The Study On Dispersive Infrared CO₂ Analyzer In Measuring Photosynthetic Rate Of Plant Population

In order to better understand plant photosynthetic rate,in this study,the new plant photosynthetic measurement system was coupled of measurements of non-dispersive infrared?NDIR?technology to analyze CO₂,the new system was integrated with air temperature and humidity sensors,soil temperature sensors,soil moisture sensors,photosynthetically active radiation sensors,data collector,and other accessories.Through the laboratory performance test and field test,the test system was debugged and optimized.Compared the new system with the systems of the exhaust infrated CO₂ analyzer LI-840A?Li-cor,USA?and the dispersive infrared CO₂ analyzer GMP222?Vaisala,Finnish?,three major aspects were analyzed which werethe feasibility report,the normalization and the relative error in measuring plant plant photosynthetic rate.The results showed that:According to improving and texting the calibration method,filter and other aspects of the suction CO₂ infrared gas analyzer,the performance of the sensors was constantly increased.The zero measurement was 0.73±0.3ppm,under the full scale was 3000 ppm,the observed value was 3000±8ppm under the 380 ppm standard gas conditions,the observed value was 380±2ppm.Therefore,there was a good accuracy.the performance of the RR220 was stable,with long-term,continuous test of local experiment and the air measurements of different types,especially improving the control of noise in the system.During the single plant photosynthesis rate measured,the response time of RR220 was 30s lower than that of LI-840 A in the stating photosynthetic measurement time,in the end step,the sensors response time was recovered 90 s,which was 20 s slower than LI-840 A.The response time in the beginning respiratory measuring was 10 s,and the end time was 180 s.Taking LI-840 A as a standard,it is noted that the assimilation box time was 3min every time,and the first 30 s data was invalid,the interval of two measurements was about 3min.By using LI-840 A as a reference standard,the results consistency of suction CO₂ infrared gas analyzer was discussed.During the photosynthesis and respiration measurements,there was a good consistency between RR220 and LI-840 A,and the performance of RR220 was better than LI-840 A in the scientific measurement.With the increasing photosynthetic rate,the relative error between RR220 and LI-840 A was decreased.Under the low photosynthetic rate?0⁵?mol·m-2·s-1?,therelative error was usually-15%⁵0%.Comparatively,during the relatively low photosynthetic rate?5¹0 ?mol·m-2·s-1?,the relative error was-15%²5%;under the middle photosynthetic rate?10²0?mol·m-2·s-1?,the relative error was-15%¹0%;under the high photosynthetic rate?20³0?mol·m-2·s-1?,the relative error was-10%⁵%;under the higher photosynthetic rate?30?mol·m-2·s-1?,the relative error between RR220 and LI-840 was lowest?-5%¹%?.Compared with pumping infrared CO₂ analyzer,dispersive infrared CO₂ analyzer was applied in plant population photosynthetic measurement system,the gas path became simplified,the size of sensor was smaller and portable with lower power became simplified,the size of sensor was smaller and portable with lower power and cost of production,consequently,it is more suitable for long-term moblitity field observations of plant populations,whih explore a new method of measurement of photosynthesis.