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VPD Equation:
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Vapor Pressure Deficit (VPD) is the difference between the amount of moisture in the air and how much moisture the air can hold when it's saturated. It's a crucial measurement in plant physiology and greenhouse management.
The calculator uses the VPD equation:
Where:
Explanation: The equation calculates the difference between the water vapor pressure at the leaf surface and the water vapor pressure in the surrounding air.
Details: VPD is critical for understanding plant transpiration rates, managing greenhouse environments, and optimizing plant growth conditions. It helps prevent both excessive water loss and fungal diseases.
Tips: Enter SVP at leaf temperature and air temperature in kPa, and relative humidity in percentage (0-100%). All values must be valid positive numbers.
Q1: What is a good VPD range for plants?
A: Optimal VPD ranges vary by plant species and growth stage, but generally 0.8-1.2 kPa is good for vegetative growth, while 1.0-1.5 kPa is better for flowering.
Q2: How does VPD affect plant transpiration?
A: Higher VPD increases transpiration as the gradient between leaf and air moisture increases, while lower VPD reduces transpiration.
Q3: What's the relationship between VPD and stomatal opening?
A: Plants typically close stomata at very high VPD to prevent excessive water loss, which can reduce photosynthesis.
Q4: How do temperature and humidity affect VPD?
A: Higher temperatures increase SVP, raising VPD at constant RH. Higher RH decreases VPD at constant temperature.
Q5: Why use leaf temperature instead of air temperature?
A: Leaf temperature often differs from air temperature due to transpiration and radiation effects, making it more accurate for VPD calculations.