Accumulation of biomass and some macroelements in tomato plants grown in media with (+)-usnic acid

The results of studies on the effect of (+)-usnic acid synthesized by lichens on the growth, biomass accumulation and content of some macroelements in the organs of tomato plants are presented in this paper. The plants were grown hydroponically with (+)-usnic acid added to the media at various concentrations over a period of 21 days (from 10 days to 31 days after germination). At the highest subletal concentration of (+)-usnic acid (40 μM) under which the plants survived, the mean length of shoot, roots and leaf blade area attained about 13.6%, 11.5% and 0.5%, respectively, of the control values. In these conditions, the accumulation of dry matter was about 1.6%, 5.5% and 8.1% for leaves, stem and roots, respectively. The computed growth parameters (stem to roots, specific leaf weight and relative growth rate) were inversely proportional to the concentration of (+)-usnic acid in the medium, finally reaching a three to four times lower value than that determined in the control. Usnic acid reduced the content of the macroelements present in the plant tissues. In plants grown in media with an addition of 40 μM (+)-usnic acid, the macroelement content decreased by 25-35%, 48-55%, 65-69% and 60-70% for calcium, nitrogen, phosphorus and potassium, respectively, in comparison with the control.