Loss of sciophilous character of crop seeds subjected to barrier discharge produced by repetitive polarity-reversed voltage pulses

摘要

This study presents the altered photosensitivity of several sciophilous seeds subjected to non-equilibrium plasma produced by polarity-reversed voltage pulses in ns range. It is well known that the photosensitivity of seeds can classified into two types, sciophilous (light-inhibited) and heliophilous (light-favoured). In this study, three kinds of sciophilous seeds, tomato, daikon radish and eggplant, are used as test samples. Dielectric barrier discharge are repeatedly propagated along the surface of the seeds on a glass barrier between plane-plane electrodes. After the discharge treatment, the seeds are incubated on a wet Alter paper with a dark-room condition for sciophilous plants or with an irradiating condition for heliophilous plants. The cultivation result of tomato seeds, regardless of the discharge treatment time (0, 5, 10, 20, 30 min), is that most of the seeds starts to grow roots within 4 days and then germinate within 1 week in dark-room condition. Both the leaf size and root length after 2 weeks of incubation do not depend on the discharge treatment in dark-room condition. On the other hand, the seeds without discharge treatment have a lower ability for germination in irradiating condition because of their sciophilous properties. However, the germination ratio of the seeds in irradiating condition increases with the increase of the discharge treatment time. This interesting phenomenon implies that the loss of sciophilous characteristics due to molecular structure change of photoreceptor in the seed coat is caused by the repetitive barrier discharges. Results for daikon radish shows the same tendency as tomato seeds. But, the germination of eggplant seeds were inhibited by the discharge treatment. On the other hand, germination ratio for eggplant seeds strongly decreased by the 30 min discharge treatment regardless of the irradiation conditions.