Birami Benjamin, Nägele Thomas, Gattmann Marielle, Preisler Yakir, Gast Andreas, Arneth Almut, Ruehr Nadine K
Institute of Meteorology and Climate Research - Atmospheric Environmental Research, Karlsruhe Institute of Technology KIT, Garmisch-Partenkirchen, 82467, Germany.
Department of Biology I, Plant Evolutionary Cell Biology, Ludwig-Maximilian University Munich, Planegg, 82152, Germany.
New Phytol. 2020 Jun;226(6):1607-1621. doi: 10.1111/nph.16471. Epub 2020 Mar 17.
Trees are increasingly exposed to hot droughts due to CO -induced climate change. However, the direct role of [CO ] in altering tree physiological responses to drought and heat stress remains ambiguous. Pinus halepensis (Aleppo pine) trees were grown from seed under ambient (421 ppm) or elevated (867 ppm) [CO ]. The 1.5-yr-old trees, either well watered or drought treated for 1 month, were transferred to separate gas-exchange chambers and the temperature gradually increased from 25°C to 40°C over a 10 d period. Continuous whole-tree shoot and root gas-exchange measurements were supplemented by primary metabolite analysis. Elevated [CO ] reduced tree water loss, reflected in lower stomatal conductance, resulting in a higher water-use efficiency throughout amplifying heat stress. Net carbon uptake declined strongly, driven by increases in respiration peaking earlier in the well-watered (31-32°C) than drought (33-34°C) treatments unaffected by growth [CO ]. Further, drought altered the primary metabolome, whereas the metabolic response to [CO ] was subtle and mainly reflected in enhanced root protein stability. The impact of elevated [CO ] on tree stress responses was modest and largely vanished with progressing heat and drought. We therefore conclude that increases in atmospheric [CO ] cannot counterbalance the impacts of hot drought extremes in Aleppo pine.
由于二氧化碳诱导的气候变化，树木越来越多地暴露于炎热干旱环境中。然而，二氧化碳在改变树木对干旱和热胁迫的生理反应方面的直接作用仍不明确。在环境二氧化碳浓度（421 ppm）或升高的二氧化碳浓度（867 ppm）条件下，用种子培育了阿勒颇松（Pinus halepensis）树。将1.5岁的树木，要么充分浇水，要么干旱处理1个月，转移到单独的气体交换室中，在10天的时间内温度从25°C逐渐升高到40°C。通过初级代谢物分析对整株树的地上部分和根系进行连续的气体交换测量进行补充。升高的二氧化碳浓度减少了树木的水分流失，表现为较低的气孔导度，从而在整个热胁迫过程中提高了水分利用效率。净碳吸收量大幅下降，这是由呼吸作用的增加驱动的，在充分浇水的处理（31 - 32°C）中呼吸峰值出现得比干旱处理（33 - 34°C）更早，且不受生长二氧化碳浓度的影响。此外，干旱改变了初级代谢组，而对二氧化碳浓度的代谢反应较为微妙，主要体现在根系蛋白质稳定性增强上。升高的二氧化碳浓度对树木胁迫反应的影响较小，并且随着热胁迫和干旱的加剧在很大程度上消失了。因此，我们得出结论，大气中二氧化碳浓度的增加无法抵消阿勒颇松遭受极端炎热干旱的影响。
