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At present, the methods for measuring plant water potential mainly include: small liquid flow method, weight measurement water potential method, plasmolysis method to measure osmotic potential, pressure chamber method and water pressure method, thermocouple hygrometer method and dew point method. Among them, the thermocouple hygrometer method and the dew point method require less samples and are less affected by external environmental conditions, and are commonly used internationally. The plant water potential pressure chamber is a widely used instrument in recent years and it is also relatively accurate and simple.
The plant water potential pressure chamber obtains the water potential of the blade by measuring the relative humidity. When the water potential instrument is working, the host computer is connected with the sensor. The sensor clamps the blade and forms a closed environment. A node of the thermocouple on the sensor is installed in the upper part of the sample chamber and passes through. Cooling causes the moisture in the closed leaf chamber to condense and evaporate after being warmed. The heat is taken away to maintain the temperature at the dew point, and the internal environment appears stable for a short time. The relative water content in the stable time is used to obtain the water potential of the blade. When measuring, first use the data control system to set the parameters of the source, data storage, sampling mode, sensor line coefficient. After starting the scan, the control system applies a reverse current of 8 mA to the thermocouple to cool the thermocouple junction in the sample chamber. When the temperature drops below the dew point, a small amount of liquid water will condense on the surface of the junction. Current. At the beginning, the junction temperature rises rapidly due to heat exchange equilibrium; subsequently, the surface moisture evaporates away, leaving its temperature at the dew point, showing a short-term equilibrium state; after the water evaporation on the surface of the junction is completed, The temperature will rise again until it returns to ambient temperature.
Based on the introduction of water potential measurement technology, this study has optimized and developed the plant water potential pressure chamber, which has improved the interface, storage capacity and data output methods. Through the determination of the diurnal variation of leaf water potential of four plant species, the results obtained from plant water potential stress chamber have a good linear correlation, and the correlation coefficient is greater than 0.98, and the difference is not significant (P<0.001). This shows that the performance of the plant water potential pressure chamber is up to the level of imported water potential meter and can meet the requirements of water potential measurement.
Study on the Performance of Plant Water Potential Chamber
Water potential is one of the important indicators of the physiological characteristics of plant water. Affected by the combined effects of soil, vegetation, and atmospheric conditions, plant water potential plays an extremely important role in the water transport process of SPAC. In general, the lower the plant tissue water potential is, the stronger the water absorption capacity is, and conversely, the weaker water absorption capacity is, so that the degree of drought and drought resistance of the plant can be determined. In the absence of water resources, water potential is often used as a sensitive indicator to determine plant water deficit. In the water potential of various parts of the plant, the leaf water potential most represents the energy level of the plant water movement and is a direct manifestation of the tissue water status, which determines the water absorption capacity of the plant root system and the canopy's transpiration rate, reflecting the plant's growth season. This kind of physiological activity is constrained by the environmental moisture conditions. The study of plant water potential, especially leaf water potential, has important theoretical significance and application value for revealing the laws of water movement and their mutual relations in SPAC. The application of plant water pressure chambers is liked under such conditions.