Exchanges of biogenic volatile organic compounds (BVOC) between plants and the atmosphere are likely to vary, in amount and composition, between different plant species but also for a single plant during its development. However, the effect of plant development stages, including senescence, on BVOC exchanges remains poorly investigated, especially in the case of crop plants. We investigated the BVOC exchange patterns for wheat plants, the most grown crop species worldwide, during seed maturation, senescence and after harvest. Fluxes were measured online, in situ, at the plant scale by combining automated chambers and a Proton Transfer - Reaction - Quadrupole ion guide - Time of Flight - Mass Spectrometer (PTR-Qi-Tof-MS). The high resolution and sensitivity of this method enabled the measurement of a large mass spectrum of compounds emitted at very small amounts, allowing a precise characterization of BVOC exchanges. We found that the overall BVOC emissions increased twofold during the senescence stage compared to the maturation stage. Methanol was found to be the most emitted compound (49–60% of the overall flux on a molar basis) followed by acetone (7.5–8.2% of the overall flux on a molar basis) during each developmental stage investigated. Acetaldehyde was another major emitted compound contributing mainly during late senescence to the overall flux (9.7%). When normalized for temperature and light conditions, most BVOC emissions increased during senescence, showing a clear effect of senescence on BVOC exchanges. Chamber emissions were comparable to whole ecosystem fluxes measured at the same site by eddy covariance the previous year. The OH reactivity of the emitted compounds was evaluated based on known reaction rate constants and was the largest during the first senescence stage, peaking at 12 s⁻¹ in the chambers. The results of this study show the need for considering plant phenology when computing BVOC emissions from crops.

植物与大气之间的生物挥发性有机化合物 (BVOC) 的交换在数量和组成上可能在不同植物物种之间以及在其发育过程中对于单个植物而言都不同。然而，植物发育阶段（包括衰老）对 BVOC 交换的影响仍然缺乏研究，特别是在作物植物的情况下。我们调查了小麦植物（全球种植最多的作物种类）在种子成熟、衰老和收获后的 BVOC 交换模式。在线测量通量，原位, 在工厂规模上通过结合自动化室和质子转移 - 反应 - 四极离子引导 - 飞行时间 - 质谱仪 (PTR-Qi-Tof-MS)。该方法的高分辨率和灵敏度使得能够测量以极少量排放的大量化合物的质谱，从而能够精确表征 BVOC 交换。我们发现，与成熟阶段相比，衰老阶段的整体 BVOC 排放量增加了两倍。在所研究的每个发育阶段，发现甲醇是排放最多的化合物（占总通量的 49-60%，以摩尔计），其次是丙酮（占总通量的 7.5-8.2%，以摩尔计）。乙醛是另一种主要排放化合物，主要在衰老晚期对总通量 (9.7%) 做出贡献。当对温度和光照条件进行归一化时，大多数 BVOC 排放在衰老过程中增加，表明衰老对 BVOC 交换的影响明显。室内排放量与前一年在同一地点通过涡度协方差测量的整个生态系统通量相当。根据已知的反应速率常数评估释放化合物的 OH 反应性，并且在第一个衰老阶段最大，在 12 s 达到峰值^-1在房间里。这项研究的结果表明，在计算作物的 BVOC 排放时需要考虑植物物候。