Effect of different conditions of light on the nucleic acid fractions in cotyledons ofChenopodium rubrutn L.

The nucleic acid fractions in cotyledons of young Chenopodium rubrum plants exposed to continuous light, continuous darkness and short (8 h) day, respectively and labelled with³²P 24 h prior to harvesting were studied by means of chromatography on MAK columns. Some parameters of cotyledon growth (dry weight, cotyledon area, occurrence of mitoses) were also investigated. The changes in the nucleic acid fractions agreed with the dynamics of cotyledon growth. In continuous light the content of all fractions increased. The radioactivity of DNA and s-RNA did not undergo any great changes and only r-RNA increased. The specific activity of r-RNA increased slightly, that of soluble RNA and DNA was reduced. In continuous darkness the content of all the fractions did not undergo any great changes. The radioactivity as well as the specific activity of all fractions decreased. In short day the content of the nucleic acid fractions did not change conspicuously. Only the specific activity of s-RNA increased in a noticeable way while the radioactivity of r-RNA and the specific activity of DNA decreased and this of r-RNA did not change. The changes in nucleic acid metabolism were partially connected with changes in³²P uptake which depended upon light conditions but they were not merely a consequence of this fact. Obviously, there also exists a more direct relationship between nucleic acid synthesis and growth.