A High-Five for High Light Protection

Abstract

Plants cannot live without light, but they also cannot live with too much light. Beyond a certain threshold, a high light intensity will damage the photosynthetic apparatus directly. Furthermore, high light leads to the production of reactive oxygen species that can cause widespread damage in the cell (Li et al., 2009). One way in which plants respond to high light stress is by converting some of the excess light into heat via nonphotochemical quenching (NPQ; Müller et al., 2001). Outdoors, light intensities can vary greatly in time and space: one part of the plant can experience high light stress while another part is shaded. This shaded part of the plant might experience high light stress later on; therefore, it is advantageous for plants to have evolved a systemic signaling response to local high light stress that primes the whole plant to respond better to high light (Karpinski et al., 1999). Several ideas of how the plant transduces such a systemic signal have been postulated, such as a calcium or reactive oxygen species wave and abscisic acid synthesis (Gilroy et al., 2016; Devireddy et al., 2018). However, no direct links between these signaling mechanisms and NPQ systemic high light acclimation have been identified.