.potometer-input-group {
margin-bottom: 20px;
}
.potometer-label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #2c3e50;
}
.potometer-input {
width: 100%;
padding: 12px;
border: 1px solid #d1d9e6;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
transition: border-color 0.2s;
}
.potometer-input:focus {
border-color: #27ae60;
outline: none;
}
.calculate-btn {
background-color: #27ae60;
color: white;
border: none;
padding: 14px 24px;
font-size: 16px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
transition: background-color 0.2s;
}
.calculate-btn:hover {
background-color: #219150;
}
.result-box {
margin-top: 25px;
padding: 20px;
background-color: #ffffff;
border-left: 5px solid #27ae60;
border-radius: 4px;
display: none;
box-shadow: 0 2px 5px rgba(0,0,0,0.05);
}
.result-item {
margin-bottom: 10px;
font-size: 15px;
color: #555;
display: flex;
justify-content: space-between;
align-items: center;
}
.result-value {
font-weight: bold;
color: #2c3e50;
font-size: 18px;
}
.final-rate {
font-size: 24px;
color: #27ae60;
margin-top: 10px;
padding-top: 10px;
border-top: 1px solid #eee;
}
.input-hint {
font-size: 12px;
color: #7f8c8d;
margin-top: 4px;
}
function calculateTranspiration() {
// Get input values
var distance = document.getElementById('bubbleDistance').value;
var time = document.getElementById('timeInterval').value;
var radius = document.getElementById('capillaryRadius').value;
var resultBox = document.getElementById('transpirationResult');
// Convert to floats
var d = parseFloat(distance);
var t = parseFloat(time);
var r = parseFloat(radius);
// Validation
if (isNaN(d) || isNaN(t) || isNaN(r) || t <= 0 || r <= 0 || d < 0) {
alert("Please enter valid positive numbers for all fields. Time and Radius must be greater than zero.");
return;
}
// Calculation Logic
// 1. Calculate Area of the capillary tube (Circle Area = π * r²)
var area = Math.PI * Math.pow(r, 2);
// 2. Calculate Volume of water uptake (Cylinder Volume = Area * height/distance)
// Result is in cubic millimeters (mm³), which is equivalent to microliters (µL)
var volume = area * d;
// 3. Calculate Rate (Volume / Time)
var rate = volume / t;
// Display Results
resultBox.style.display = "block";
// Format numbers
document.getElementById('displayArea').innerHTML = area.toFixed(4) + " mm²";
document.getElementById('displayVolume').innerHTML = volume.toFixed(2) + " mm³ (µL)";
document.getElementById('displayRate').innerHTML = rate.toFixed(3) + " mm³/min";
}
Potometer Transpiration Rate Calculator
The linear distance the bubble traveled along the scale.
The duration of the observation.
Usually between 0.5mm and 1.0mm for standard lab potometers.
Cross-Sectional Area:
–
Total Water Volume Uptake:
–
Transpiration Rate:
–
Understanding Potometer Calculations
A potometer is a device used in plant physiology to measure the rate of water uptake by a leafy shoot. While water uptake is not exactly equal to the rate of transpiration (since some water is used for photosynthesis and turgidity), the difference is negligible (usually less than 2%), making the potometer an excellent tool for estimating transpiration rates.
How the Math Works
The calculation treats the capillary tube of the potometer as a cylinder. To find the volume of water lost (which corresponds to the movement of the air bubble), we calculate the volume of that cylinder.
- Step 1: Calculate Cross-Sectional Area ($A$)
Using the radius ($r$) of the capillary tube, we use the formula for the area of a circle:
$A = \pi r^2$ - Step 2: Calculate Volume ($V$)
Multiply the cross-sectional area by the distance ($d$) the air bubble moved:
$V = \pi r^2 \times d$ (Volume in $mm^3$ or $\mu L$) - Step 3: Calculate Rate
Divide the total volume by the time taken ($t$) to get the rate:
$Rate = \frac{V}{t}$
Practical Example
Suppose you are conducting an experiment to test the effect of wind speed on a plant shoot. You observe the following:
- The capillary tube has a radius of 0.5 mm.
- The air bubble moves 25 mm along the scale.
- This movement takes 10 minutes.
The Calculation:
- Area = $3.14159 \times 0.5^2 = 0.7854$ mm²
- Volume = $0.7854 \times 25 = 19.635$ mm³
- Rate = $19.635 / 10 = 1.96$ mm³/min
Factors Affecting Transpiration Rate
When using this calculator for lab reports or analysis, consider how environmental factors influence the input values (Distance per Time):
- Light Intensity: Increases stomatal opening, increasing the rate.
- Temperature: Higher temperatures increase evaporation and diffusion rates.
- Humidity: High humidity reduces the concentration gradient, slowing down the rate.
- Wind Speed: Removes the boundary layer of water vapor, increasing the rate.