The pressure chamber method plant water potential meter is an important tool for measuring the water status of plants. Its operation core is to gradually increase the pressure to cause liquid droplets to appear at the incision of plant leaves or branches. The pressure value at this time is the plant water potential (usually negative). The following are the detailed operation steps:
1、 Preparation before operation: Ensure the equipment and sample are in good condition
Sample collection and processing
Select representative leaves, branches, or petioles of plants (to avoid diseased or damaged leaves), quickly cut them with scissors during sampling. If in vitro testing is required, immediately wrap the incision with moist gauze (to prevent water loss) and avoid direct sunlight.
If measuring the whole leaf, retain the petiole; If measuring branches, keep a section with leaves (length adapted to the pressure chamber chamber), remove excess tissue at the incision site, and ensure a smooth incision.
Equipment inspection
Check the sealing performance of the pressure chamber: Close the exhaust valve, manually increase the pressure to a certain value (such as 0.5MPa), observe whether the pressure is stable, and if it drops rapidly, repair the sealing ring.
Prepare accessories: Choose a suitable sample chamber based on the sample size (such as a small diameter chamber for leaves and a large diameter chamber for branches), a sealing ring (to ensure a tight fit with the sample), and a magnifying glass (to observe droplets).
2、 Post operation processing: equipment maintenance and data organization
Equipment cleaning
After each use, clean the plant debris in the chamber, wipe the sealing ring and chamber wall with a dry cloth to avoid residual juice from corroding the equipment.
When not in use for a long time, release the pressure to 0 and store in a dry and ventilated place. Store the sealing ring separately to prevent aging.
Data calibration and repetition
Measure the same part of the same plant at least 3 times and take the average to reduce errors.
If there is doubt about the accuracy of the reading, the sample can be replaced for retesting, or the equipment can be calibrated with a standard solution (such as a known concentration of sucrose solution) (the water potential of the standard solution can be calculated using a formula and verified by comparing it with the measured value).
3、 Key principle: Avoid water loss and errors
Quick operation: From sampling to sample loading, try to complete it within 5 minutes to reduce the evaporation of water in the ex vivo sample.
Stable pressure rate: The pressure rate of different samples (such as fresh and wilted leaves) can be fine tuned, but the same set of experiments needs to be consistent to ensure data comparability.
Environment consistency: When conducting measurements, try to do so under the same temperature and humidity conditions as the sampling environment (such as avoiding direct air conditioning on the sample for indoor measurements).
Summary: The core is to accurately capture the initial moment of liquid droplets
The key to the pressure chamber method is to accurately determine the pressure value of the first droplet appearing at the incision site through stable pressurization, which directly reflects the degree of plant water stress (the higher the pressure, the lower the water potential, and the more water deficient the plant is). During operation, attention should be paid to sample freshness, equipment sealing, and observation detail in order to obtain reliable water potential data, which can provide a basis for plant drought resistance research, irrigation management, etc.