The comparative cell cycle and metabolic effects of chemical treatments on root tip meristems. II. Propham, chlorpropham, and 2,4-dinitrophenol.

Abstract

The effects of three chemicals, propham (Isopropyl carbanilate), chlorpropham (Isopropyl m-chloro-carbanilate), and DNP (2, 4-dinitrophenol) on oxygen uptake, ATP synthesis, cell division and cell cycle distribution in root tips of pea (Pisum sativum L.) ‘Alaska’ are reported. At the lowest concentration tested for each chemical (chlorpropham, 4.1×10-7 M; DNP, 1×10-6 M; and propham, 1.2×10-6 M) a reduction in the number of cells able to enter into mitosis was observed. DNP and propham induced a small number of abnormal mitoses, but chlorpropham caused a significant percentage of aberrancies (50%). At the higher range of concentrations tested, chlorpropham (4.1×10-4M) induced a similar mitotic inhibition response, but DNP and propham showed differences. Propham (1.2×10-3 M) caused a rapid decrease in number of mitoses so that by 6 hrs less than 1% of the total cells were dividing and all of them were abnormal, by 24 hrs this level was reduced to about 0.2%. DNP (1×10-3 M) caused an initial reduction in the number of mitotic figures followed by severe inhibition of entry into mitosis; division figures were abnormal from 3 hrs onward. DNP at 1×10-3 M caused the complete inhibition of oxygen uptake and ATP synthesis and inhibited mitotic entry and exit after 3 hrs. This study shows that although DNP (an uncoupler of respiration) and propham (a protein synthesis inhibitor) have different modes of action, both have severe and rapid mitotic inhibitory effects. It also reiterates with mitotic kinetic evidence that chlorpropham is a direct mitotic poison.