REVIEW PAPER
Cellular light memory, photo-electrochemical and redox retrograde signaling in plants

Plant chloroplasts emit signals that regulate the expression of nuclear-encoded genes, a process known as retrograde

signaling. Environmental stresses, such as rapid and dynamic changes in light intensity and quality, temperature,

relative humidity, water and CO2 availability, cause excess absorption of light energy (EEE) and induce

chlorophyll fluorescence and heat dissipation, which lead to the generation of singlet stages of dioxygen, chlorophyll

and carotenoid molecules. These primary quantum events in photosynthesis induce secondary redox reactions

in photosystems, e.g. electrical charge separation, chloroplast lumen acidification and activation of

the xanthophyll cycle by means of non-photochemical quenching (NPQ), redox reactions between the photosynthetic

electron carriers (electron transport), and formation of reactive oxygen species. These, in turn, induce cascades

of physiologically regulated redox reactions in the chloroplast stroma metabolism that regulate cellular light

memory. Recently published data suggest that plants, with the help of EEE, NPQ, photoelectrochemical-redox

retrograde signaling and cellular light memory, are able to perform biological processing in order to optimize their

photosynthesis, transpiration, light acclimatory and defense responses, and in consequence, their Darwinian

fitness. Understanding of the above-mentioned processes is crucial for future biotechnological amelioration of

crop production.