Measuring and Quantifying Characteristics of the Post-illumination Burst

Leaf-level gas exchange enables accurate measurements of net CO₂ assimilation in the light, as well as CO₂ respiration in the dark. Net positive CO₂ assimilation in the light indicates that the gain of carbon by photosynthesis offsets the photorespiratory loss of CO₂ and respiration of CO₂ in the light (R_L), while the CO₂ respired in the dark is mainly attributed to respiration in the dark (R_D). Measuring the CO₂ release specifically from photorespiration in the light is challenging since net CO₂ assimilation involves three concurrent processes (the velocity of rubisco carboxylation; v_c, velocity of rubisco oxygenation; v_o, and R_L). However, by employing a rapid light-dark transient, it is possible to transiently measure some of the CO₂ release from photorespiration without the background of v_c-based assimilation in the dark. This method is commonly known as the post-illumination CO₂ burst (PIB) and results in a "burst" of CO₂ immediately after the transition to the dark. This burst can be quantitatively characterized using several approaches. Here, we describe how to set up a PIB measurement and provide some guidelines on how to analyze and interpret the data obtained using a PIB analysis application developed in R.