Background

Arabidopsis has been adopted as a model organism for a long time due to the significant features including its short life cycle, its well-annotated genome, easy transformation, and the availability of different types of mutants. Hydroponic culture has been considered as a very useful system in studying plant responses to nutrient or hormone changes since manipulation of the concentration or composition of mineral nutrients is feasible and phenotype observation of the morphology and architecture or sample collection are also convenient for diverse analyses (Hoagland and Arnon, 1941; Tocquin et al., 2003; Conn et al., 2013). However, the small size, the rosette growth habit, and the sensitivity of shoot apical meristem to flooding make the hydroponic growth of Arabidopsis difficult. Several hydroponic culture systems have been developed for the growth of Arabidopsis (Gibeaut et al., 1997; Arteca and Arteca, 2000; Schlesier et al., 2003; Tocquin et al., 2003; Norén et al., 2004; Smeets et al., 2008; Conn et al., 2013). Some of the systems have often been designed for a specific purpose and could not be suitable for various experimental purposes (Arteca and Arteca, 2000; Schlesier et al., 2003; Norén et al., 2004); some of the systems have to use rockwool or sponge, which could prevent the collection of root tissues near the root-shoot junction and risk the shoot apical meristem in a flooding stress (Gibeaut et al., 1997; Smeets et al., 2008); some of the systems require specialized materials like seed holder, raft float and container (Arteca and Arteca, 2000; Tocquin et al., 2003; Conn et al., 2013). In addition, algae growing is a common problem when rockwool, sponge or agar-based plugs are used.

In 2013, Conn et al. developed an Arabidopsis hydroponic system by germinating seeds on the pierced cap of 1.5 ml microcentrifuge tube in the germination solution, and then transferring the seedlings to the modified 50 ml Falcon tubes which are placed in an aerated large container filled with the basal growth solution. This system has some advantages of preventing algae growth and ensuring the harvest of the whole root system. However, it is relatively complex to prepare some materials, such as the pierced lids of 50 ml Falcon tubes and two different nutrient solutions (the germination solution and the basal growth solution). Here, we simplified Conn’s method by using the materials and equipment that can be easily found in the laboratory or cheaply bought online, like the 0.5 ml microcentrifuge tube, recycled 1 ml pipette tip box, plastic bucket, and the air pump. Particularly, we only use ½ Hoagland nutrient solution during the whole life cycle of the plant to simplify the making of nutrient solutions. The construction of the hydroponic culture system we described here should be much simpler and cheaper compared with the previous systems (Tocquin et al., 2003; Conn et al., 2013). Our system also has the advantages of preventing algae growth, ensuring the harvest of the whole root system and maintaining high uniformity of the plants. In our hydroponic system, the plant can healthily complete the whole life cycle and can be treated and sampled at different growth stages according to research goals. The root system can be harvested totally without any damage. The hydroponic system can be used for various treatments like nutrient deficiencies, hormonal and chemical treatments, for shoot and root growth observation and measurement, and for shoot and root sample collection that can be used for various analyses at physiological, biochemical, metabolic, cellular and molecular levels. The size of a container used for plant growth can be adjusted based on the experimental goal and budget. For example, big bucket can be switched to 1 ml pipette tip box in the hydroponic culture system to save the cost of nutrient solution and chemical treatments if a large amount of plant materials is not necessarily required.