Beyond Photosynthetic Active Radiation: The Role of Far-Red Energy and Signalling in the Improvement of Photosynthesis

Photosynthetic organisms utilise the energy of light for the production of photochemical energy, whereas light signals are perceived by photoreceptors to synchronise the cellular processes with environmental conditions. When plants are exposed to excess light, photoprotective mechanisms are activated to tune up light harvesting and dissipation according to the genetic and metabolic capacity of the photosynthetic apparatus. These mechanisms are affected by the growth light composition. Recent evidence suggests that far-red light energy and signalling impose regulatory effects on photoprotective mechanisms. As a result of the exclusion of far-red light from the definition of photosynthetically active radiation, far-red wavelengths remained largely overlooked in photosynthesis research until recently. Nevertheless, current research has unravelled the specific role of far-red spectra in the regulation of several photoprotective mechanisms, which proposes possible links between light perception and photoprotection. In this regard, the review explores and discusses the current scientific understanding of the role of far-red photon energy in redox signalling and photoprotection in plants.