The effects of 2,4-D on growth and mitosis in suspension cultures of Daucus carota

Abstract

The mean generation time of suspension cultures of Daucus carota was linearly related to 2,4-dichlorophenoxyacetic acid (2,4-D) concentration over the range 0.1–20 μg ml −1. Cell cycle analysis indicated that suppression of growth by 2,4-D was due to an extension of, or blockage in the G1 or G2 stages of the cell cycle and was associated with lignin deposition at concentrations above 15 μg ml −1. At 2,4-D concentrations from 0.1–30 μg ml −1, mitotic duration increased progressively and mitotic stage proportions were altered such that the durations of prophase and metaphase were increased relative to those of anaphase and telophase. This suggested that 2,4-D was lengthening the period during which the mitotic spindle was assembled and might prevent spindle formation at concentrations greater than 30 μg ml −1.