concept

transpiration efficiency

Also known as: transpiration efficiencies

Facts (10)

Sources

The Ecology of Photosynthetic Pathways | Learn Science at Scitable nature.com Nature 10 facts

claimCAM photosynthetic plants have higher transpiration efficiencies than C3 or C4 plants because they open their stomata at night when vapor pressure differences between the leaf and surrounding air are lowest.

claimPlants regulate intercellular CO2 concentration (Ci) through physiological responses to the environment; increased stomatal restriction of CO2 diffusion lowers Ci, which leads to higher transpiration efficiency (A/E).

claimThe difference between internal leaf vapor pressure (VPi) and ambient vapor pressure (VPa) is largest when temperatures are high and the air is dry, making it difficult for plants to achieve high transpiration efficiency in these environments.

claimTranspiration efficiency is a function of the CO2 concentration gradient (Ca - Ci), where ambient CO2 concentrations (Ca) are relatively constant, but intercellular CO2 concentration (Ci) is determined by the balance between CO2 supply through the stomata and CO2 uptake by photosynthesis.

claimBecause PEP carboxylase has a higher affinity for carbon dioxide, C4 plants can operate efficiently at low intercellular carbon dioxide concentrations, allowing for lower stomatal conductance, decreased transpiration, and increased transpiration efficiency.

claimHigh intercellular CO2 concentration (Ci) is associated with low transpiration efficiency (A/E), while low Ci is associated with high A/E, assuming constant vapor pressure differences.

claimTranspiration efficiency (A/E) is partially determined by the environment, specifically the vapor pressure gradient (VPa - VPi); a larger gradient between the vapor pressure inside the leaf and the surrounding air results in lower transpiration efficiency.

claimTranspiration efficiency is defined as the ratio of photosynthesis to transpiration (A/E) and serves as a measure of a plant's success in balancing carbon gain with water loss.

claimHigh transpiration efficiency in plants is often associated with slow growth and low photosynthetic rates because restricting CO2 diffusion limits both photosynthesis and transpiration.

formulaTranspiration efficiency (A/E) is calculated using the formula: A/E = (Ca - Ci)/1.6 (VPa - VPi), where Ca is ambient CO2 concentration, Ci is intercellular CO2 concentration, VPa is ambient vapor pressure, and VPi is internal leaf vapor pressure.