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

Abstract

Canopy photosynthesis (A_c), rather than leaf photosynthesis, is critical to gaining higher biomass production in the field because the daily or seasonal integrals of A_c 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. This system can also be used to measure the fluxes of greenhouse gases when integrating with CH₄ and N₂O analyzers. Here, we describe the protocol for 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.

Keywords: Automatic canopy chamber; CAPTS; Canopy photosynthesis; Canopy respiration; Canopy transpiration; Gas exchange; Rice; Tobacco; Wheat.