Recovery of photosynthetic activity of resurrection plant Haberlea rhodopensis from drought- and freezing-induced desiccation

The recovery of photosynthetic activity during rehydration of Haberlea rhodopensis from drought- and freezing-induced desiccation were investigated. The water uptake during the initial 15 h was slow thus preventing cellular damages. The results showed faster recovery of quantum efficiency of PSII in plants rehydrated after freezing stress (RAF) compared to plants rehydrated after drought stress (RAD) and the most significant differences between them were evident after 9-15 h of rehydration. Following rehydration, PSI activity recovered faster compared to PSII and in contrast to PSII, its activity was higher in RAD compared to RAF plants. During the first hours of rehydration, prominent alterations in energy transfer between photosynthetic complexes occurred as revealed by 77 K fluorescence of isolated thylakoids. High proportion of thermal energy dissipation in dry plants and during the first hours of rehydration protects them from photooxidation; the role of PSII reaction center quenching during the recovery was suggested.