The effect of ethylene on root meristems of Pisum sativum and Zea mays.

Ethylene at a concentration of 100 μl l(-1) causes a slight increase in the duration of the mitotic cycle in the primary root meristems of both Pisum sativum L. and Zea mays L. This is due to a lengthening of the G 1 phase; other phases of the cycle are unaffected. Autoradiography and microdensitometry show that the rate of (3)H-thymidine incorporation into nuclei of Pisum is maximal when about half the DNA has been replicated, and that ethylene has no effect upon this rate. Ethylene causes a reduction of the number of dividing cells in the root meristem, particularly in Pisum.