Data for "Leaf-level metabolic changes in response to drought affect daytime CO₂ emission and isoprenoid synthesis pathways"

Data used to generate figures for the publication "Leaf–level metabolic changes in response to drought affect daytime CO₂ emission and isoprenoid synthesis pathways" from the B2 WALD campaign entitled. This item also includes metadata, figures, and a readme.Abstract:<br>In the near future, climate change will cause enhanced frequency and/or severity of droughts in terrestrial ecosystems, including tropical forests. Drought responses by tropical trees may affect their carbon use, including production of volatile organic compounds (VOCs), with implications for carbon cycling and atmospheric chemistry that are complex to predict. It remains unclear how metabolic adjustments by mature tropical trees in response to drought will affect their carbon fluxes associated with daytime CO₂ production and VOC emission. To address this gap, we used position–specific ¹³C–pyruvate labeling to investigate leaf CO₂ and VOC fluxes from four tropical species before and during a controlled drought in the enclosed rainforest of Biosphere 2. Overall, plants that were more sensitive to drought had greater reductions in daytime CO₂ production. Although daytime CO₂ production was always dominated by non–mitochondrial processes, the relative contribution of CO₂ from the tricarboxylic acid cycle tended to increase under drought. A notable exception was the legume tree Clitoria fairchildiana, which had less anabolic CO₂ production than the other species even under pre–drought conditions, perhaps due to more efficient refixation of CO₂ and anaplerotic use for amino acid synthesis. C. fairchildiana was also the only species to allocate detectable amounts of ¹³C label to VOCs, and was a major source of VOCs in the Biosphere 2 forest. In C. fairchildiana leaves, our data indicate that intermediates from the mevalonic acid pathway are used to produce the volatile monoterpene trans–beta–ocimene, but not isoprene. This apparent crosstalk between the mevalonic acid and methylerythritol phosphate pathways for monoterpene synthesis declined with drought. Finally, although trans–beta–ocimene emissions increased under drought, it was increasingly sourced from stored intermediates and not de novo synthesis. Unique metabolic responses of legumes may play a disproportionate role in the overall changes in daytime CO₂ and VOC fluxes in tropical forests experiencing drought.<br><br><i></i><i>For inquiries regarding the contents of this dataset, please contact the Corresponding Author listed in the README.txt file. Administrative inquiries (e.g., removal requests, trouble downloading, etc.) can be directed to [e-mail]</i>

本数据集用于生成B2 WALD项目中题为《叶片对干旱的代谢响应影响日间二氧化碳排放与类异戊二烯合成通路》的论文的配图，同时包含元数据、图表及说明文档。

摘要：
不久的将来，气候变化将使陆地生态系统（涵盖热带森林）面临的干旱事件频率升高、强度加剧。热带树木对干旱的响应可能会影响其碳利用过程，包括挥发性有机化合物（VOCs）的合成，这会给碳循环与大气化学带来难以精准预测的复杂影响。目前学界尚不清楚成熟热带树木针对干旱产生的代谢调控，会如何影响其与日间二氧化碳产生及挥发性有机化合物排放相关的碳通量。为填补这一研究空白，我们采用位置特异性¹³C标记丙酮酸（position-specific ¹³C-pyruvate）技术，在生物圈2号（Biosphere 2）的封闭雨林环境中，对四个热带树种分别在受控干旱处理前后的叶片二氧化碳与挥发性有机化合物通量进行了检测。总体而言，对干旱更为敏感的植物，其日间二氧化碳产生量的下降幅度更大。尽管日间二氧化碳产生始终以非线粒体途径为主，但三羧酸循环（tricarboxylic acid cycle）产生的二氧化碳占比在干旱条件下趋于上升。一个显著的例外是费尔柴尔德蝶豆（Clitoria fairchildiana）：即使在干旱前的正常条件下，其合成代谢相关的二氧化碳产生量也低于其他树种，这或许源于其更高效的二氧化碳再固定与用于氨基酸合成的回补途径利用。费尔柴尔德蝶豆（Clitoria fairchildiana）亦是唯一能将可检测量的¹³C标记物分配至挥发性有机化合物的树种，同时也是生物圈2号雨林中挥发性有机化合物的主要排放来源。在费尔柴尔德蝶豆的叶片中，我们的研究数据显示，甲羟戊酸途径（mevalonic acid pathway）的中间产物被用于合成挥发性单萜反式β-罗勒烯（trans-beta-ocimene），而非异戊二烯（isoprene）。这种用于单萜合成的甲羟戊酸途径与甲基赤藓醇磷酸途径（methylerythritol phosphate pathways）之间的串扰，会随干旱程度加剧而减弱。最后，尽管反式β-罗勒烯的排放会在干旱条件下升高，但其排放源越来越多地来自储存的中间产物，而非从头合成（de novo synthesis）。豆科树木独特的代谢响应，可能在遭受干旱的热带森林的日间二氧化碳与挥发性有机化合物通量的整体变化中，发挥远超其占比的重要作用。

若对本数据集的内容存在疑问，请联系README.txt文件中列出的通讯作者。行政类咨询（如删除请求、下载故障等）可发送至邮箱[e-mail]。