From leaf to whole-plant water use efficiency (WUE) in complex canopies: Limitations of leaf WUE as a selection target

摘要: Plant water use efficiency (WUE) is becoming a key issue in semiarid areas, where crop production relies on the of large volumes water. Improving WUE necessary for securing environmental sustainability food these areas. Given that climate change predictions include increases temperature and drought regions, improving mandatory global production. commonly measured at leaf level, because portable equipment measuring gas exchange rates facilitates simultaneous measurement photosynthesis transpiration. However, when those measurements are compared with daily integrals or whole-plant estimates WUE, two sometimes do not agree. Scaling up from single-leaf to was tested grapevines different experiments by comparison instantaneous [ratio between CO2 assimilation (AN) transpiration (E); AN/E] midday AN/E measurements, showing low correlation, being worse increasing stress. We sought evaluate importance spatial temporal variation carbon balances plant levels. The position (governing average light interception) canopy showed marked effect WUE. Night respiration were also evaluated, as well contributions total balance. Two main components identified filling gap whole WUE: gain loss flux losses dark respiration. These results show evaluation among genotypes treatments needs be revised.