The advantages of growing plants using hydroponics have been widely recognized in the production of large and uniform plants, enabling reproducible experiments1,2,3. In this system, the composition of the nutritive solution can be properly controlled and recycled along all stages of plant growth and development. Furthermore, roots are not subjected to abiotic stresses, as can happen in soil-grown plants, such as nutrient starvation and water deficiency4. As plants grown hydroponically present morphological and physiological traits fairly similar to the ones cultured in soil, this system has been broadly employed in research because it allows the monitoring of root/shoot growth and their harvesting without injuries2,5.
Due to the possibility of changing the composition and concentration of the nutritive solution, most of the research using hydroponic conditions has been performed to characterize the functions of micro- and macronutrients1,3,6,7,8. However, this system has proved to be very useful to a broad range of applications in plant biology, such as to elucidate the functions of hormones and chemicals in plants. For instance, the discovery of strigolactones as a new class of hormones9 and the accelerated growth phenotype triggered by brassinosteroid application10 were performed under hydroponic conditions. Moreover, this system enables experiments with labeled isotopes (e.g., 14N/15N and 13CO2)11,12 to evaluate their incorporation into proteins and metabolites by mass spectrometry.
Considering the importance of this system in plant research, a high number of hydroponic cultures has been designed in the last few years, including systems that use (i) the transference of seedlings from plates to hydroponic containers3,13; (ii) rockwool that limits access to the early stages of root development2,14,15; (iii) polyethylene granulate as the floating body, which makes the homogeneous application of small molecules/treatments difficult16; or (iv) a reduced number of plants9,17. The volume of hydroponic tanks described in many of those protocols are usually large (small volumes ranging from 1 - 5 L, up to 32 L)18, which makes the application of chemicals extremely expensive. Although few studies do describe a hydroponic cultivation under aseptic conditions8,19, the assembly of the system is usually quite laborious, consisting of the perfect adjustment of nylon meshes into plastic or glass containers5,8,17,20.
Due to the importance of Arabidopsis thaliana as a model plant, the majority of hydroponics systems were designed for this species1,2,8,14,18,19,20. Nevertheless, there are a few studies reporting the hydroponic growth features of other plant species with a pretreatment of seeds to improve their germination and synchronization rates in vitro8,16. In order to work on a large scale, we developed a protocol for setting up a simple and low-cost maintenance hydroponic system that enables sterile conditions for growing plants, including A. thaliana and other species, such as the grass Setaria viridis. The method described here is suitable for different experiments, as the seedling growth can be maximized, synchronized, and easily monitored. Furthermore, this system has many advantages as: (i) its assembly is straightforward and its components can be reused; (ii) it allows the easy application of different chemicals into the liquid medium; (iii) the seedlings germinate and grow directly in the culture medium without the need of transference to the hydroponics system; (iv) the shoot and root development/growth can be closely supervised and the seedlings are harvested without damages; and (v) it makes it possible to work on a large scale, maintaining physiological conditions.