Final answer:
The ratio of carbon fixed through photosynthesis to the amount of water lost via transpiration is known as the water-use efficiency. This efficiency demonstrates how plants balance the need for carbon gains against the loss of water, which varies among different plant species and environments.
Step-by-step explanation:
The ratio of carbon fixed (photosynthesis) per unit of water lost (transpiration) is called the water-use efficiency. In the context of plant biology, water-use efficiency is crucial for understanding how plants manage their resources, especially in varying environmental conditions. Plants like the potato example provided show photosynthetic efficiency by converting sunlight into stored chemical energy, represented in the form of carbohydrates. However, this efficiency is influenced by factors such as water availability, CO2 concentration, and stomatal behavior. For example, C3, C4, and CAM plants have adapted their carbon fixation pathways to optimize water use and carbon gain in different environments. Therefore, understanding water-use efficiency helps in grasping how plants balance their need for carbon through photosynthesis with the inevitable loss of water through transpiration.