An Analytic Study of the w-3 Genetic Lesion in Zea mays L.

'I'lle biosyntlhesis of chloropllyll in the albino w-3 maize seedling,s was found to proceed in the same way as in its normal counter part (1,9). However, the nlewly formed clhlorophyll in the w-3 mitutant seed'inigs (lisappears rapidly in light unider aerobic cotnditionls. For this reasoni Koski (9) conlcluded that there was no genetic lesion in the chlorophyll synithesis of the w-3 miiutant, but the mutanit lost clhlorophyll in the light due to inability to preserve the pigmnent after its formiiation. In addition to the photolability of the w-3 chlorophyll, the mutant was devoid of carotenoids, and accumulated the precursors, l)olyenes, of carotenoids both in light and darkness (1,12,13). Anderson and Robertson (1) suggested that the genetic lesion could be placed in one of the biosynthetic steps of carotenogenesis in w-3 mutant. Carotelnoids in the nornmal green seedlings may then be suggested to play a role as photoprotector of chlorophylls from photo-oxidative destruction. Such a role has been assigned to the carotenoids of a photosynthetic bacterium, Rhlodopseu.doiionoas sphleroides (6,15). For investigation of the possible cytoplasnuic influence upon the development of the chloroplast, the w\7-3 allele was incorporated into a number of Mexican races by the appropriate breeding miiethod. Fromi segregatineg progeniies, w-3 mlutants were selected for anlalysis of their pigmlent conitent. Each w-3 mutant in a differenit racial background was miiade to produce a limited quantity of chlorophyll, and the newly formed chlorophyll was tested for its photosynthetic carbon dioxide assimilation in vivo.