Optimal defense in pine trees: constitutive and induced allocation of resinand polyphenolics in Pinus radiata

Abstract: Optimal defense theory is based on the assumption that the within-plant allocation ofdefensive secondary metabolites is driven by the relative contribution to the overall fitness ofparticular plant tissues and their value in terms of costs. In this study, we examined theconstitutive and methyl jasmonate-induced strategy of optimal allocation of the two major pinedefenses, resin and polyphenolics, to two tissues with contrasting fitness value, stem and needles,along three parts of the plants (basal, medium and upper apical part) in Pinus radiata Don.seedlings. Induced responses of pine trees to methyl jasmonate were based on increasedconcentrations of total phenolics in leaves and resin compounds in the stem, but not significantchanges were observed for phenolics in phloem either resin in needles. We observed a markedgradient of allocation within the plant, with different patterns between basal, medium and apicaltissues of the pines. Resin content in the stem tissues was greater along an upward gradient.However, in leave tissues, both resin and phenolics content became greater along a downwardsgradient. Our results indicate a marked pattern of allocation of defenses along the plant andamong tissues relevant for plant fitness, which constitute the first confirmation of the OptimalDefense Theory for pine trees.