Changes in photosynthesis and carotenoid composition of pepper (Capsicum annuum L.) in response to low-light stress and low temperature combined with low-light stress

Light and temperature are two major factors for plant growth. Carotenoids are important photoprotective and light-harvesting pigments in photosynthetic organs. Therefore, this study explored photosynthesis and carotenoid-related metabolism under control (CK), low-light (L), and low-temperature and low-light (LL) conditions by using the pepper (Capsicum annuum L.) varieties Longjiao 5 and Hangjiao 4. We found the increased inhibition of plant growth and photosynthetic capacity under both L and LL stress. Meanwhile, carotenoid-related metabolic compounds accumulated in pepper showed different responses to the two stresses. Significantly, zeaxanthin contents were 6.69-8.88 times higher under LL than that of CK, alpha-carotene contents were 0.9-2.1 times higher under L than that of CK, which may enhance the tolerance to LL and L. Our findings provide a foundation for further research on the molecular mechanism of carotenoid functions regarding L and LL tolerance by regulating photosynthesis.