Transient response to TPU limitation is lost after acclimation
Plants were tested for transient responses to TPU-limiting conditions before and after a 24-h acclimation to elevated CO2 (Fig 6). For each time-point, plants were given 10 min at ambient CO2 (400 ppm) before pulsing with high CO2 (1500 ppm) at the end of which chlorophyll fluorescence parameters were measured. Time points are scrambled for each plant. Non-adapted plants exhibited a transient reduction of Qa to a minimum of 21% following the introduction of TPU-limiting conditions, resulting in partitioning of energy intoNPQ rather than photochemistry. After adaptation, plants did not exhibit reduction of Qa significantly below the steady-state value in the elevated CO2 environment.