Some carotenoids function in NPQ and directly quench ROS such as singlet oxygen (Baroli et al., 2000). Importantly, a strong correlation between zeaxanthin accumulation and a rapidly inducible form of NPQ, known as energy-dependent quenching (qE; Horton et al., 1996; Niyogi, 2000), has been demonstrated in several tracheophyte species (Demmig-Adams, 1990; Demmig-Adams and Adams, 1996). Sustained NPQ mechanisms, often referred to as photoinhibitory quenching (qI), result in a decrease in the quantum efficiency of photosynthesis and can also be associated with zeaxanthin, though possibly through a different, pH-independent mechanism (Verhoeven et al., 1996). Desert plants might be expected to undergo the qE form of NPQ for diurnal fluctuations in light intensity as well as qI or other sustained NPQ forms, e.g. qH (MalnoĆ«, 2018), to deal with seasonal changes in light. Indeed, desiccation-tolerant mosses have been shown to exhibit strong, sustained mechanisms of NPQ after exposure to high light or desiccation (Yamakawaet al., 2012; Yamakawa and Itoh, 2013).