Shoot Zone Activity of Trifluralin and Nitralin

Abstract

When localized treatments of α,α,α-trifluoro-2,6-di-nitro-N,N-dipropyl-p-toluidine (trifluralin) and 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) were applied to the shoot zone of sorghum (Sorghum bicolor(L.) Moench, var. RS-610) and cucumber (Cucumis sativusL., var. Wis. SMR-15) before seedling emergence, the most susceptible sites were the sorghum coleoptilar node and the cucumber hypocotyl hook. The longer before emergence that the sorghum shoot was exposed to the herbicides, the greater was the injury. However, if herbicide concentration was sufficient, the growing point just above the sorghum coleoptilar node was inhibited by both herbicides when applied after seedling emergence. Maximum uptake of 14C-trifluralin and14C-nitralin occurred through the coleoptilar node and hypocotyI hook of sorghum and cucumber, respectively. Rate of entry, uptake, and translocation of 14C-trifluralin was greater than that of14C-nitralin in sorghum and cucumber shoots.