Age, chemotype and overwintering practices control volatile emissions in Scots pine (Pinus sylvestris) seedlings

Small 5 to 7 cm seedlings appear to be less damaged by pine weevils (Hylobius abietis L.), one of the most economically devastating forest pests in Europe. In attempts to understand the underlying mechanisms, volatiles (VOC) released by the whole plant and wounded phloem of Scots pine (P. sylvestris L.) seedlings were investigated during the first year of growth. The changes in the VOC due to age/developmental stage and storage regimes were determined. Majority of the seedlings (84%) represented a '3-carene chemotype' and 15% an 'alpha-pinene chemotype'. 3.5 Week-old intact or wounded seedlings emitted mainly geranyl acetone and green leaf volatiles. Proportional increase of (+)-3-carene occurred during the growth and aging of intact '3-carene seedlings', while (+/-)-alpha-pinene changed in their phloem emissions. From 9.5 week onwards, the intact seedlings began to emit 2-phenylethanol. During winter dormancy, the pine odor enriched with estragole, 3-phenylpropanol and 4-ethyl-2-methoxyphenol. The latter one, together with 4-ethylphenol, was characteristic to the over-wintered in an outdoor area (OA). These results support the hypothesis that seedling attractiveness to herbivores depend on the plant age and overwintering practices. Considering the antimicrobial properties of volatiles, overwintering of plants under natural conditions may also ensure higher disease resistance of plants.