Purified hydrogen gas (99.99 %, v/v) generated from a
hydrogen gas generator (SHC-300; Saikesaisi
Hydrogen Energy Co., Ltd., Shandong, China) was
bubbled into 1,000 ml distilled water (pH 5.87, 25 °C)
at a rate of 150 mlmin−1 for 30 min, a sufficient duration
to saturate the solution with H2 (Bernardi et al. 2008).
Then, the corresponding HRW (pH 6.32, 25 °C) was
immediately diluted to the required concentrations [1, 5,
25, and 50 % concentration (v/v)]. In our experimental
conditions, the H2 concentration in freshly prepared
48 Plant Soil (2013) 370:47–57
HRW analyzed by GC was 0.22 mM and maintained at a
relative constant level in 25 °C for at least 12 h.