EVALUATION OF PEDUNCLE PERFUSION FOR IN-VIVO STUDIES OF CARBON AND NITROGEN DISTRIBUTION IN CEREAL CROPS

Peduncle perfusion, a recently developed technique for delivery of N solution into hollow-stemmed crops, may be useful for various studies of nutrient allocation within the plant. The objectives of this study were to assess whether peduncle perfusion was suitable for in vivo studies of N and/or C distribution in cereal crops and to determine how N, growth regulator, or sucrose solutions altered C and N accumulation and partitioning in barley (Hordeum vulgare L.) and wheat (Triticum aestivum L. emend. Thell.). Ten treatments [25 and 50 mM N, 30 mu M chlormequat (2-chloroethyl-N,N,N-trimethyl ammonium chloride), 15 mu M ethephon [(2-chloroethyl)phosphonic acid], N + chlormequat or ethephon, detillering + N, 250 mM sucrose, distilled water and non-perfusion] were evaluated in four greenhouse experiments (two for barley, two for wheat). Treatments containing N were enriched with a 5% atom N-15. Perfusion lasted 30 d beginning 5 to 8 d after spike emergence. The total volume of solution taken up ranged from 10 to 178 mL for barley, and 8 to 129 mL for wheat. The N-15 tracer showed that peduncle-perfused N was transported and incorporated into all plant tissues. Applying N increased grain N concentration an average of 9.5 g kg(-1) for barley and 18.1 g kg(-1) for wheat with levels as high as 36 and 55 g kg(-1), respectively. Nitrogen levels in flag leaves and non-grain tissues of the spike were two- to eight-fold higher in N perfused plants. Perfusion with sucrose or growth regulators did not affect C or N content in grain or non-grain tissues. The data indicate that peduncle perfusion delivers substances in solution into both barley and wheat plants. Nitrogen supplied after spike emergence can substantially increase grain N accumulation without restricting C deposition.