Abstract
IPC (O-isopropyl N-phenyl carbamate), CIPC (isopropyl N-(3-chlorophenyl) carbamate), and barban (4-chloro-2-butynyl N-(3-chlorophenyl) carbamate) are selective herbicides which inhibit growth of young seedling plants without causing immediate death. We find these compounds useful in making determinations of plant chromosome number and studies of their morphology in root tips. Treatment is with aqueous solutions ranging from 2.5 to 80 ppm for periods of 0.5 to 6 hours, followed by staining by the aceto-orcein squash method. IPC and CIPC cause mitotic activity to cease almost immediately. Chromosomes undergoing mitosis contract, in all species of plants studied, including some that have been reported to show no response to colchicine, 8-hydroxyquinoline, para-dichlorobenzene, and other chemicals used for this purpose. Metabolic nuclei show changes, also, suggesting that the herbicidal action of these compounds may be due to inhibition of messenger RNA synthesis by the DNA template. Uniformly good results to date on many species of plants suggest that IPC and CIPC may well replace chemicals now commonly used for facilitating cytological studies of plant cells. They are decidedly less hazardous to health than colchicine, and considerably cheaper to use.
