Synthesis of DNA and of Hydrolytic Enzymes in Cotyledons of Germinating Seeds of Agrostemma githago L.

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Summary In imbibing seeds of Agrostemma githago DNA is synthesized firstly in the root tips of the embryos even before the radicle protrudes, whereas the incorporation of [ 3 H]-thymidine remains on a low level in the cotyledons. Only after germination a drastic enhancement of [ 3 H]-thymidine incorporation starts also in the cotyledons. This incorporation is due to a nuclear DNA synthesis. In about 70% of the cell nuclei the DNA content is doubled during a germination period of 120 h, i. e. it is raised from 2 C to 4 C, whereas the doubling starts after 24 h which is hardly followed by cell divisions. After beginning of DNA synthesis in the cotyledons the formation of hydrolytic enzymes (acid phosphatase, α -amylase and invertase) turns on as deduced from increasing enzyme activities. Several experiments with specific inhibitors suggest a correlation between DNA synthesis and formation of hydrolytic enzymes. We suggest that DNA synthesis in cotyledons is a prerequisite for the formation of hydrolytic enzymes.