Foliar boron fertilization as factor affecting the essential oil content and yield of oil components from flower heads of Arnica montana L. and Arnica chamissonis Less. cultivated for industry

The impact of foliar boron fertilization on the yield of flower heads as well as the chemical composition, content, and yield of essential oils (EO) of Arnica montana L. and A. chamissonis Less. were studied. The chemical composition of EO in the flower heads was examined with use of GC/MS. Fifty five compounds constitued ca. 94% of the total EO content in each of the species. The EO analysis of A. montana from Poland showed their chemical dissimilarity to other arnica populations in Europe. The foliar boron fertilization determined the yield of flower heads as well as the content and chemical composition of oils. The yield of flower heads was in the range from 1044.3 kg ha−1 to 1222.4 kg ha−1 in A. montana and from 903.6 kg ha−1 to 1081.5 kg ha−1 in A. chamissonis; however, the content of EO was from 0.174% to 0.200% and from 0.158% to 0.188%, respectively. The highest EO content in the inflorescences of the two plants was noted at the B rate of 200 g ha−1. Similarly, this dose caused a ca. 35% and 43% increase in the EO yield in A. montana and A. chamissonis, respectively. Boron rates higher than 100 g ha−1 had no effect on the crop yield, and dose higher than 200 g ha−1 had no effect on the EO content and yield of A. montana and A. chamissonis flower heads. Alpha-pinene, caryophyllene E, caryophyllene oxide, caryophyllene alcohol, dodecanal, and germacrene D mainly influenced the differences in EO. The highest yield of caryophyllene E and caryophyllene oxide were achieved in A. montana in comparison to A. chamissonis. On the other hand, the highest yield of alpha-pinene, germacrene D, cumene, caryophyllene alcohol, and decanal were found in A. chamissonis. The foliar boron fertilization of A. montana caused an increase in the yield of caryophyllene oxide and dodecane at the B dose of 100 g ha−1, and an increased yield of caryophyllene E and germacrene D at the dose of 200 g ha−1. However, in the case of A. chamissonis, the highest yield of germacrene D, cumene, and caryophyllene alcohol was noted after application of 200 g ha−1 of B, whereas the highest yield of alpha-pinene was observed after application of 300 g ha−1. Boron is an important factor responsible for differences of the oil chemical composition in A. montana and A.chamissonis flower heads and intensification of production of the main EO ingredients.