RELATIONSHIP BETWEEN PLASTID MUTAGENESIS INDUCED BY N-NITROSOMETHYLUREA AND AGE OF GERMINATING SUNFLOWER SEEDS AT THE TIME OF TREATMENT

The optimal time range for induction of plastid chlorophyll mutations by N-nitrosomethylurea (NMU) during sunflower seed germination was det ermined. It is shown that treatment of seeds germinating for 0 - 24 h with NMU at concentrations 0.01% and 0.015% induces mutations only in the range of 9 - 18 h of germination with a pronounced maximum at 12 t o 15 h. In three-hour intervals adjacent to this maximum, a substantia l decrease in the efficiency of induction is observed, especially duri ng 15 to 18 h of germination.