Stress-Induced Buildup of Screening Pigments

Abstract

This chapter extends the discussion of screening pigments with an outline of possible mechanisms for the induction and regulation of their biosynthesis under stresses. Typical patterns of changes in pigment content and composition during the accumulation of screening pigments in plants are presented. Special attention is paid to the role of solar UV radiation in the induction of phenolics (which are admittedly the most ubiquitous and probably most studied screening pigment group) and to photostability of extrathylakoid carotenoids (the screening function of which is being vigorously investigated).As stated in the previous chapter, the pronounced buildup of screening pigment content observed in response to elevated levels of radiation of the corresponding spectral band is a prerequisite for the function of the screening pigment. The patterns of accumulation of different groups of screening pigments in microalgae and higher plants during their acclimation to high fluxes of solar radiation are considered below. However, before proceeding to the discussion, several reservations have to be made. Firstly, there are many works on accumulation of phenolics in leaves and other plant organs induced by natural and artificial UV radiation and the ecological and physiological significance of this phenomenon which are given full credit but could not be cited here in full number owing to space constraints. Therefore, only important trends will be outlined with a minimum of references; for detailed accounts of these experimental works, one may refer to recent reviews in the field (see, e.g., Beggs et al. (1986), Caldwell et al. (2007, Rozema et al. (1997)). Secondly, considerable attention has been paid to accumulation of secondary carotenoids which could serve as screening compounds since much less is known about this phenomenon in comparison with accumulation of phenolics.