## 4 Discussion  
Herbs are a good source of phenolic acids in our diet. The obtained results show that organic herbs contained significantly more total phenolic acids than conventional herbs. This finding is similar to what was reported in some experiments which showed the mean value of total phenolic acids in fresh medicinal plants (organic) was 33.49 mg 100 g\({}^{-1}\) FW and (conventional) 32.52 mg 100 g\({}^{-1}\) FW, as well as in herbs (organic) 31.10 mg 100 g\({}^{-1}\) FW and (conventional) 26.50 mg 100 g\({}^{-1}\) FW [18; 19]. Unfortunately, many research results presented in the literature regarding the impact of organic and conventional cultivation on the content of phenolic acids in herbs do not explain the mechanisms of this phenomenon [18; 19]. Organic herbs are cultivated under strict rules when easily available fertilizers cannot be used. We can only suppose that higher level of phenolic acids in our organic herbs is an effect of different kinds of fertilization, especially potassium fertilization. In another presented experiment, organic potato was characterized by higher phenolic acids concentration and tthe authors explained this phenomenon by different fertilization regime [20]. In one experiment with organically and conventionally grown leafy vegetables, the higher amount of phenolic acids in organic plants was explained as a plant reaction for a biotic and abiotic stresses [10]. The species and variety of plant significantly influence phenolic acid accumulation in herbs. As we demonstrated in the experiment, two examined herbs (marjoram and bear's garlic) were characterized by the highest level of identified phenolic acids, while basil and oregano contained significantly lower individual phenolic acids. The diversification of the concentration of phenolic acids between species is an effect of genetic factors. Different polyphenol compounds such as phenolic acids play important roles in plant-microbe interactions/symbiosis. Phenolic acids act as signaling molecules in the initiation of plant-microbe symbioses [21]. In organic systems, plants are cultivated with organic fertilizers and the biological activity of the soil is greater than in conventional farming The higher level of phenolic acids in organic plants is an effect of \"chemical signaling\" between plant and soil microbes [22]. We found the higher level of total phenolic acids and gallic acid in organically-produced herbs in both years of the experiment. Gallic acid is a very important phenolic acid induced by Rhizobia in rice resistant to Rhizobia [23]. The higher concentration of ferulic acid could stimulate root growth inhibition and lead to slower plant growth and plant dry mass accumulation [24]. This observation is in accordance with the present results. It is worth noting that conventional herbs with a higher ferulic acid concentration also had a lower concentration of gallic acid. Flavonoids have antioxidant abilities and protect plants from various biotic and abiotic stresses. The role of secondary metabolic pathways in plant responses is to cope with oxidative stress, which is responsible for the synthesis of flavonoids [25]. Organic herbs and medicinal plants contain a higher level of flavonoids [18; 19]. The higher concentration of flavonoids in fresh organic herbs and medicinal plants is an effect of agricultural condition used in that system. Organic basil contained 7.03 mg g\({}^{-1}\) FW flavonoids in control combination, 8.23 mg g\({}^{-1}\) in 100% compost, and 11.48 mg g\({}^{-1}\) FW in compost with bioactivator [26]. The authors found a link between organic matter applying and the concentration of flavonoids in basil. They may be attributed to the C/N theory. In natural conditions, when nitrogen is readily available (conventional agriculture), plants would primarily make compounds with high nitrogen concentration, (proteins, amino acids for growth, and \(N\)-containing secondary metabolites such as alkaloids).