The correct option is
C. the shoot lost 1g of water per hour.
Detailed Explanation:
- Understanding the Setup:
-
A potometer is an apparatus used to measure the rate of water uptake by a plant shoot. In this case, we have a leafy shoot placed in a potometer, and we are measuring its weight before and after a certain period (one hour).
-
Initial and Final Weights:
- The initial weight of the shoot is 18.9g.
- After one hour, the weight of the shoot is 17.9g.
-
To find out how much weight the shoot has lost, we subtract the final weight from the initial weight:
[
\text{Weight lost} = \text{Initial weight} - \text{Final weight} = 18.9g - 17.9g = 1.0g
]
-
Interpreting the Weight Loss:
-
The weight loss of 1.0g indicates that the shoot has lost this amount of water. In plants, water loss can occur through processes such as transpiration, where water evaporates from the leaf surfaces.
-
Why Option C is Correct:
- Since the shoot lost 1g of water over the course of one hour, we can conclude that the shoot lost 1g of water per hour. This is a direct interpretation of the weight change observed.
Why the Other Options are Incorrect:
- Option A: the shoot absorbed 1g of water per hour:
-
This option is incorrect because the weight of the shoot decreased, indicating that it did not absorb water; rather, it lost water. If the shoot had absorbed water, we would expect the weight to increase, not decrease.
-
Option B: 1g of water per hour evaporates from the potometer:
-
This option is misleading. While it is true that water can evaporate from the potometer, the weight loss we observed is specifically due to the water lost by the shoot itself. The potometer's water level may decrease, but we cannot directly conclude that it lost exactly 1g of water per hour without additional data on the potometer's water level.
-
Option D: the potometer water receded at the rate of 1g per hour:
- Similar to option B, this statement cannot be confirmed with the information given. The weight loss of the shoot does not directly indicate the rate at which the water in the potometer receded. The water level in the potometer could be influenced by other factors, such as evaporation from the potometer itself or the water uptake by the shoot.
Summary:
- The shoot lost 1g of water over one hour, indicating a loss rather than an absorption.
- The correct interpretation of the weight change is crucial in understanding plant water dynamics.
- The other options misinterpret the data or make assumptions that are not supported by the observed weight change.
Revision Summary:
- A potometer measures water uptake by plants.
- Weight loss of the shoot indicates water loss, not absorption.
- The correct answer is that the shoot lost 1g of water per hour.
- Misinterpretations can lead to incorrect conclusions about plant water dynamics.