针对传统种子呼吸CO2浓度检测方法中检测精度低的问题, 为了满足测量需要, 提出一种采用可调谐二极管激光器吸收光谱技术的种子呼吸测量系统方案。该系统是由多次反射池结构的种子呼吸容器、分布反馈式激光器及其控制电路、光电转换及放大电路、数据采集电路、上位机软件等构成, 设计种子呼吸容器其空间体积为1.5 L, 激光器光源采用2 004 nm波段, 多次反射池光程为16 m。然后, 基于朗伯比尔定律, 通过波长调制吸收光谱技术, 利用二次谐波实时反演出种子呼吸过程中产生CO2气体的浓度。测试结果显示: 种子呼吸CO2浓度测量的稳定重复性为0.033%, CO2浓度的线性拟合度为0.999 38, CO2浓度检测极限为1.7 ppm。通过实验对糯玉米种子进行检测, 获得20 g玉米种子呼吸的变化曲线, 其12 h内变化量为2 750.5 ppm, 呼吸速率为229.2 ppm/h, 实验结果表明该系统能解决种子呼吸CO2浓度无法连续性测量、浓度检测精度低等问题。

To address the problem of low detection accuracy in the traditional method of seed-breathing CO2 concentration measurement, a seed-breathing measurement system based on tunable diode laser absorption spectroscopic technology was proposed to meet the needs of seed-breathing CO2 concentration measurements. First, the system was designed to consist of a seed-breathing container, a distributed feedback laser and control circuit, photoelectric conversion and an amplification circuit, a data acquisition circuit, and upper computer software. The space volume of the seed breathing container was 1.5 L, the laser source was in the 2 004-nm band, and the light path of the multiple reflection cell was 16 m. Then, based on Lamberts law and wavelength modulated absorption spectroscopy, the concentration of CO2 produced during seed respiration could be retrieved in real time using second harmonics. The stable repeatability of the CO2 concentration measurement in seed respiration is 0.033%, the linear fitting degree of CO2 concentration is 0.999 38, and the detection limit of CO2 concentration is 1.7×10-6. The change curve of 20-g maize seed respiration is obtained by testing waxy maize seeds. The amount of change in waxy maize seed respiration after 12 h is 2 750.5×10-6, and the respiration rate is 229.2×10-6/h. Experimental results show that the system can solve the inability for continuous measurement of CO2 concentration in seed respiration and the low precision of concentration detection.