Optical screening of excessive and potentially harmful solar radiation is an important photoprotective mechanism, though it has received much less attention in comparison with other systems preventing photooxidative damage to photoautotrophic organisms. This photoprotection in the form of screening appears to be especially important for juvenile and senescing plants as well as under environmental stresses-i.e. in situations where the efficiency of enzymatic ROS elimination, DNA repair and other 'classical' photoprotective systems could be impaired. This book represents an attempt to develop an integral view of optical screening-based photoprotection in microalgae and higher plants. Towards this end, the key groups of pigments involved in the screening of ultraviolet and visible components of solar radiation in microalgae and higher plants, and the patterns of their accumulation and distribution within plant cells and tissues, are described. Special attention is paid to the manifestations of screening pigment accumulation in the optical spectra of plants. It is also demonstrated that understanding these effects and their relationships to screening pigments' makeup and spectroscopy in plants provides valuable insights into the state of plants' long-term photoacclimation, as well as ample opportunities for the non-destructive quantification of screening pigments and the assessment of the efficiency of photoprotection providing by these pigments in situ.

1;Preface;8 2;Acknowledgements;10 3;Contents;12 4;Chapter 1: Optical Screening as a Photoprotective Mechanism;15 4.1;References;20 5;Chapter 2: Screening Pigments: General Questions;23 5.1;2.1 The Specificity of the Screening Pigments´ Function;23 5.2;2.2 The Evolution of Screening Pigments in Plants;25 5.3;2.3 The Diversity of Screening Pigments;27 5.3.1;2.3.1 Mycosporin-Like Amino Acids;28 5.3.2;2.3.2 Phenolic Compounds;29 5.3.3;2.3.3 Betalains;32 5.3.4;2.3.4 Carotenoids;33 5.3.5;2.3.5 Other Screening Pigments;37 5.4;2.4 Concluding Remarks;37 5.5;References;39 6;Chapter 3: Stress-Induced Buildup of Screening Pigments;47 6.1;3.1 Buildup of Mycosporine-Like Amino Acid and Phenolic Sunscreens;48 6.1.1;3.1.1 Induction and Regulation of the Synthesis of Mycosporine-Like Amino Acids;49 6.1.2;3.1.2 Induction of Biosynthesis of Phenolic Compounds;49 6.1.3;3.1.3 Accumulation of Different Phenolic Compounds in Response to Strong Solar Irradiation;51 6.2;3.2 Accumulation of Screening Pigments as a Result of Carotenogenesis;57 6.2.1;3.2.1 Carotenogenesis in Microalgae;57 6.2.2;3.2.2 Carotenogenesis in Higher Plants;64 6.3;3.3 Concluding Remarks;72 6.4;References;72 7;Chapter 4: Localization of Screening Pigments Within Plant Cells and Tissues;81 7.1;4.1 Subcellular Localization of Screening Pigments in Plants: General Patterns;81 7.2;4.2 Distribution of Phenolic Screening Compounds Within Plant Tissues;83 7.2.1;4.2.1 Screening Phenolics in the Cuticle;83 7.2.2;4.2.2 Vacuolar Phenolics of Mesophyll and Epidermis;84 7.2.3;4.2.3 Phenolics in Hairs and Trichomes;88 7.3;4.3 Depots of Secondary Carotenoids in Microalgae and Higher Plants;89 7.4;4.4 Concluding Remarks;95 7.5;References;97 8;Chapter 5: Manifestations of the Buildup of Screening Pigments in the Optical Properties of Plants;103 8.1;5.1 The Factors Affecting In Planta Spectra of Screening Pigments and Radiation Screening Efficiency;104 8.2;5.2 Contribution of Secondary Carotenoids to Absorption of Light by Microalgae;105 8.3;5.3 Stress-Induced Changes in Optical Properties of Cell Structures Containing Screening Pigments;109 8.3.1;5.3.1 Anthocyanin-Containing Vacuoles;109 8.3.2;5.3.2 Carotenoid-Accumulating Plastids;110 8.4;5.4 Selective Screening of PAR and UV Radiation by Cuticle and Epidermis;112 8.5;5.5 The Influence of Screening Pigment Accumulation on Whole-Plant Optical Spectra;116 8.5.1;5.5.1 Manifestations of the Buildup of Flavonols in Reflectance Spectra;117 8.5.2;5.5.2 Effect of Anthocyanins on Leaf and Fruit Spectra;123 8.5.3;5.5.3 Effect of Red Carotenoids on Leaf Reflectance;125 8.6;5.6 Concluding Remarks;127 8.7;References;128 9;Chapter 6: Quantification of Screening Pigments and Their Efficiency In Situ;133 9.1;6.1 Optical Reflectance-Based Techniques for Nondestructive Screening Pigment Assessment;133 9.1.1;6.1.1 The General Approach;134 9.1.2;6.1.2 Anthocyanins;140 9.1.3;6.1.3 Flavonols;142 9.1.4;6.1.4 Carotenoids;144 9.2;6.2 Approaches to Estimation of the Photoprotective Pigment Efficiency In Planta;145 9.3;6.3 Concluding Remarks;152 9.4;References;153 10;Chapter 7: Buildup of Screening Pigments and Resistance of Plants to Photodamage;157 10.1;7.1 Accumulation of Mycosporine-Like Amino Acids and Scytonemin Increases UV Resistance of Photoautotrophs;158 10.2;7.2 Buildup of UV-Absorbing Phenolics and UV Resistance of Plants;159 10.3;7.3 Anthocyanins and Other Phenolics as a Shield Against Excessive PAR;163 10.3.1;7.3.1 Are Anthocyanins Involved in UV Protection?;165 10.3.2;7.3.2 Anthocyanin and Cross-Resistance to Stress;166 10.3.3;7.3.3 Anthocyanins Prevent Photoinhibition and Photobleaching;167 10.4;7.4 Carotenoid Screening Pigments Protect Against Photodamage;169 10.5;7.5 Concluding Remarks;172 10.6;References;173 11;Index;179