XXXV 

 RADIATION AND ANTHOCYANIN PIGMENTS 



John M. Arthur 



Boyce Thompson Institute for Plant Research 



Introduction. Light and anthocyanin pigtttents. Carbohydrate accumulation and 

 anthocyanin development. Relation of anthocyanin production to environment. Tem- 

 perature, radiation, and anthocyanin formation. Absorption and transmission of 

 anthocyanin pigments. Canclusion. References. 



INTRODUCTION 



The eye of man was attracted, probably from the beginning, by the 

 bright pigments of plant leaves, flowers, and fruit. The first studies of 

 these pigments, therefore, date back to the first studies on the physiology 

 of plants. In 1664, Robert Boyle (8) recorded his observations that 

 syrup of violets turned red when vinegar or any other acid liquor was 

 added. Since that time the bibliography on this subject has accumulated 

 at a rapid rate. Onslow (25) has published a book on the anthocyanin 

 pigments which gives 879 references to publications on this single group 

 up to the year 1925 and this is by no means complete. Mobius (25), 

 in 1927, published a monograph on various kinds of plant pigments. 

 This publication includes more than 300 references. In general, the 

 possibility of formation of pigments is largely determined by hereditary 

 factors. The degree of pigmentation may be, and often is, determined 

 by environmental factors. For a discussion of factors other than light 

 which affect pigment formation, the reader should consult the book by 

 Onslow mentioned above. 



The effect of light and darkness on some of the red and blue antho- 

 cyanin pigments was ob-served in 1799 by Senebier (32). Crocus and 

 tulip flowers he found developed pigment in the dark. Sachs (28) 

 confirmed the work of Senebier and added iris and hyacinth to the list 

 of flowers developing pigment in the dark. Sachs also found another 

 group of flowers which developed color only if the buds were exposed to 

 light until the time of opening. Brassica, Tropaeolum, Papaver, and 

 Cucurhita were included in this list. Where shoots only of these plants 

 were darkened, the flowers which developed upon these had a less brilliant 

 coloration. Sorby (33) studied the absorption bands of extracted pig- 

 ments as well as the development of colors in the plants. He observed 

 that the production of red pigment in leaves often depended upon 

 light, since a leaf, when partially covered by an opaque screen, such as 

 another leaf, did not develop pigment under that screen. Sorby was 



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