Is Natural Defense Capacity Correlated with Allocation of Dry Mass to the Stem in Loblolly Pine?

In addition to selecting loblolly pine (Pinus taeda L.) genotypes for superior growth, the concept of customized genetic selection may apply where tree vigor is threatened by insects and disease. A study conducted with seedlings from 15 loblolly pine genotypes found significant correlation between phenolic production and foliage mass when dry mass allocation to the stem was relatively low. Validation of this relationship in trees was attempted among four genetic sources of juvenile loblolly pine. Tree biomass allocation information was collected from six individuals per genotype at age 5 years in 2009. Five years later in January 2015, foliage and branch tip tissues were assessed for total phenolic concentrations. While tree biomass allocation differed significantly, total phenolic concentrations were similar among the four loblolly pine genotypes. Observations during this study suggest that our effort to validate this relationship in trees should be repeated during the growing season when carbon demands are at their highest and in stand conditions that exclude the possibility of light limitations to carbon fixation.