Due to temperature changes, forests are expected to encounter more stress than before, both in terms of biotic factors, such as increased insect attacks, and abiotic factors, such as more frequent droughts. Priming trees to respond to these changes faster and more effectively would be beneficial. Induced systemic resistance (ISR) is a mechanism that is turned on when plants encounter unfavorable conditions. Certain elicitors, such as jasmonic acid (JA) are known to induce plants' metabolic response. However, even though studies on ISR in herbaceous species are common and varied ISR elicitors can be used in agriculture, the same cannot be said about trees and forestry enterprises. We aimed to investigate whether JA used in different concentrations could induce metabolic changes (total phenol content, total flavonoid content, photosynthesis pigment content, antioxidant enzyme activity) in Pinus sylvestris seedlings and how this varies between different pine half-sib families (genotypes). After six weeks with a single application of JA, pine seedlings in several pine genetic families exhibited increased antioxidant enzyme activity, total phenol content and carotenoid content that correlated positively with JA concentrations used. Results from other genetic families were varied, but in many cases, there was a significant response to JA, with a noticeable increase as compared to the unaffected group. The impact on chlorophyll content and flavonoids was less noticeable overall. A positive effect on seedling growth parameters was not observed in any of the test cases. We conclude that JA can induce systemic resistance after a single application exogenously in P. sylvestris seedlings and recommend that the use of JA needs to be optimized by selecting appropriate concentrations.
Keywords: Scots pine; antioxidant enzymes; carotenoids; chlorophyll; flavonoids; phenols; secondary metabolism.