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 d of growth under a semi-controlled condition. The soil organic carbon (SOC) content and δ¹³C and F¹⁴C of soil samples were measured and the plant-derived C amount and C_lost $/$ C_new ratio in the 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 into the soil at an early stage of pearl millet growth. The concentration of plant-derived C in the 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 (C_lost $/$ C_new ratio) was higher for the small rhizosheath (low-aggregation) line than for the large rhizosheath (high-aggregation) ones, indicating a better C sequestration potential of the latter.

中文翻译：

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用碳同位素（δ13C和F14C）在短生长期评估珍珠粟基因型的根系沉积效率

根鞘大小随作物基因型而显着变化，根系分泌物是其驱动因素之一。揭示根鞘形成、根系渗出和土壤碳动态之间的关系可能会为可持续农业的作物育种带来有趣的视角。在这里，我们种植了四种珍珠粟（C ₄ 植物类型：δ ¹³ C of − 12.8 ‰，F ¹⁴ C  =  1.012）自交系，在 C ₃土壤类型中显示出不同的根鞘大小（有机质，δ ¹³ C of − 22.3 ‰， F ¹⁴ C  = 1.045)。我们在半控制条件下生长 28 d 后对根附着土壤 (RAS) 和大块土壤进行采样。测定土壤样品的土壤有机碳（SOC）含量和δ ¹³ C、F ^{14 C及植物源C量和C}_损失 $/$ 计算 RAS 中的C_新比率。结果显示，与对照土壤相比，4 个珍珠粟品系的 RAS 中δ ¹³ C 显着增加，表明该方法能够在珍珠粟生长的早期检测到植物 C 输入土壤。RAS 中植物来源 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，植物来源 C 的绝对量差异很大。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，启动效应幅度（C _loss $/$ 小根鞘（低聚集）系的C_新比率）高于大根鞘（高聚集）系，表明后者具有更好的 C 封存潜力。