Abstract. Rhizosheath size varies significantly with crop genotype, and root exudation is one among its driving factors. Unravelling the relationships between rhizosheath formation, root exudation and soil carbon dynamics may bring interesting perspectives in terms of crop breeding towards sustainable agriculture. Here we grew four pearl millet (C₄ plant type: δ¹³C of −12.8 ‰, F¹⁴C = 1.012) inbred lines showing contrasting rhizosheath sizes in a C₃ soil type (organic matter with δ¹³C of −22.3 ‰, F¹⁴C = 1.045). We sampled the root-adhering soil (RAS) and bulk soil after 28 days of growth under semi controlled condition. The Soil organic carbon (SOC) content, δ¹³C and F¹⁴C of soil samples were measured, and the plant-derived C amount and C_lost / C_new ratio in RAS were calculated. The results showed a significant increase in δ¹³C in the RAS of the four pearl millet lines compared to the control soil, suggesting that this approach was able to detect plant C input to the soil at early stage of pearl millet growth. The concentration of plant-derived C in RAS did not vary significantly between pearl millet lines, but the absolute amount of plant-derived C varied significantly when we considered the RAS mass of these different lines. Using a conceptual model and data from the two carbon isotopes measurements, we evidenced a priming effect for all pearl millet lines. Importantly, the priming effect amplitude was more important for the low-aggregation lines than for the high-aggregation ones indicating a better C sequestration potential of these latter.

中文翻译：

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通过碳同位素（δ13C和F14C）评估短生长期珍珠粟基因型的根沉积效率

摘要。根鞘大小因作物基因型而异，根系分泌物是其驱动因素之一。解开根鞘形成、根系分泌物和土壤碳动力学之间的关系可能会为作物育种向可持续农业带来有趣的视角。在这里，我们种植了四种珍珠粟（C ₄植物类型：δ ¹³ C 为 -12.8 ‰，F ¹⁴ C = 1.012）自交系在 C ₃土壤类型（δ ¹³ C 为 -22.3 ‰， F ¹⁴ C = 1.045)。在半控制条件下生长 28 天后，我们对附着根的土壤 (RAS) 和大块土壤进行了采样。土壤有机碳 (SOC) 含量，δ测定土壤样品的¹³ C和F ¹⁴ C，计算RAS中植物源C量和C_损失 /C_新比。结果表明δ ¹³显着增加与对照土壤相比，四个珍珠粟品系的 RAS 中的 C，表明这种方法能够检测珍珠粟生长早期土壤中植物 C 的输入。RAS 中植物源 C 的浓度在珍珠粟品系之间没有显着差异，但当我们考虑这些不同品系的 RAS 质量时，植物源 C 的绝对量变化很大。使用概念模型和来自两种碳同位素测量的数据，我们证明了所有珍珠粟品系的启动效应。重要的是，低聚集线的启动效应幅度比高聚集线更重要，表明后者具有更好的 C 封存潜力。