Rapid changes in induced non-volatile secondary metabolites in damaged Pinus massoniana Lamb

Plants initiate the development of defense mechanisms as soon as pests start to cause damage to them. In order to have a thorough understanding of the physiological mechanisms of the Pinus massoniana self-defense mechanism, and to provide a theoretical foundation for an effective ecological management of this plant, levels of tannin, polyamine and phenolic acids were analyzed in undamaged (UDL), insect-damaged (IDL) and artificially-damaged (ADL) leaves at different times. Results show that, although the content of tannin significantly increased in IDL and ADL compared to UDL, its peaks appeared earlier in ADL than in IDL treatment. Tannin concentration substantially increased again 48 h after IDL treatment. On the other hand, the damage mode considerably affected putrescine and spermidine levels in leaves. Their concentrations in IDL plants remained higher than in UDL after a relatively long time (72 h), but spermine was barely detected in any of the samples. In general, total content of phenol acids significantly increased in damaged leaf treatments (ADL and IDL), with a higher level in IDL for most of the investigated phenolic acids, except for ferulic acid. Our study showed that, when damaged by insects, Pinus massoniana rapidly produces substances required in resistance induction to insects in order to insure its self-protection.