The role of coleoptile on barban sensitivity between wild oat and wheat

Differential sensitivity of wild oat (Avena fatua L.) and wheat (Triticum aestivum L.) to barban (4-chloro-2-butynyl-m-chlorocarbanilate) was highest when barban was applied to the coleoptile. The coleoptile acts as a physical and physiological barrier to reduce the concentration of free barban in the stem section where the sensitive meristematic sites are located. Metabolism of barban was higher ïn the coleoptile of tolerant wheat than in that of susceptible wild oat. Free barban concentration was higher in the stem of wild oat than in the stem of wheat after 24 hr, but after 48 hr, concentrations were similar. The coleoptile appears to enhance the differential sensitivity to barban between wild oat and wheat.