## 4 Discussion
Irrespective of the different dynamics of changes in the morphometric parameters observed in the two cultivars, the yield of seeds collected from treated seedlings was significantly higher in both cultivars, compared to the control. Both CP and EMF increased seed yield (seed number up to 46%, seed weight up to 70%) per plant of 'VB Vokiai' cultivar, but only CP had a positive effect on seed yield (seed number up to 85%, seed weight up to 97%) in 'VB Nojai'. Biomass production in both cultivars was strongly increased by CP5, CP7 and by EMF15 treatment. It is important to note that strong positive effects on biomass production were obtained in groups with the reduced emergence of buckwheat seedlings under field conditions (Table 2). The biochemical composition of the harvested buckwheat seeds was altered by seed treatments, and changes induced in antioxidant capacity, content of minerals, and secondary metabolites were cultivar-dependent. Treatment of buckwheat seeds with CP and EMF had a negative effect on the total amount of phenolic compounds in seed extracts, but changes induced in seed radical scavenging activity were stronger in 'VB Vokiai' seeds compared to 'VB Nojai'; moreover, the total phenolic compound content was reduced by CP treatment in 'VB Vokiai' seeds, and by EMF treatments in 'VB Nojai'. The effects on seed mineral content were cultivar-dependent also. The strongest effects were found on seed Fe and Zn content: CP7 reduced Fe content, and EMF increased Zn in 'VB Nojai' seeds, while CP7, EMF10 and EMF15 significantly increased Fe and decreased Zn content in 'VB Vokiai' seeds. Although the change in the amount of secondary metabolites per unit seed mass was significant only in the case of quercetin, considering the differences in seed yield between experimental groups, it was estimated that seed treatment had a strong effect (from 1.6 to 2.3 times) on secondary metabolite production per buckwheat plant. In this respect, EMF15 treatment was the most effective for 'VB Vokiai', whereas CP5 treatment-for 'VB Nojai'. The reasons behind the strong observed differences in the response to various modes of seed treatment (the effects on different plant traits) between the two cultivars of the same plant species remain to be understood. Certain genetically determined characteristics of molecular stress signal perception and transduction in seeds, or peculiarities in plant stress response pathways may be responsible for such differences. Seed treatments may induce cultivar-dependent shift in the balance of phytohormonal networks in plant tissues (in particular, stress response phytohormones such as abscisic, salicylic acids, or jasmonate [48]) leading to variety of induced changes at metabolic and physiological level. The significant increase in plant productivity may be also achieved by using biostimulants, and the observed effects variate in the range between 30% and 75% in dependence on the applied biostimulant type and plant species [49]; in addition, biostimulants can increase the nutritional quality of fruits and vegetables [50]. The effects of various types of biostimulants on the production of common buckwheat have been reported recently [51; 52; 53; 54]. It has been reported that seed soaking for 30 min. in solutions with biostimulants and microorganisms can boost nutrient content [51] and antioxidant activity [52] in buckwheat sprouts. Some plant growth biostimulants applied in the beginning of blooming reduced (by 4-12-fold) embryo abortion and thus contributed to higher seed yield in populations of common buckwheat with a biased flower morph ratio [53]. Silicon biostimulant applied 3 weeks after germination improved numerous morphometric parameters including increased seed number per plant (8%) and seed weight per plant (3 times). However, it is not easy to compare the effects of biostimulants on the productivity of common buckwheat with effects of seed treatments performed in this study due to the essential differences in the protocols used.