Response of endogenous hormone in germination of millet seeds to optimal high voltage electrostatic field

For the past few years, the HVEF(high-voltage electric field) technology is gradually applied in agriculture, such as seed-selecting, disease-preventing, growth-promoting, and food preservation, etc. Pretreating seeds by HVEF has characteristics of simplicity, high efficiency, short processing time, low power and no pollution, etc, so it has become a hot research subject in agriculture field. Researches indicate that suitable treatment of HVEF is beneficial to the synthesis of adenosine triphosphate(ATP) and the activation of enzymes in seeds, improves the permeability of membrane, and strengthens the ability of resisting adversity and germination activity of the seeds. So far, since the mechanisms of applying HVEF technical involves both biology and physics field, the study of it has no definite conclusion, which restricts its generalization in agriculture to some extent. Millet has great potentialities as the staple food in the northern China due to its extensive adaptability and great nutrient content. As a signal of micromolecule, endogenous hormones induced by plant cell when accepting the specific environment signals, it can regulate plant physical responses even at the least concentration. So they are used to regulate seed germination directly or interactively. To reveal the control effects of dynamic content changes of endogenous hormone on germination activity of millet seeds treated by HVEF, Nongda 8(millet cultivar) was used as the testing subject, and an integrated method of combining quadratic general rotary unitized design and principal component analysis was also used to build model for optimal conditions. Under the optimized condition for HVEF, the dynamic content changes of endogenous hormone in the process of millet seeds germination were investigated in this paper. The results showed that pretreating seeds by HVEF can significantly influence germination vigor(P<0.05). The test for the fit of model was significant(P<0.01) and lack of fitting test was no significant(P>0.05). The regression determination coefficient R² reached to 0.9792(P<0.05). It indicated the goodness of simulation was better. The optimization scheme was that electric field strength was 340 kV/m and treatment time was 14 min. The coupling effects of two factors(electric field strength and treatment time) on germination composite index of Nongda 8 indicated there existed threshold in the treating millet by HVEF, and the effects of electric field strength were more than that of treatment time. Dynamic changes of endogenous hormone content in millet germination indicated that the optimal condition of treating millet by HVEF could induce the increase of IAA, ZR and GA content increased but inhibit the increase of ABA. When seed germinating IAA and GA increase quickly while ABA decreases quickly, and ZR was up to the maximum, which was beneficial for radicle to break through the seed coat, and to improve seed germinating. The dynamic content changes of endogenous hormones showed that GA/ABA, IAA/ABA ratio of millet seeds treated by HVEF were higher than control groups(untreated by HVEF), which indicated that the ratio change of millet endogenous hormones seeds treated by HVEF was incentives to improve germination activity of millet seeds. When radical length equals to twofold of seeds length, the radio of GA/ABA, IAA/ABA continued to increase, which indicated seedling grow had a close relation with its regulation and control. The results provide useful information for the application of HVEF technology in processing seeds in the agricultural production.