Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695, USA.
Tree Physiol. 2011 Aug;31(8):831-42. doi: 10.1093/treephys/tpr073. Epub 2011 Aug 9.
Carbon allocation to soluble phenolics (total phenolics, proanthocyanidins (PA)) and total non-structural carbohydrates (TNC; starch and soluble sugars) in needles of widely planted, highly productive loblolly pine (Pinus taeda L.) genotypes could impact stand resistance to herbivory, and biogeochemical cycling in the southeastern USA. However, genetic and growth-related effects on loblolly pine needle chemistry are not well characterized. Therefore, we investigated genetic and growth-related effects on foliar concentrations of total phenolics, PA and TNC in two different field studies. The first study contained nine different genotypes representing a range of genetic homogeneity, growing in a 2-year-old plantation on the coastal plain of North Carolina (NC), USA. The second study contained eight clones with different growth potentials planted in a 9-year-old clonal trial replicated at two sites (Georgia (GA) and South Carolina (SC), USA). In the first study (NC), we found no genetic effects on total phenolics, PA and TNC, and there was no relationship between genotype size and foliar biochemistry. In the second study, there were no differences in height growth between sites, but the SC site showed greater diameter (diameter at breast height (DBH)) and volume, most likely due to greater tree mortality (lower stocking) which reduced competition for resources and increased growth of remaining trees. We found a significant site × clone effect for total phenolics with lower productivity clones showing 27-30% higher total phenolic concentrations at the GA site where DBH and volume were lower. In contrast to the predictions of growth-defense theory, clone volume was positively associated with total phenolic concentrations at the higher volume SC site, and PA concentrations at the lower volume GA site. Overall, we found no evidence of a trade-off between genotype size and defense, and genetic potential for improved growth may include increased allocation to some secondary metabolites. These results imply that deployment of more productive loblolly pine genotypes will not reduce stand resistance to herbivory, but increased production of total phenolics and PA associated with higher genotype growth potential could reduce litter decomposition rates and therefore, nutrient availability.
广泛种植的、高生产力的火炬松（Pinus taeda L.）基因型的针叶中可溶性酚类物质（总酚类、原花青素（PA））和总非结构性碳水化合物（TNC；淀粉和可溶性糖）的碳分配可能会影响林分对食草动物的抵抗力，并影响美国东南部的生物地球化学循环。然而，遗传和生长相关因素对火炬松针叶化学的影响尚未得到很好的描述。因此，我们在两项不同的田间研究中调查了遗传和生长相关因素对叶片总酚类、PA 和 TNC 浓度的影响。第一项研究包含 9 个不同的基因型，代表了遗传同质性的范围，在美国北卡罗来纳州沿海平原（NC）的 2 年生林分中生长。第二项研究包含 8 个具有不同生长潜力的无性系，种植在两个地点（美国佐治亚州（GA）和南卡罗来纳州（SC））的 9 年生无性系试验中。在第一项研究（NC）中，我们发现总酚类、PA 和 TNC 没有遗传效应，基因型大小与叶片生物化学之间没有关系。在第二项研究中，两个地点的树高生长没有差异，但 SC 地点的胸径（DBH）和体积较大，这很可能是由于树木死亡率较高（较低的林分密度），减少了资源竞争，从而增加了剩余树木的生长。我们发现总酚类物质存在显著的地点×无性系效应，在 DBH 和体积较低的 GA 地点，低生产力无性系的总酚浓度高出 27-30%。与生长防御理论的预测相反，在体积较高的 SC 地点，无性系体积与总酚浓度呈正相关，而在体积较低的 GA 地点，PA 浓度与无性系体积呈正相关。总的来说，我们没有发现基因型大小和防御之间存在权衡的证据，并且改善生长的遗传潜力可能包括对一些次生代谢物的更多分配。这些结果表明，部署生产力更高的火炬松基因型不会降低林分对食草动物的抵抗力，但与较高基因型生长潜力相关的总酚类和 PA 的增加可能会降低凋落物分解率，从而降低养分的可利用性。
