Department of Forest Sciences, Institute for Atmospheric and Earth System Research (INAR), Faculty of Agriculture and Forestry, University of Helsinki, Latokartanonkaari 7, PO Box 27, FI-00014 Helsinki, Finland.
Institute for Atmospheric and Earth System Research (INAR), Faculty of Sciences, University of Helsinki, Gustaf Hällströmin katu 2, PO Box 64, FI-00014 Helsinki, Finland.
Tree Physiol. 2024 Apr 3;44(4). doi: 10.1093/treephys/tpae029.
Drought is a major environmental stressor that limits seedling growth. Several studies have found that some ectomycorrhizal fungi may increase the drought tolerance of nursery-raised seedlings. However, the precise role that different ectomycorrhizal fungi species play in drought tolerance remains unclear. We evaluated the transpiration rate of Pinus sylvestris seedlings under drought stress in greenhouse conditions by exposing seedlings to 10 ectomycorrhizal fungi species, with different functional traits (exploration type and hydrophobicity), and to 3 natural soil inoculums. We measured the transpiration and water potential of the seedlings during a 10-day drought period and a 14-day recovery period. We then analyzed their root morphology, stem, needle, root biomass and needle chlorophyll fluorescence. We showed that exposing seedlings to ectomycorrhizal fungi or soil inoculum had a positive effect on their transpiration rate during the driest period and through the recovery phase, leading to 2- to 3-fold higher transpiration rates compared with the nonexposed control seedlings. Seedlings exposed to medium-distance ectomycorrhizal fungi performed better than other exploration types under drought conditions, but ectomycorrhizal fungi hydrophobicity did not seem to affect the seedlings response to drought. No significant differences were observed in biomass accumulation and root morphology between the seedlings exposed to different ectomycorrhizal fungi species and the control. Our results highlight the positive and species-specific effect of ectomycorrhizal fungi exposure on drought tolerance in nursery-raised Scots pine seedlings. The studied ectomycorrhizal fungi functional traits may not be sufficient to predict the seedling response to drought stress, thus physiological studies across multiple species are needed to draw the correct conclusion. Our findings have potential practical implications for enhancing seedling drought tolerance in nursery plant production.
干旱是限制幼苗生长的主要环境胁迫因素。有几项研究发现，一些外生菌根真菌可以提高苗圃培育幼苗的耐旱性。然而，不同外生菌根真菌物种在耐旱性中的确切作用尚不清楚。我们通过暴露幼苗于 10 种具有不同功能特征（探索类型和疏水性）的外生菌根真菌和 3 种自然土壤接种体，在温室条件下评估了干旱胁迫下欧洲赤松幼苗的蒸腾速率。我们在 10 天干旱期和 14 天恢复期测量了幼苗的蒸腾和水势。然后，我们分析了它们的根形态、茎、针叶、根生物量和针叶叶绿素荧光。我们表明，暴露于外生菌根真菌或土壤接种体的幼苗在最干旱时期和恢复阶段的蒸腾速率有积极影响，与未暴露对照幼苗相比，蒸腾速率提高了 2 到 3 倍。在干旱条件下，中距离外生菌根真菌暴露的幼苗比其他探索类型的表现更好，但外生菌根真菌的疏水性似乎并不影响幼苗对干旱的反应。暴露于不同外生菌根真菌物种的幼苗与对照之间在生物量积累和根系形态方面没有观察到显著差异。我们的研究结果突出了外生菌根真菌暴露对苗圃培育欧洲赤松幼苗耐旱性的积极和特异性影响。研究的外生菌根真菌功能特征可能不足以预测幼苗对干旱胁迫的反应，因此需要进行跨多个物种的生理研究以得出正确的结论。我们的研究结果对提高苗圃植物生产中幼苗的耐旱性具有潜在的实际意义。
