Figure 2. The procedure of photosynthetic induction state measurements under different durations of exposure to a low light level.

Photosynthesis of the leaves was first fully induced by a prolonged light-saturated condition (n > 15, PPFD = 1500 μmol m⁻² s⁻¹), then the data were automatically recorded every 2 s. Three minutes after recording, the light was decreased immediately to 100 μmol m⁻² s⁻¹. After each low-light phase, the light was increased immediately to 1500 μmol m⁻² s⁻¹ for the leaves to be fully induced again (5, 10, and 15 min were required, respectively). There were a total of four low-light durations (1, 5, 10, and 30 min). PPFD, photosynthetic photon flux density.