Studies of herbicide toxicity and mode of action using isolated mesophyll cells and callus-derived cell suspensions

Abstract

Enzymatically isolated mesophyll cells of peanut (Archis hypogeae L.) and callus-derived cell suspensions of peanut and soybean (Glycine max (L.) Merrill) were assessed for their usefulness in studies of the toxicity and (or) mode of action of two bipyridilium herbicides (diquat and paraquat) and of perfluidone. Isolated mesophyll cells were very useful for rapid analyses of photosynthetic inhibition by 1 or 10 μM concentrations of the bipyridiliums. Cells treated with perfluidone were not affected. The growth of nonphotosynthetic callus-derived peanut cell suspensions was inhibited strongly either in the light or in the dark at 1 and 10 μM concentrations of either bipyridilium compound. Growth was slowed in cells treated with 0.1 μM diquat but not paraquat. In contrast, callus-derived soybean cell suspensions grew well in 1 μM diquat or paraquat; 10 μM of either herbicide strongly inhibited growth.Ultrastructural analyses of isolated mesophyll cells were of limited usefulness in assessing herbicide toxicity and mode of action because both untreated and treated enzymatically isolated peanut mesophyll cells had damaged membranes with extensive lipid deposits. In contrast, callus-derived soybean cell suspensions of both treated and untreated cells were undamaged for up to 6 days so that reduced growth of the cultures was not caused by destruction of organelles.