Distinct non-photochemical quenching characteristics under constant and fluctuating light conditions: comparison...

To explore the variation in adaptability to fluctuating light environments, the non-photochemical quenching (NPQ) characteristics of a local tobacco variety Xiaofeng 8 and a foreign introduced variety K326, under both constant and fluctuating light conditions were examined. The field experiment demonstrated that Xiaofeng 8 exhibited significantly stronger growth compared to K326, with the dry weight per plant and leaf area of Xiaofeng 8 increased by 28.26 % and 32.85 % compared with those of K326, respectively. Further, a distinct activation pattern of NPQ was detected in both varieties during the transition from dark to high light. Building on this finding, our subsequent tests proved that, in the high light intensity segments of a fluctuating light environment, Xiaofeng 8 exhibited a higher NPQ value compared to K326, indicating an enhanced capacity for dissipating excess light energy as thermal energy and mitigating the potential risk of photodamage. Subsequent analysis of the contents of violaxanthin (V), antheraxanthin (A), and zeaxanthin (Z) within the two varieties after high - light treatment has proved that Xiaofeng 8 has a superior ability to dissipate excess absorbed light energy under high - light conditions. This ability may contribute to its better growth under fluctuating light environments. Mutants defective in violaxanthin de-epoxidase (VDE) and zeaxanthin epoxidase (ZEP) were employed to examine their involvement in regulating plants growth under fluctuating light condition. The results showed that defects in these enzymes affected the NPQ response and reduced the growth rate of the mutants under fluctuating light conditions, suggesting its pivotal role of xanthophyll in regulating plant growth and adaptation to variable light environments. Collectively, these findings emphasize the importance of exploring genetic resources improving plant NPQ under fluctuating light conditions from both domestic and imported varieties, thereby providing promising targets for selecting and breeding new crop varieties with improved yield.