Allelopathic effects of epiphytic lichen Hypogymnia physodes (L.) Nyl. colonization on the spruce (Picea abies (L.) Karst.) bark

We examined the allelopathic response of young living spruce (Picea abies (L.) Karst.) bark to colonization by the lichen Hypogymnia physodes (L.) Nyl., expressed in enhanced accumulation of phenolic compounds. Total phenolics accumulation in lichen-occupied balk was 55% higher than in control, but only at sites where thalli were in direct contact with bark. Lichen colonization led to higher accumulation of non-tannin (40%) and tannin (75%) phenolic fractions. Content of extractable condensed tannins increased by 76% in bark with lichens (BWL) over the control. Condensed tannins in the solid residue remaining after the extraction were 4.9% dry weight (DW) in control and 5.6% DW in BWL. Total mass of extractable and non-extractable condensed tannins increased by 36% than control. The paper discusses the role of carbon pool derived from primary metabolites and directed to the phenylpropanoid pathway, responsible for synthesis of phenolic compounds. The share of carbon pool not used in the growth process due to inhibition by lichen metabolites and also not used in protein synthesis (decreased by 84% in BWL) may be directed to production of plant phenolics.