  Seeds have been packed in a dielectric barrier device where cold atmospheric
plasma has been generated to improve their germinative properties. A special
attention has been paid on understanding the resulting plasma electrical
properties through an equivalent electrical model whose experimental validity
has been demonstrated here. In this model, the interelectrode gap is subdivided
into 4 types of elementary domains, according to whether they contain electric
charges (or not) and according to their type of medium (gas, seed or
insulator). The model enables to study the influence of seeds on the plasma
electrical properties by measuring and deducing several parameters (charge per
filament, gas capacitance, plasma power, ...) either in no-bed configuration
(i.e. no seed in the reactor) or in packed-bed configuration (seeds in the
reactor). In that second case, we have investigated how seeds can influence the
plasma electrical parameters considering six specimens of seeds (beans,
radishes, corianders, lentils, sunflowers and corns). The influence of
molecular oxygen (0-100 sccm) mixed with a continuous flow rate of helium (2
slm) is also investigated, especially through filaments breakdown voltages,
charge per filament and plasma power. It is demonstrated that such bed-packing
drives to an increase in the gas capacitance, to a decrease in the
beta-parameter and to variations of the filaments' breakdown voltages in a
seed-dependent manner. Finally, we show how the equivalent electrical model can
be used to assess the total volume of the contact points, the capacitance of
the seeds in the packed-bed configuration and we demonstrate that germinative
effects can be induced by plasma on four of the six agronomical specimens.
