GLYPHOSATE HERBICIDE CAUSES HORMESIS IN WHEAT.

The hormetic response of the most frequently used herbicide, glyphosate can be used to enhance crop growth and yield. A pot study was conducted twice to assess the effect of glyphosate on wheat at different doses (0, 1.8, 3.6, 7.2, 18, 36, 72, 180, 360 and 720 g a.e. ha^-1) sprayed at its 3-4 leaf stage. Observations recorded three weeks after spray and maturity to determine whether growth enhancement was sustained over time. Results revealed that glyphosate application enhanced wheat growth at low doses (up to 36 g a.e. ha^-1) which was sustained over time; conversely, higher doses caused phytotoxicity. Three weeks after spray, the highest plant height and shoot dry weight of wheat was observed at glyphosate dose of 18 g a.e. ha^-1 when compared with the control. While, maximum number of tillers was observed at 36 and 180 g a.e. ha^-1. At maturity, a similar trend was observed on plant height, shoot dry weight and number of tillers. Glyphosate at the rate of 3.6 g a.e. ha^-1 produced higher number of grains; while highest spike length, 1000-grain weight and grain weight plant-1 was observed with 18 g a.e. ha^-1. It was concluded that application of ultralow doses of glyphosate up to 36 g a.e. ha^-1 to wheat at 3-4 leaf stage can stimulate growth. [ABSTRACT FROM AUTHOR]