FUNCTION OF CAROTENOIDS IN PHANEROGAMS 



Wynd and Noggle found that, in Kansas, soil with the following 

 characteristics produced crops with high yields of carotene : -base- 

 exchange capacity 20 m.equiv., total replaceable base, 20 m.equiv., 

 replaceable calcium 18 m.equiv., and replaceable magnesium 2 m. 

 equiv., per 100 g. of soil ; loss on ignition 4 per cent., and nitrogen 

 content 0-09 per cent. Less than 15 m.equiv. of replaceable base and 

 0-08 per cent, of nitrogen render the soil unsatisfactory. 



INHERITANCE STUDIES ON CAROTENOIDS 



It was in 1920 that Steenbock and Boutwell^^s showed that maize 

 with white endosperm was deficient in vitamin A activity ; eight years 

 later Hauge and Trost^^* indicated that this activity in maize was 

 transmitted exclusively with the yellow endosperm. In recent years, 

 with the identity of the carotenoids well established and their quantita- 

 tive assay rendered comparatively simple with the use of spectro- 

 photometers, considerable progress has been recorded. Johnson and 

 Miller ^ ^ 7 have confirmed and extended the early work of Mangelsdorf 

 and Fraps. ^^s Using mature grain from 19 inbred lines they revealed 

 a very close relationship between the number of dominant Y genes for 

 yellow endosperm colour and both carotene and total carotenoid con- 

 centration. However, the carotenoid content of leaf tissue from white 

 endosperm lines was slightly higher than that from yellow endorsperm 

 lines ; this strongly suggests that carotenoid formation in the leaf 

 and formation (and/or storage) in the endosperm are independent 

 processes. 



Johnson and Miller ^^a further studied the immediate effects of 

 cross pollination on the carotenoid content of maize endosperms, and 

 found large variations within 35 inbred lines ; they obtained evidence 

 that carotenoid inheritance is subject to the usual xenia effects. These 

 variations within inbred lines have been generally confirmed by 

 Porter, Strong, Brink and Neal, ^ ^ ° by Emsweller, Burrell and 

 Borthwick^^i and by Aurand, Miller, and Huberi3 2^ Porter et al, 

 however, consider that those variations are small compared with sea- 

 sonal maturity factors. Emsweller et al. maintain that interbreeding 

 does increase uniformity to some e?^tent. Porter et al. also noted that 

 when inbred strains are compared on the basis of the time required 

 to reach a certain stage, those plants needing the longest time contained 

 relatively and absolutely more carotenoids than those requiring 

 shorter times. This is not considered to be due to any inherent increase 

 in ability to elaborate carotenoids, but to the longer growing period ; 



79 



