Transpiration is fastest when humidity is low and temperature is high, but in some plants it seems to increase in response to light as well. During one 12-hour period when cloud cover and light intensity varied frequently, a scientist studying a certain crop plant recorded the data in the table (top right). (The transpiration rates are grams of water per square meter of leaf area per hour.)
Do these data support the hypothesis that the plants transpire more when the light is more intense?
If so, is the effect independent of temperature and humidity?
Explain your answer. (Hint: Look for overall trends in each column, and then compare pairs of data within each column and between columns.)

Verified step by step guidance

1. Step 1: Begin by analyzing the data in the table. Look at the columns for light intensity and transpiration rate to identify any trends. Specifically, check if higher light intensity correlates with higher transpiration rates.
2. Step 2: Compare pairs of data within the light intensity and transpiration rate columns. For example, at 12 PM, light intensity is 88% and the transpiration rate is 161 g/m²·hr, while at 7 AM, light intensity is 8% and the transpiration rate is 45 g/m²·hr. This suggests a potential relationship between light intensity and transpiration rate.
3. Step 3: Examine the temperature and humidity columns to determine if these factors also influence transpiration rate. For instance, at 1 PM, the temperature is 33°C and humidity is 65%, with a transpiration rate of 199 g/m²·hr, while at 6 PM, the temperature is 18°C and humidity is 80%, with a transpiration rate of 78 g/m²·hr. This indicates that temperature and humidity may also play a role.
4. Step 4: Compare data across columns to assess whether the effect of light intensity on transpiration rate is independent of temperature and humidity. For example, at 10 AM, light intensity is 58%, temperature is 21°C, and humidity is 86%, with a transpiration rate of 83 g/m²·hr, while at 4 PM, light intensity is 50%, temperature is 29°C, and humidity is 69%, with a transpiration rate of 137 g/m²·hr. This suggests that light intensity interacts with temperature and humidity.
5. Step 5: Conclude by summarizing the trends observed. The data support the hypothesis that plants transpire more when light intensity is higher, but the effect is not entirely independent of temperature and humidity, as these factors also influence transpiration rates.

Key Concepts

Transpiration

Transpiration is the process by which plants lose water vapor through small openings called stomata, primarily located on the leaves. This process is influenced by environmental factors such as temperature, humidity, and light intensity. Higher temperatures typically increase transpiration rates due to increased evaporation, while lower humidity can enhance the water vapor gradient, promoting more water loss.

Environmental Factors

Environmental factors such as temperature, humidity, and light intensity play crucial roles in regulating transpiration rates. High temperatures can increase the rate of water evaporation from leaf surfaces, while low humidity levels create a greater difference in water vapor concentration between the inside of the leaf and the surrounding air, leading to increased transpiration. Light intensity affects stomatal opening, which can also influence transpiration rates.

Data Analysis

Data analysis involves examining the recorded transpiration rates in relation to varying environmental conditions to identify trends and correlations. By comparing the transpiration rates across different levels of light intensity, temperature, and humidity, one can determine if there is a significant relationship between these variables. This analysis is essential for validating hypotheses regarding plant behavior under varying environmental conditions.