Distribution and exudation of allelochemicals in wheat Triticum aestivum

Wheat allelopathy has potential for weed suppression. Allelochemicals were identified in wheat seedlings, and they were exuded from seedlings into aga r growth medium, p-Hydroxybenzoic, trrms-p-coumaric, cis-p-coumaric, syring ic, vanillic, trans-ferulic, and cis-ferulic acids and 2,4-dihydroxy-7-meth oxy-1,4-benzoxazin-3-one (DIMBOA) were identified in both the shoots and ro ots of 17-day-old wheat seedlings and their associated agar growth medium. Wheat accessions with previously identified allelopathic activity tended to contain higher levels of allelochemicals than poorly allelopathic ones. Th e allelopathic compounds present in the shoots generally also were identifi ed in the roots and in the agar medium. Allelochemicals were distributed di fferentially in wheat, with roots normally containing higher levels of alle lochemicals than the shoots. When the eight allelochemicals were grouped in to benzoic acid and cinnamic acid derivatives, DIMBOA, total coumaric, and total ferulic acids, the amount of each group of allelochemicals was correl ated between the roots and the shoots. Most of the allelochemicals identifi ed in the shoots and roots could be exuded by the living roots of wheat see dling into the agar growth medium. However, the amounts of allelochemicals in the agar growth medium were not proportional to those in the roots. Resu lts suggest that wheat plants may retain allelochemicals once synthesized. The presence of allelochemicals in the agar growth medium demonstrated that wheat seedlings were able to synthesize and to exude phytotoxic compounds through their root system that could inhibit the root growth of annual ryeg rass.