  When mature Arabidopsis thaliana seeds are dormant, their germination is
prevented in apparently favourable conditions. This primary dormancy can be
released during seed dry storage through a process called after-ripening whose
duration can last several months. To reduce this delay, cold atmospheric
plasmas (CAP) can be used as sources of reactive oxygen species capable of
inducing heterogeneous chemical reactions. While CAP are known to stimulate the
germination of various seed species, the relationship between CAP treatments
and the amorphous solid state of dry seeds remains unexplored. Here, we
demonstrate that seed dormancy can be alleviated using a cold plasma of ambient
air and that this alleviation can be amplified for seeds with high
water-content (typically 30 %DW) or seeds heated at 60 {\deg}C during plasma
treatment. Differential scanning micro-calorimetry shows that these
characteristics control the glassy/rubbery state of the seed cytoplasm. This
technique indicates also that a glass transition to the rubbery state
strengthens the CAP effects to alleviate seed dormancy. We propose that lower
cytoplasmic viscosity can promote the oxidative signaling induced by CAP which,
in turn, improves the germination process.
