EFFECTS OF HERBICIDES OF DIFFERENT MODES OF ACTION ON LEAF-CELL MEMBRANE PERMEABILITY IN PHASEOLUS VULGARIS

Abstract

Leakage of electrolytes from leaf discs of treated Phaseolus vulgaris L. plants was used to study the effects of several herbicides of different modes of action on leaf-cell membrane permeability. Linuron (N-(3,4-dichlorophenyl)-N-methoxy-N-methylurea), prometryne (4,6-bisisopropylamino-2-methylthio-1,3,5-triazine), bromacil (5,bromo-6-methyl-3-(1-methyl-n-propyl) uracil), sodium azide and dalapon (2,2-dichloropropionic acid) increased leaf-cell permeability at 24 h after treatment and this occurred without appearance of leaf necrosis. Glyphosate (N-(phosphonomethyl) glycine) increased leaf-cell permeability at 96 h and this was always associated with visible injury, including wilting. Paraquat (1,1-dimethyl-4,4-bipyridylium) at 10−5M increased leaf-cell permeability 48 h after treatment, without apparent leaf damage, but at higher concentrations, increased permeability was always associated with visible effects. Chlorpropham (isopropyl N-(d)3-chlorophenyl) carbamate), picloram (4-amino-3,5,6-trichloropicolinic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) did not alter cell permeability even though epinastic symptoms in leaves became evident 24 h after treatment with picloram and 2,4-D.