Thus, in the 5% treatment, the decrease in SSC appeared to be reduced as a result of the inhibition of respiration. Indeed, several studies on fresh produce have demonstrated that a hypoxic atmosphere inhibited respiration (Morales-Castro et al., 1994; Hertog et al., 2003; Wang and Long, 2014). Thus, in the current study, the observed delay in initial sprouting in the 5% treatment might have been caused by a hypoxic effect that inhibited the metabolism of respiratory substrates such as sugars and/or organic acids. In the 5% treatment,the O2 concentration during the gaseous phase of the potted soil was 12.4–14.4%. On the other hand, the O2 concentration during the same phase for the 10% treatment was 16.4–17.5%. Considering that sprouting under the 10% treatment was normal, for the roots, it appears that the threshold for delayed sprouting is an O2 concentration of ∼15%.