Department of Viticulture & Enology, University of California, Davis, CA, USA.
School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA.
Tree Physiol. 2018 Aug 1;38(8):1180-1192. doi: 10.1093/treephys/tpy049.
A germplasm collection containing varied Juglans genotypes holds potential to improve drought resistance of plant materials for commercial production. We used X-ray computed microtomography to evaluate stem xylem embolism susceptibility/repair in relation to vessel anatomical features (size, arrangement, connectivity and pit characteristics) in 2-year-old saplings of three Juglans species. In vivo analysis revealed interspecific variations in embolism susceptibility among Juglans microcarpa, J. hindsii (both native to arid habitats) and J. ailantifolia (native to mesic habitats). Stem xylem of J. microcarpa was more resistant to drought-induced embolism as compared with J. hindsii and J. ailantifolia (differences in embolism susceptibility among older and current year xylem were not detected in any species). Variations in most vessel anatomical traits were negligible among the three species; however, we detected substantial interspecific differences in intervessel pit characteristics. As compared with J. hindsii and J. ailantifolia, low embolism susceptibility in J. microcarpa was associated with smaller pit size in larger diameter vessels, a smaller area of the shared vessel wall occupied by pits, lower pit frequency and no changes in pit characteristics as vessel diameters increased. Changes in amount of embolized vessels following 40 days of re-watering were minor in intact saplings of all three species highlighting that an embolism repair mechanism did not contribute to drought recovery. In conclusion, our data indicate that interspecific variations in drought-induced embolism susceptibility are associated with species-specific pit characteristics, and these traits may provide a future target for breeding efforts aimed at selecting walnut germplasm with improved drought resistance.
一个包含不同核桃基因型的种质资源收集可能有助于提高商业生产中植物材料的抗旱性。我们使用 X 射线计算机微断层扫描技术，评估了 3 种核桃属植物 2 年生幼树的木质部栓塞敏感性/修复与导管解剖特征（大小、排列、连通性和纹孔特征）之间的关系。体内分析表明，在干旱生境中生长的核桃麻核桃和 J. hindsii（均为原生种）以及在湿润生境中生长的 J. ailantifolia 之间存在种间栓塞敏感性差异。与 J. hindsii 和 J. ailantifolia 相比，J. microcarpa 的木质部对干旱诱导的栓塞更具抗性（在任何物种中都未检测到较老和当前年木质部栓塞敏感性差异）。在这三个物种中，大多数导管解剖特征的变化可以忽略不计；然而，我们检测到种间纹孔特征存在显著差异。与 J. hindsii 和 J. ailantifolia 相比，J. microcarpa 的低栓塞敏感性与较大直径导管中较小的纹孔大小、纹孔占据共享细胞壁的面积较小、纹孔频率较低以及随着导管直径增加纹孔特征没有变化有关。在重新浇水 40 天后，所有三个物种完整幼树中栓塞导管数量的变化很小，这表明栓塞修复机制并未促进干旱恢复。总之，我们的数据表明，干旱诱导栓塞敏感性的种间差异与种特异性纹孔特征有关，这些特征可能为选择抗旱性增强的核桃种质提供未来的目标。
