Abstract

The nucleotide ratio of several RNA species from cotyledons of Pharbitis nil subjected to a single 16 hr night with or without a 15 min light-break, or to continuous light was investigated. RNA species examined were RNAs from nuclear, mitochondrial, microsomal, and supernatant fractions separated by differential centrifugation, and s-, r-, and m-RNAs fractionated by methylated albumin column chromatography.

Of the RNAs examined, m-RNA alone was found to change its nucleotide ratio with photoperiod applied. Thus as compared with m-RNA from non-induced cotyledons (exposed to continuous light or an interrupted night), m-RNA from cotyledons induced by an uninterrupted night contained significantly reduced guanylic and cytidylic acids on molar ratio basis.

A working hypothesis was proposed that floral stimulus production in cotyledons may be directed by gene DNA derepressed photoperiodically.

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