【摘要】 为提高开顶气室（open-top chamber,OTC）模拟气候变化研究植物生理响应的控制效果,基于前期OTC控制系统基础,对气室结构、控制系统及监测系统改进升级。对改进后的OTC控制系统采集了试验期间5月—10月OTC气室内CO₂浓度、温度及空气相对湿度实时数据分析模拟效果,结果表明:改进后的OTC控制系统能够控制CO₂浓度达到试验预设浓度梯度,在试验期OTC气室内监测的CO₂浓度平均值对照组（CK）为369.33μmol·mol^-1,处理1组（TR1）为558.35μmol·mol^-1,处理2组（TR2）为772.71μmol·mol^-1;CO₂浓度波动范围TR1组为551.82—572.40μmol·mol^-1,变幅为20.58μmol·mol^-1;TR2组为756.71—779.79μmol·mol^-1,变幅为23.08μmol·mol^-1,满足试验预设模拟要求;气室内不同处理间温度、空气相对湿度差异均不显著（p>0.05）。改进后的OTC控制系统模拟效果好,可用于研究植物响应气候变化的模拟试验。更多还原

【Abstract】 Background,aim,and scope Enhancement of carbon dioxide（CO₂）in the atmosphere has received great attention due to its potential repercussion on global warming and direct effects on the vegetation,especially with a potential increase in atmospheric CO₂ level from 400μmol·mol^-1 to 1000μmol·mol^-1 by the end of21st century according with currents environmental studies.Therefore,development of new technologies on controlled environment conditions are needed to investigate plant response to CO₂ enhancements and its possible repercussion on world food security.Among the controlled environment facilities such as the free air CO₂ enrichment（FACE）,soil-plant-atmosphere research chambers（SPAR）,and CO₂-temperature gradient chambers（CTGC）,the open-top chambers（OTC）are commonly used to control elevated CO₂ concentration for plant science research.In the present study,we aimed to evaluate a modified OTC,designed and constructed based on previous OTC experiences,which provides a precise control of CO₂ under different concentrations,with excellent control of air temperature and humidity.Materials and methods Three parts of OTC chamber structure,control system and monitoring system are improved and upgraded.（1）The modified OTC has a regular octagonal prism structure made of plastic steel 4 mm thick high transmittance glass material,an improvement over the previous system.The structure dimensions are 1.08 m length（diagonal）,of 2.78 m diameter,and the inner and outer height（top）of 2.55 m and 2.10 m,respectively.（2）The monitoring system consisted of CO₂ analyzers,temperature and humidity sensors,and a data acquisition system.（3）The control system is also composed by other features like programmable logic controller,GPRS communication module,a touch screen,a micro-relay,CO₂ pressure reducing valves,solenoid valves,perforated windpipes,and CO₂ cylinders.The OTC control system automatically collects and uploads data every six minutes using a system control coupled to the PI regulation mode（Proportional integral controller）.A linear controller generates deviation monitoring according to a given and an actual output value.The system is also equipped with a GSM communication module connected with the PLC through the Protocol PPI（Point to point interface）to upload all the data to a web server.The OTC control,monitoring system and the data can be accessed in real time through web browser or mobile App,reducing operation costs and allowing environmental variables monitoring.（4）To test the functionality of the modified OTC,Goji berry（Lycium barbarum L.）plants were grown from May to October on 2017 inside the chambers.Real-time data of CO₂ concentration,temperature,and air relative humidity of the chambers were collected.Results As a result,the average CO₂ levels obtained in the chamber during the study period was 369.33μmol·mol^-1 for ambient conditions,while elevated group 1 and group 2 showed concentrations of558.35μmol·mol^-1 and 772.71μmol·mol^-1 respectively.The fluctuation for elevated group 1 ranged from551.82μmol·mol^-1 to 572.40μmol·mol^-1 with a variation amplitude of 20.58μmol·mol^-1.In the elevated group2,the range of CO₂ concentration was from 756.71μmol·mol^-1 to 779.79μmol·mol^-1 with variation amplitude of 23.08μmol·mol^-1.In addition,no significant differences were found in temperature and air relative humidity among the chambers treatments（p>0.05）.Discussion The improved OTC simulation control system can well control the CO₂ concentration to meet the preset concentration requirements.In actual control,it needs to further debug and improve to achieve stable operation.Hysteresis usually occurs in the actual control,mainly because in the actual control,CO₂ sensor from the monitoring of indoor air CO₂ concentration to the control system takes a certain time,the control system automatically adjusts the solenoid valve opening and closing frequency through real-time monitoring data,keeping the CO₂ concentration in the air chamber always close to the preset value,the CO₂ concentration in the air chamber will be higher than the preset value due to the time difference.In addition,the CO₂ concentration is also affected by the outside wind speed and the photosynthetic respiration of the plant,and the CO₂ concentration in the air chamber changes greatly.The main purpose of using OTC simulation system in this study is to long-term study the effects of different CO₂ concentration treatments on the physiological process of plants.The influencing factors are the same except for the CO₂ concentration.This system monitors the temperature and humidity of OTC chambers in real time through different treatment.The results show that the difference in temperature and humidity in different treatment chambers is small,the trend of change is consistent,and the test control effect is good,and the expected purpose of the test is achieved.In addition,if it is necessary to increase temperature simulation in the study,a temperature increase control system may be correspondingly increased to achieve different CO₂ concentration and temperature interactive processing simulation test.Conclusions These results demonstrated precise control of CO₂ concentration,temperature,and humidity inside the modified OTC chambers,showing an excellent development of CO₂ effect improvement on Goji berry,and it can be used to test climate change response in other plant species.Recommendations and perspectives The improved OTC control system realizes automatic unsupervised operation 24 hours a day.All data systems are automatically uploaded to the web server.The system operation status can be monitored in real time through a web browser/mobile phone App,and the system can be controlled and the solenoid valve can be opened and closed.Download data,no geographical restrictions,no manual on-site supervision and save operating costs,improve work efficiency.The system can be used to study the simulation test of plants responding to climate change,and it can also provide reference for other studies related to the simulation of climate change.更多还原