Although culturing explants on solidified media containing oryzalin increased the 4x:2x ratio, this method was less effective compared to aqueous treatments. For example, none of the solidified media oryzalin treatments resulted in a 4x:2x ratio greater than 0.2 (data not shown) while all of the aqueous oryzalin treatments of 6 h duration or longer exceeded this ratio (Fig. 3).