Biology – Homeostasis in plants | e-Consult

Experimental Design:

The student could use the following experimental design:

• Independent Variable: Light intensity (e.g., measured in lux or using a light meter). The student would need to have several different light intensity treatments.
• Dependent Variable: Rate of transpiration. This can be measured using a transpiration apparatus (e.g., a potometer or a weighing method).
• Control Variables: These are factors that must be kept constant across all treatments to ensure that only the light intensity is affecting the rate of transpiration. Important control variables include:

• Plant species (use the same species of plant for all treatments)
• Plant size (use plants of similar size)
• Temperature (maintain a constant temperature)
• Humidity (maintain a constant humidity)
• Air movement (minimize air movement around the plants)
• Pot size and type (use the same pots for all treatments)
• Soil type (use the same soil for all treatments)

Measuring Transpiration Rate:

The transpiration rate can be measured using a potometer or a weighing method:

• Potometer: A potometer is a device that measures the rate of water uptake by a plant. A leaf is placed in a sealed tube, and the water level in the tube is measured over time. The decrease in water level indicates the rate of transpiration.
• Weighing Method: The plant is weighed at the start and end of the experiment. The difference in mass (water lost) is used to calculate the transpiration rate.

Expected Results and Conclusion:

The student would likely find that the rate of transpiration increases with increasing light intensity, up to a certain point. This is because light stimulates stomatal opening, which increases CO2 uptake and transpiration. However, at very high light intensities, the rate of transpiration may plateau or even decrease slightly due to other factors becoming limiting (e.g., water availability).

Supporting the Statement:

The results of this experiment would strongly support the statement that stomata respond to changes in environmental conditions. The observed increase in transpiration rate with increasing light intensity demonstrates that stomatal opening is regulated by light. This regulation is a crucial adaptation that allows plants to optimize CO2 uptake for photosynthesis while minimizing water loss, thereby ensuring their survival in a variety of environments. The experiment highlights the link between environmental cues (light) and physiological responses (stomatal opening) in plants.