Key Message

Hybrid saplings were more reactive to soil water deficit than Japanese and European larch. European larch had hydraulically safer wood and anisohydric behavior, Japanese and hybrid larch showed isohydric strategy.

Abstract

Deciduous larch species could be an alternative to evergreen conifers in reforestation, but little is known about drought sensitivity of their saplings. The effect of an experimental drought on hydraulics and quantitative wood anatomy was tested on saplings of European larch (EL, Larix decidua), Japanese larch (JL, Larix kaempferi) and their hybrid (HL). Across species, biomass, transpiration rate and relative water content were higher in controls than in drought stressed trees, but transpiration efficiency was lower. JL had the highest transpiration efficiency under drought, and EL the lowest, coinciding with slower growth of EL. Wood of EL formed before drought was hydraulically safer as shown by higher wall/lumen ratio and lower pit cavity area. EL neither had a significant increase in transpiration efficiency nor a reduction in transpiration rate under drought, suggesting that the stomata remained open under soil water deficit. HL saplings were the most reactive to water shortage, indicated by intra-annual density fluctuations and a decrease in relative water content of the sapwood. Significant reduction in transpiration by HL suggested a higher stomatal sensitivity, while the same leaf surface area was maintained and radial growth was still similar to its best parent, the JL. The latter showed a significantly lower leaf surface area under drought than controls. EL, with its hydraulically safer wood, followed an anisohydric behavior, while JL and HL revealed an isohydric strategy. Altogether, our results suggest species dependent acclimations to drought stress, whereby HL followed the strategy of JL rather than that of EL.

中文翻译：

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两种落叶松物种及其杂交种对干旱胁迫的生理和解剖学反应不同

关键信息

与日本和欧洲落叶松相比，杂交树苗对土壤水分亏缺的反应更大。欧洲落叶松具有水力更安全的木材和等水行为，日本和混合落叶松表现出等水策略。

抽象的

落叶落叶松树种可以替代常绿针叶树重新造林，但对其树苗的干旱敏感性知之甚少。在欧洲落叶松 (EL, Larix decidua )、日本落叶松 (JL, Larix kaempferi )的树苗上测试了实验性干旱对水力学和定量木材解剖学的影响) 及其混合 (HL)。在不同物种中，对照的生物量、蒸腾速率和相对含水量高于干旱胁迫的树木，但蒸腾效率较低。JL 在干旱条件下蒸腾效率最高，EL 最低，与 EL 增长较慢相吻合。干旱前形成的 EL 木材在水力上更安全，如较高的壁/流明比和较低的坑腔面积所示。EL 在干旱条件下既没有显着提高蒸腾效率，也没有降低蒸腾速率，这表明在土壤水分亏缺的情况下气孔保持开放。HL 树苗对缺水的反应最大，这表现为年内密度波动和边材相对含水量的下降。HL显着减少蒸腾作用表明气孔敏感性更高，而保持相同的叶表面积，径向生长仍与其最佳亲本 JL 相似。后者在干旱条件下的叶表面积显着低于对照。EL 具有液压更安全的木材，遵循非等水行为，而 JL 和 HL 则揭示了等水策略。总而言之，我们的结果表明物种依赖于干旱胁迫的适应，因此 HL 遵循 JL 的策略而不是 EL 的策略。