Transpiration Rate Calculator
Calculate the rate of water loss per unit time and leaf surface area.
Volume absorbed by potometer or mass lost (1g ≈ 1mL).
Required for calculating rate per unit area.
Calculation Results
Basic Transpiration Rate:
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Hourly Rate:
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Rate per Unit Area:
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Hourly Rate per Area:
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What is Transpiration Rate?
Transpiration is the biological process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. The transpiration rate measures how quickly this water loss occurs over a specific period.
Understanding this rate is crucial in botany, agriculture, and environmental science to determine plant health, water efficiency, and physiological responses to environmental stressors.
How to Calculate Transpiration Rate
The calculation depends on whether you are measuring the total water uptake (using a potometer) or measuring mass loss (gravimetric method). The fundamental formula is:
Rate (R) = Volume of Water Lost (V) / Time (t)
Input Variables Explained:
- Water Loss (mL): The volume of water transpired. If using a potometer, this is the volume of water uptake. If weighing a potted plant, 1 gram of mass loss is approximately equal to 1 mL of water loss.
- Time (minutes): The duration over which the measurement was taken.
- Leaf Surface Area (cm²): The total area of the leaves involved. This is used to normalize the data, allowing comparison between plants of different sizes.
Formulas Used in This Calculator
This calculator performs two levels of analysis:
- Absolute Rate:
Rate = Volume / Time (Result in mL/min) - Relative Rate (per unit area):
Ratearea = Volume / (Time × Area) (Result in mL/min/cm²)
Factors Affecting Transpiration
Several environmental factors influence the rate at which plants lose water:
- Light Intensity: Stomata open in the light to allow gas exchange for photosynthesis, increasing transpiration.
- Temperature: Higher temperatures increase the rate of evaporation and the water holding capacity of the air, increasing transpiration.
- Humidity: High humidity reduces the concentration gradient of water vapor between the leaf interior and the atmosphere, slowing down transpiration.
- Wind Speed: Wind removes the boundary layer of moist air around the leaf, increasing the rate of transpiration.
Example Calculation
Imagine a student uses a potometer to measure water uptake in a leafy shoot.
- Water Uptake: 0.8 mL
- Time Elapsed: 20 minutes
- Leaf Area: 40 cm²
Step 1: Calculate Basic Rate
Rate = 0.8 mL / 20 min = 0.04 mL/min
Step 2: Calculate Rate per Area
Ratearea = 0.8 / (20 × 40) = 0.001 mL/min/cm²