Li Weibin, Zhang Hongxia, Pu Yingyi, Li Fan
State Key Laboratory of Herbage Improvement and Grassland Agro-Ecosystems; Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs; Engineering Research Center of Grassland Industry, Ministry of Education; College of Pastoral Agriculture Science and Technology, Lanzhou University, 768 Jiayuguan West Road, Lanzhou 730020, Gansu, China.
Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands/Shapotou Desert Research and Experiment Station, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, 320 Donggang West Road, Lanzhou 730000, Gansu, China.
Tree Physiol. 2025 Aug 5;45(8). doi: 10.1093/treephys/tpaf085.
Root exudates play a critical role in plant adaptation and the regulation of soil carbon and nutrient cycling, especially under climate change conditions. Despite their importance, the dynamics of root exudation under drought, particularly during drought-induced tree mortality, remain poorly understood. Here, we investigate how drought affects root exudation dynamics, root morphology traits and non-structural carbohydrate (NSC) concentrations in Qinghai spruce (Picea crassifolia Kom.) seedlings across the progression of drought-induced mortality. We conducted a two-stage drought manipulation experiment, beginning with moderate drought (50% irrigation reduction) followed by complete water cessation to induce lethal drought conditions. Our results reveal that drought significantly decreased the exudation rate of total organic carbon (C), while nitrogen (N) exudation rate remained unaffected, resulting in a lower C:N ratio in root exudates, indicative of a higher proportion of N-rich compounds. In addition, drought induced a shift in root morphological traits toward a more competitive strategy, marked by increased specific root length (SRL), specific root area (SRA) and branch intensity, and a reduction in root diameter (RD), root tissue density and root NSC concentrations. Notably, root exudation rates were negatively correlated with competitive root traits (higher SRL, SRA and branch intensity) and positively correlated with conservative traits (larger RD and root tissue density), suggesting that root exudation serves a more conservative function under drought conditions, prioritizing carbon storage and morphological adaptations over exudation. These findings provide valuable insights into the adaptive mechanisms of trees under drought stress, with implications for nutrient cycling, forest resilience and ecosystem productivity in water-limited environments.
根系分泌物在植物适应以及土壤碳和养分循环调节中发挥着关键作用，尤其是在气候变化条件下。尽管其重要性，但干旱条件下，特别是在干旱导致树木死亡期间，根系分泌的动态变化仍知之甚少。在此，我们研究了干旱如何影响青海云杉（Picea crassifolia Kom.）幼苗在干旱诱导死亡过程中的根系分泌动态、根系形态特征和非结构性碳水化合物（NSC）浓度。我们进行了一个两阶段的干旱处理实验，首先是中度干旱（减少50%的灌溉量），然后完全停止浇水以诱导致命的干旱条件。我们的结果表明，干旱显著降低了总有机碳（C）的分泌速率，而氮（N）分泌速率不受影响，导致根系分泌物中C:N比降低，表明富含N的化合物比例更高。此外，干旱导致根系形态特征向更具竞争力的策略转变，表现为比根长（SRL）、比根面积（SRA）和分支强度增加，以及根直径（RD）、根组织密度和根NSC浓度降低。值得注意的是，根系分泌速率与竞争性根系特征（较高的SRL、SRA和分支强度）呈负相关，与保守性特征（较大的RD和根组织密度）呈正相关，这表明在干旱条件下，根系分泌发挥着更保守的功能，优先考虑碳储存和形态适应而非分泌。这些发现为干旱胁迫下树木的适应机制提供了有价值的见解，对水分有限环境中的养分循环、森林恢复力和生态系统生产力具有重要意义。
