Quinclorac-induced Electrolyte Leakage in Seedling Grasses

Abstract

The mode of action of quinclorac was investigated in broadleaf and grass species. Quinclorac induced characteristic auxinlike symptoms in broadleaf species but not in susceptible grasses. In susceptible grasses, quinclorac caused necrotic bands near the zones of elongation in shoots and roots. Electrolyte leakage was induced by quinclorac in smooth crabgrass and other susceptible grasses but not in tolerant grass or susceptible broadleaf species. In smooth crabgrass, increased electrolyte leakage and reduced fresh weight were rate dependent, and initially specific to young tissues. An inhibitory effect on elongation in the youngest leaf of smooth crabgrass and in primary roots of corn was detected 6 and 3 h after quinclorac treatment, respectively. Electrolyte leakage required more than 12 and 6 h in the leaf and root, respectively. Depolarization of corn root cell membrane potential was not observed in a 6-h treatment period. Results presented here provide additional evidence that quinclorac activity differs between susceptible broadleaf and grass species. In addition, the action of quinclorac appears to be similar in both shoot and root tissues of susceptible grasses. It is proposed that quinclorac-induced electrolyte leakage in susceptible grasses is a secondary response and that the primary mechanism of action involves inhibition of an as yet unknown metabolic process associated with cell expansion.