Measuring Canopy Gas Exchange Using CAnopy Photosynthesis and Transpiration Systems (CAPTS).

Canopy photosynthesis (Ac), rather than leaf photosynthesis, is critical to gaining higher biomass production in the field because the daily or seasonal integrals of Ac correlate with the daily or seasonal integrals of biomass production. The canopy photosynthesis and transpiration measurement system (CAPTS) was developed to enable measurement of canopy photosynthetic CO2 uptake, transpiration, and respiration rates. CAPTS continuously records the CO2 concentration, water vapor concentration, air temperature, air pressure, air relative humidity, and photosynthetic photon flux density (PPFD) inside the chamber, which can be used to derive CO2 and H2O fluxes of a canopy covered by the chamber. Here we describe the protocol of using CAPTS to perform experiments on rice (Oryza sativa L.) in paddy field, wheat (Triticum aestivum L.) in upland field, and tobacco (Nicotiana tabacum L.) in pots.