Photosynthetic activity and antioxidative defense during cold and freezing stress of the resurrection plants Ramonda nathaliae and Ramonda serbica

Abstract

Ramonda nathaliae and Ramonda serbica belong to the group of resurrection plants, which are capable of restoring normal physiological activity after the desiccation period. Understanding photosynthetic apparatus's response to harsh environmental conditions and evaluating antioxidative levels is essential since it can reveal the mechanisms of their stress tolerance and the strategies for enhancing cold and freezing tolerance. This study examines how cold and freezing temperatures impact photosynthetic activity, chlorophyll fluorescence, total flavonoid and phenol content, antioxidant capacity, as well as the levels of photosynthetic and stress-induced proteins in Ramonda species leaves during autumn and winter in the natural condition. Based on the results obtained, the greatest reduction in CO2 assimilation occurred during freezing stress in comparison to both cold stress and control conditions. The quantum efficiency of photosystem II was slightly affected during cold temperatures but gradually decreased when the temperatures dropped to freezing, reaching minimum values in the desiccated leaves. Significant enhancement in the total phenolic and flavonoid content, as well as increased antioxidant capacity in both Ramonda species during desiccation under freezing stress, helps to protect plants against oxidative damage. Low temperatures decreased the abundance of fundamental photosynthetic proteins, whereas the content of some light-harvesting complex (LHC) proteins was increased. The accumulation of early light-inducible proteins (ELIPs) and dehydrins suggested their role in the acquisition of freezing tolerance. The results show that Ramonda species have developed some biochemical and physiological adaptations that enhance their ability to preserve their photosynthetic processes during cold and freezing temperatures. Findings from this study may contribute to the development of breeding strategies in agriculture, particularly for cold-prone regions, to enhance crop resilience and productivity under challenging environmental conditions.

Keywords

• Antioxidant
• Cold and freezing tolerance
• Dehydration
• Gas exchange
• Chlorophyll fluorescence
• Photosynthetic proteins