Hietz Peter, Rungwattana Kanin, Scheffknecht Susanne, George Jan-Peter
Department of Integrative Biology and Biodiversity Research, Institute of Botany, University of Natural Resources and Life Sciences, Vienna, Austria.
Department of Botany, Faculty of Science, Kasetsart University, Bangkok, Thailand.
Front Plant Sci. 2022 Apr 29;13:795941. doi: 10.3389/fpls.2022.795941. eCollection 2022.
Vessels are responsible for an efficient and safe water transport in angiosperm xylem. Whereas large vessels efficiently conduct the bulk of water, small vessels might be important under drought stress or after winter when large vessels are embolized. Wood anatomy can adjust to the environment by plastic adaptation, but is also modified by genetic selection, which can be driven by climate or other factors. To distinguish between plastic and genetic components on wood anatomy, we used a trial where trees from ten Central European provenances were planted in three locations in Austria along a rainfall gradient. Because wood anatomy also adjusts to tree size and in ring-porous species, the vessel size depends on the amount of latewood and thereby ring width, we included tree size and ring width in the analysis. We found that the trees' provenance had a significant effect on average vessel area (VA), theoretical specific hydraulic conductivity (Ks), and the vessel fraction (VF), but correlations with annual rainfall of provenances were at best weak. The trial site had a strong effect on growth (ring width, RW), which increased from the driest to the wettest site and wood density (WD), which increased from wet to dry sites. Significant site x provenance interactions were seen only for WD. Surprisingly, the drier site had higher VA, higher VF, and higher Ks. This, however, is mainly a result of greater RW and thus a greater proportion of latewood in the wetter forest. The average size of vessels > 70 μm diameter increased with rainfall. We argue that Ks, which is measured per cross-sectional area, is not an ideal parameter to compare the capacity of ring-porous trees to supply leaves with water. Small vessels (<70 μm) on average contributed only 1.4% to Ks, and we found no evidence that their number or size was adaptive to aridity. RW and tree size had strong effect on all vessel parameters, likely the greater proportion of latewood in wide rings. This should be accounted for when searching for wood anatomical adaptations to the environment.
导管负责被子植物木质部中高效且安全的水分运输。大型导管有效地传导大部分水分，而小型导管在干旱胁迫下或冬季大型导管发生栓塞后可能很重要。木材解剖结构可以通过塑性适应来适应环境，但也会受到遗传选择的影响，而遗传选择可能由气候或其他因素驱动。为了区分木材解剖结构中的塑性和遗传成分，我们进行了一项试验，将来自十个中欧种源的树木种植在奥地利沿降雨梯度的三个地点。由于木材解剖结构也会适应树木大小，并且在环孔材树种中，导管大小取决于晚材量，进而取决于年轮宽度，因此我们在分析中纳入了树木大小和年轮宽度。我们发现，树木的种源对平均导管面积（VA）、理论比水力传导率（Ks）和导管分数（VF）有显著影响，但与种源年降雨量的相关性充其量很弱。试验地点对生长（年轮宽度，RW）有强烈影响，RW从最干燥的地点到最湿润的地点增加，木材密度（WD）从湿润地点到干燥地点增加。仅在WD方面观察到显著的地点×种源相互作用。令人惊讶的是，较干燥的地点具有更高的VA、更高的VF和更高的Ks。然而，这主要是由于RW更大，因此在较湿润森林中晚材比例更大的结果。直径>70μm的导管平均大小随降雨量增加。我们认为，按横截面积测量的Ks不是比较环孔材树木为叶片供水能力的理想参数。平均而言，小型导管（<70μm）对Ks的贡献仅为1.4%，并且我们没有发现它们的数量或大小适应干旱的证据。RW和树木大小对所有导管参数有强烈影响，可能是因为宽年轮中晚材比例更大。在寻找木材解剖结构对环境的适应性时应考虑到这一点。
