Responses of the photosynthetic apparatus of Abies koreana to drought under different light conditions

The threat of drought to trees is predicted to increase due to global warming. In a forest stand, the physiological responses of trees can differ depending on the light conditions. We analyzed photosynthetic rate, photopigment, and chlorophyll a fluorescence transient (OJIP test) of Abies koreana E.H. Wilson, under different light (full sunlight and 35 and 75% shading) and water conditions (well-watering, W; and no-watering, NW) to examine the combined effect of light and water. After 21 days of no-watering, we observed decreases in the photosynthetic rate and photopigment contents and quality, impairment of electron transfer from primary to secondary quinone acceptor, inactivation of reaction center, and lower photosynthetic performance index, especially under full sunlight. The time required for recovery after re-watering was also slower under full sunlight. In conclusion, the adverse effects of drought on light absorption and utility of A. koreana in the photosynthetic process were much greater under high light intensity compared to shading conditions, which alleviated these effects.