Synergism of lyoniside and triterpenic acids in allelopathic potential of Vaccinium myrtillus L

V. myrtillus has a capacity to strongly restrict the neighbouring plants not only due to growth competition but also to allelopathic potential. This feature is important for boreal forest management. Due to the growing resistance to synthetic herbicides, natural allelochemicals are of interest for modern agriculture. The aim of this work was the study of the influence of lignan glycoside, lyoniside and two isomeric triterpenoids, oleanolic and ursolic acids, occurring in V. myrtillus rhizomes and detected in soil samples, on seed germination and seedling growth of Pinus sylvestris.

Plant material and soil samples were collected from the natural habitat in White Forest, central Poland and extracted in Soxhlet apparatus with ethyl ether and afterwards 30% ethanol. Triterpene acids were isolated from ether extracts by CC and TLC on silica gel, lyoniside was obtained from ethanol extracts by means of DCCC. In allelopathic bioassays on Ø100mm Petri dishes, tested compounds were supplied to 30 seeds of P. sylvestris either separately or mixed at the concentration of 10µg/ml, comparable to that in the soil. Triterpenic acids and lyoniside exerted slightly inhibitory effect on germination (reduction by 27 and 10%, respectively) and growth of seedlings (radicles by approx. 20%, shoots by 50 and 25%). However, the most dramatic effect was exerted by their mixture, which inhibited the germination by 80% and suppressed the growth by approx. 70%. These results point to the synergism of the activity of more polar lyoniside with less polar triterpene acids in V. myrtillus allelopathic potential.