The Reversal of Scotoactive Stomatal Behavior in some Woody Weeds by Paraquat and 2,4,5-T

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Abstract
A typical scotoactive stomatal behavior was noticed inCarissa spinarumL.;Gymnosporia emarginataLaws;Maba buxifoliaCl.;Flacourtia sepiariaRoxb.;Dodonaea viscosaL. andRandia malabaricaLamk. This stomatal behavior was reversed artificially by foliar application of paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) at 100 ppmw or 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] at 2000 ppmw. The size of the stomatal aperture, stomatal conductance and the rates of transpiration were enhanced significantly by the herbicide treatment. The physiological basis for the induction of desiccation and death of plant organs is thought to be the excessive stimulation of stomatal aperture, stomatal conductance and consequently high rates of transpiration observed here. The data suggest that herbicide-induced desiccation is the consequence of inhibition of scotoactive behavior and increased water loss with attendant desiccation and death of leaves.