Department of Phytology, Technical University, Zvolen, Slovakia.
Ann Bot. 2013 Feb;111(2):215-27. doi: 10.1093/aob/mcs274. Epub 2012 Dec 21.
Previous studies have shown that Ophiostoma novo-ulmi, the causative agent of Dutch elm disease (DED), is able to colonize remote areas in infected plants of Ulmus such as the leaf midrib and secondary veins. The objective of this study was to compare the performances in leaf traits between two Dutch elm hybrids 'Groeneveld' and 'Dodoens' which possess a contrasting tolerance to DED. Trait linkages were also tested with leaf mass per area (LMA) and with the reduced Young's modulus of elasticity (MOE) as a result of structural, developmental or functional linkages.
Measurements and comparisons were made of leaf growth traits, primary xylem density components, gas exchange variables and chlorophyll a fluorescence yields between mature plants of 'Groeneveld' and 'Dodoens' grown under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to reveal nanomechanical properties of the cell walls of tracheary elements such as MOE, adhesion and dissipation.
'Dodoens' had significantly higher values for LMA, leaf tissue thickness variables, tracheary element lumen area (A), relative hydraulic conductivity (RC), gas exchange variables and chlorophyll a fluorescence yields. 'Groeneveld' had stiffer cell walls of tracheary elements, and higher values for water-use efficiency and leaf water potential. Leaves with a large carbon and nutrient investment in LMA tended to have a greater leaf thickness and a higher net photosynthetic rate, but LMA was independent of RC. Significant linkages were also found between the MOE and some vascular traits such as RC, A and the number of tracheary elements per unit area.
Strong dissimilarities in leaf trait performances were observed between the examined Dutch elm hybrids. Both hybrids were clearly separated from each other in the multivariate leaf trait space. Leaf growth, vascular and gas exchange traits in the infected plants of 'Dodoens' were unaffected by the DED fungus. 'Dodoens' proved to be a valuable elm germplasm for further breeding strategies.
先前的研究表明，荷兰榆树病（DED）的病原体，Ophiostoma novo-ulmi，能够在感染的榆树植物的远程区域定殖，如叶片中脉和二级脉。本研究的目的是比较两种荷兰榆树杂种‘Groeneveld’和‘Dodoens’的叶片性状表现，这两种杂种对 DED 的耐受性存在差异。还测试了性状之间的联系，包括叶面积比（LMA）与由于结构、发育或功能联系而导致的简化杨氏弹性模量（MOE）。
在田间条件下，对成熟的‘Groeneveld’和‘Dodoens’植株进行了叶片生长性状、初生木质部密度成分、气体交换变量和叶绿素 a 荧光产量的测量和比较。最近开发的原子力显微镜技术，即峰值力定量纳米力学映射，用于揭示木质部元素细胞壁的纳米力学特性，如 MOE、附着力和耗散。
‘Dodoens’的 LMA、叶片组织厚度变量、木质部元素腔面积（A）、相对水力传导率（RC）、气体交换变量和叶绿素 a 荧光产量的数值显著较高。‘Groeneveld’的木质部元素细胞壁较硬，水分利用效率和叶片水势较高。在 LMA 上投入大量碳和营养物质的叶片往往具有较大的叶片厚度和较高的净光合速率，但 LMA 与 RC 无关。MOE 与一些血管性状之间也存在显著联系，如 RC、A 和单位面积的木质部元素数量。
在所检查的荷兰榆树杂种之间观察到叶片性状表现的强烈差异。在多维叶片性状空间中，这两种杂种明显相互分离。‘Dodoens’感染植物的叶片生长、血管和气体交换性状不受 DED 真菌的影响。‘Dodoens’被证明是进一步育种策略的有价值的榆树种质资源。
