Regulations of Photosynthesis under High-Frequency Light Fluctuations
The light-saturated rate of photosynthesis under constant light can be increased by incubations under high-frequency (1 Hz) fluctuating light and dark cycles. Experimental results for the red alga Chondrus crispus suggest that this effect of fluctuating light can be attributed to increased rates of electron transport during the light interval and to post-illumination carbon fixation during the dark. Mathematical model simulations, which incorporate the key biochemical reactions in photosynthesis, also predicted enhanced photosynthetic rates under fluctuating light. It is suggested that fluctuating light effects, by acting at the level of the photosynthetic apparatus, may be a general phenomenon that stimulates photosynthesis by alleviating the rate limitation imposed by carbon metabolism under constant saturating light.