CHLOROPHYLL AND CHLOROPHYLL DEVELOPMENT 1103 



of carotene are now known; they are unsaturated hydrocarbons of the 

 formula C4oH564f 



The name xanthophyll was given by Berzelius (3a) to the yellow pig- 

 ment from leaves. It is a hydroxyl-containing carotinoid of the formula 

 C40H66O2. Two recent suggestions for the nomenclature of the oxygen- 

 containing yellow pigments are the following: 



Kuhn (35) uses the term xanthophyll as a group name for the hydroxyl- 

 containing carotinoids of the C40 series. Kuhn in agreement with Will- 

 statter has changed the name of the leaf xanthophyll (C40H56O2) to 

 lutein. Von Euler uses the term lutein for the natural mixture of 

 pigments in egg yolk. 



Karrer (30) suggests that the name xanthophyll be reserved for the 

 carotinoid C40H56O2 from the green leaf (= Kuhn's "lutein") and 

 that the oxygen-containing carotinoids with 40 carbon atoms be called 

 phytoxanthins. The names of the individual substances are then to be 

 formed in connection with the place of formation of these substances, 

 e.g., xanthophyll from the green leaf, zeaxanthin from Zea Mays, viola- 

 xanthin, taraxanthin, and fucoxanthin. 



Von Euler and Hellstrom (16a) germinated barley grains in the dark 

 and then exposed them to light. During illumination the increase in 

 carotene and in chlorophyll content go closely parallel and at a higher 

 rate than xanthophyll. In etiolated plants practically no carotene was 

 found. Chlorophyll and carotene formation are apparently photo- 

 chemical reactions. Sjoburg (69) studied the formation of chlorophyll 

 and the yellow plant pigments under varying conditions and at different 

 stages of the development of the plants. The formation of carotinoids 

 and anthocyanins in the blossoms was the same in light and darkness. 

 Guthrie (24) studied the effect of environmental conditions on chloroplast 

 pigments. Some of his results may be noted : (a) Increasing the duration 

 of illumination results in a decrease in total chlorophyll and carotinoids 

 as measured on the dry-weight basis. (6) Screening out the ultra-violet 

 light from sunlight has no significant effect on chlorophyll or carotinoids. 

 (c) Screening out the red light results in an increase in both chlorophyll 

 and carotinoids, but this is partially due to intensity reduction. The 

 ratio chlorophyll a : chlorophyll h is higher under blue light, but the num- 

 ber of analyses was insufficient to be certain of this increase. Brown 

 pigment production is favored by blue light, (d) Reducing the light 

 intensity to 12 per cent of normal sunlight results in an increase in 

 chlorophyll and carotinoids. The chlorophyll a: chlorophyll b and 

 carotene : xanthophyll ratios show no significant change. Brown pig- 

 ment is reduced, (e) Placing plants in the dark results in a large decrease 

 in chlorophyll unaccompanied by a corresponding decrease in carotinoids. 

 The carotene : xanthophyll ratio shows a marked increase. Brown pig- 

 ment increases. 



