Respiration by plant roots can seasonally account for the majority of soil CO₂ production. At the plant scale level, the spatial distribution of soil CO₂ concentration is linked to root metabolic activity, which may vary with root physiological function and development stage of the root system, but also to soil moisture, a key variable affecting gas transport in soils. We performed rhizotron experiments with white lupine (Lupinus albus) to measure spatiotemporal dynamics of pCO₂ (CO₂ partial pressure) in the root zone and its dependence on root type and soil moisture. Via planar optode imaging, we measured pCO₂ daily at constant soil moisture (0.3 cm³ cm⁻³), and hourly in a consecutive drying-rewetting experiment, where soil moisture was increased from 0.1 to 0.3 cm³ cm⁻³. During the first 16 days of plant growth, regions of high CO₂ concentration formed around cluster roots, where pCO₂ locally increased to >20 %, while pCO₂ remained lower around lateral roots. Rewetting of dry soil had a pronounced effect on pCO₂: One hour after rewetting, pCO₂ at the root surface had increased significantly. Around cluster roots, the CO₂ accumulation zone strongly increased from 0.3 mm (dry soil) to 10 mm (wet soil), but remained narrower around lateral roots (1.5–1.8 mm in dry vs. wet soil). Our study demonstrates the applicability of planar optodes to monitor pCO₂ in the rhizosphere at different soil moisture levels, and highlights that local CO₂ concentration in the root zone is a function of root type and soil moisture.

_{植物根系的呼吸作用可季节性地占土壤CO 2}产生的大部分。在植物尺度水平上，土壤CO ₂浓度的空间分布与根系代谢活动有关，根系代谢活动可能随根系生理功能和根系发育阶段的不同而变化，而且还与土壤湿度有关，土壤湿度是影响土壤中气体输送的关键变量。我们用白羽扇豆（Lupinus albus ）进行了根管实验，以测量根区pCO ₂（CO ₂分压）的时空动态及其对根系类型和土壤湿度的依赖性。通过平面光极成像，我们在恒定的土壤湿度（0.3 cm³ cm ^{-3 ）下每天测量pCO} ₂，​​并在连续的干燥-再润湿实验中每小时测量一次，其中土壤湿度从0.1增加到0.3 cm³ cm ^- ³。在植物生长的前16天，簇根周围形成高CO _{2浓度区域，其中pCO 2}局部增加至>20%，而侧根周围pCO _{2仍然较低。干燥土壤的再润湿对pCO 2}具有显着影响：再润湿一小时后，根部表面的pCO ₂显着增加。在簇根周围，CO ₂积累区从 0.3 毫米（干土）大幅增加到 10 毫米（湿土），但在侧根周围仍然较窄（干土与湿土中为 1.5-1.8 毫米）。我们的研究证明了平面光极在不同土壤湿度水平下监测根际pCO ₂的适用性，并强调根区局部CO _{2浓度是根类型和土壤湿度的函数。}