The purpose of this study was to investigate the drought response mechanisms that underlie carbon allocation and carbon demand in roots. The correlations between root traits and the amount of carbon (C) allocated to different orders of roots were tested using 13C pulse labeling. The amount of 13C was measured by quantifying the CO2 emitted from respiring roots of Pinus tabuliformis excised 0, 1, 3, 9, 21, 81 and 120 days after labeling. 1) Moderate drought stress significantly increased the root to shoot biomass ratio, the biomass ratio of the first three orders to the 4th- and 5th-order roots, and the cumulative root length and root area of the 1st-order roots. 2) 120 days after labeling, 13C amount allocated to 1st- and 2nd-order roots was significantly higher in all drought stress treatments than adequate water supply treatment, with the exception of 13C in 1st-order roots undergoing the severe drought stress treatment. Root respiration was significantly and positively correlated with 13C in the 1st- and 2nd-order roots in all drought stress treatments. 3) The 13C ratios of all the droughted treatments vs water supply treatment were significantly higher in the 1st- and 2nd-order roots than in the 4th- and 5th-order roots, with the exception of the 1st-order roots in the most severe drought treatment. Drought stress elevated C demand in lower-order roots by increasing the lower-order root respiration rate and by expanding the photosynthate allocation to the fine roots to enhance their structural growth.

中文翻译：

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干旱胁迫下油松幼苗根系短期碳分配与根系呼吸的异质性

本研究的目的是调查作为根系碳分配和碳需求基础的干旱响应机制。使用 13C 脉冲标记测试根性状与分配给不同根级的碳 (C) 量之间的相关性。13C 的含量是通过量化从标记后 0、1、3、9、21、81 和 120 天切下的油松呼吸根中排放的 CO2 来测量的。1) 中度干旱胁迫显着提高了根冠生物量比、前三阶与四阶和五阶根的生物量比，以及一阶根的累积根长和根面积。2）标记后120天，分配给一级和二级根的13C量在所有干旱胁迫处理中均显着高于充足供水处理，除了经历严重干旱胁迫处理的一级根中的 13C 外。在所有干旱胁迫处理中，根呼吸与一级和二级根中的 13C 显着正相关。3）所有干旱处理与供水处理的 13C 比在 1 级和 2 级根中均显着高于在 4 级和 5 级根中，除最严重的 1 级根外干旱处理。干旱胁迫通过增加低阶根的呼吸速率和通过扩大细根的光合产物分配以增强其结构生长来提高低阶根的碳需求。在所有干旱胁迫处理中，根呼吸与一级和二级根中的 13C 显着正相关。3）所有干旱处理与供水处理的 13C 比在 1 级和 2 级根中均显着高于在 4 级和 5 级根中，但在最严重的 1 级根中除外干旱处理。干旱胁迫通过增加低阶根的呼吸速率和通过扩大细根的光合产物分配以增强其结构生长来提高低阶根的碳需求。在所有干旱胁迫处理中，根呼吸与一级和二级根中的 13C 显着正相关。3）所有干旱处理与供水处理的 13C 比在 1 级和 2 级根中均显着高于在 4 级和 5 级根中，除最严重的 1 级根外干旱处理。干旱胁迫通过增加低阶根的呼吸速率和通过扩大细根的光合产物分配以增强其结构生长来提高低阶根的碳需求。除了最严重干旱处理中的一阶根。干旱胁迫通过增加低阶根的呼吸速率和通过扩大细根的光合产物分配以增强其结构生长来提高低阶根的碳需求。除了最严重干旱处理中的一阶根。干旱胁迫通过增加低阶根的呼吸速率和通过扩大细根的光合产物分配以增强其结构生长来提高低阶根的碳需求。