used for the cultivation of microorganisms
Summary
Hydroponic systems are a convenient platform for plant cultivation when treatments are applied to the roots because they provide precise control of the composition of the growth medium, ensuring the availability of different compounds. Hydroponic systems are of particular interest when treatments are applied to the roots because they provide precise control of the composition of the growth medium, facilitating the management of different compounds in the medium [3,4,5,6] The problem with these systems is that they are not efficient for the application. A hydroponic system without aeration for aseptic conditions was developed for Arabidopsis [3], and more recently, an improved axenic system for the rapid production of roots has been described [8] The latter consists of a system with a unique air source to which all the individual boxes containing the plants are connected; it is a good system for the rapid growth of roots, the system does not handle the application of treatments in the nutrient solution. Expanded clay balls were used to anchor the seedlings [8], which can interfere with applied treatments by adsorption of organic molecules due to the surface of clay particles
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