Study On Nondestructive Testing Technology Of Plant Disease With Acoustic Emission Principle

During the process of their growth, plants are usually subjected to various environmental stresses, including abnormal temperature, lack of moisture, adverse physical and chemical conditions of oil etc. And disease stress is the important factors of limit plant growth and development, gene expression and production. In our country, because of the ecological environment, cultivation technology, plant variety changes as well as the more and more deterioration of plant growth environment, plant diseases have the tendency of becoming more and more serious, and due to the excessive use of pesticides cause environment pollution, which has great threat to our country’s food safety and wood quality.In this topic, the American National Instruments (NI)’s virtual instrument software development platform LabWindows/CVI was used as the system’s development platform, by the acoustic emission technique for the theoretical basis, to explore the mechanism of ultrasonic sound source signal by the state of woody plant stress in the disease. Establishment multi-factor comprehensive mathematical model of the mechanism between the sound source signal and plant disease prediction, disease type, lesion location, extent of disease and transpiration, soil moisture, atmospheric saturation deficit, temperature, light, nutrients, determine the quantitative relationship between source signal and the degree of disease, plant physiological status. On this basis, explore the non-destructive testing of the tree under disease stress.In this system, PCI-2acoustic emission board, R15probes, electronic balance, temperature, humidity, carbon dioxide concentration, illumination intensity sensors and PCI-8333data acquisition (DAQ) card were selected to construct hardware detection system, and virtual instrument technology was utilized to construct software system, the system for real-time acquisition and detection of information between the acoustic emission and diseases stress of crops was studied and developed, and the contrast experiment study was carried out in a greenhouse by taking a healthy tree and a diseases stressed tree as the objectives.The results show that there are a certain physiological cycle laws in the acoustic emission of healthy plant, generally the"double peak area" can appear; but distortion can occur in the acoustic emission of diseases stressed plant, a sharp increase of the acoustic emission frequency can suddenly take place at some time, immediately the plant begins to show disease symptoms, and acoustic emission signals lose the regularity; from the perspective of correlation, there is a certain relevance between the acoustic emission frequency of plants and transpiration rate, temperature, humidity, CO2concentration, illumination intensity. The correlation coefficient of acoustic emission frequency and transpiration rate has certain volatility, and the volatility has a certain plant physiological significance, which can be regarded as an important index pertaining to acoustic emission.By taking these as the theoretical basis, to further determine the relationship between acoustic emission signals and disease degrees and physiological states of plant, and to investigate the scientific management of plants and timely detection of disease, so that all plants reached the theoretical maximum economic, ecological and social benefits。The paper also discusses the diseases forecasting and automatic spraying of pesticide variables of main woody plants, which will become a new approach for the physiological signal detection of crops as well as comprehensive and precise prevention and control of diseases.