Editorial: Chlorophyll fluorescence analysis in biotic and abiotic stress, volume II
Michael Moustakas, Lucia Guidi, Ángeles Calatayud
Abstract
Chlorophyll fluorescence analysis in biotic and abiotic stress, volume II Chlorophyll a fluorescence emission results from absorbed light energy that is not dissipated as heat or not used for photosynthetic reactions in plants. Photosynthesis is allocated into two distinct parts, the light reactions and the carbon dioxide (CO 2 ) fixation. In the light reactions, light energy is utilized to generate an oxidized protein complex capable of extracting electrons from water at photosystem II (PSII), and at the same time re-energizing the extracted electron to reduce NADP + at photosystem I (PSI). These 'light harvesting' reactions result in the formation of ATP and reducing power (reduced ferredoxin and NADPH), and subsequent CO 2 fixation through the Calvin-Benson-Bassham cycle. Chlorophyll a fluorescence analysis can determine the amount of absorbed light energy that is directed to photochemistry and estimates photosynthetic efficiency under biotic or abiotic stresses Chlorophyll a fluorescence signals can be interpreted in terms of photosynthetic activity to obtain information about the state of the photosynthetic apparatus and especially of photosystem II (PSII) Measurements of chlorophyll a fluorescence have been extensively used to probe the function of the photosynthetic machinery and for screening different crops for plant tolerance to numerous stresses, and nutritional requirements The use of the pulse amplitude modulation (PAM) method can principally calculate the amount of absorbed light energy that is directed to PSII for photochemistry, which is dissipated as heat through the non-photochemical quenching (NPQ) mechanism or dissipated by less well characterized non-radiative fluorescence processes, that are marked as F PSII , F NPQ , and F NO , respectively, with the sum of them to be equal to one