Effect of trifluoperazine and verapamil on herbicide stimulated growth of cotton

Pretreatment of hydroponically-grown cotton with trifluoperazine (TFP) and verapamil (VPL), respectively, inhibited 2,4-dichlorophenoxyacetic acid (2,4-D) and metribuzin [4-amino-6-tert-butyl-3-methylthiol,2,4-triazin-5(4H)-one (MTZ)]-induced hermetic growth as measured by total leaf areas and dry weights. Trifluoperazine, an anti-calmodulin drug, proved to be a more effective inhibitor of hermetic growth than VPL, a calcium (Ca2+)-channel antagonist. It is suggested that Ca2+ influx is involved in the growth increase observed in hormesis.