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 s olution into hollow-stemmed crops, may be useful for various studies o f nutrient allocation within the plant. The objectives of this study w ere to assess whether peduncle perfusion was suitable for in vivo stud ies of N and/or C distribution in cereal crops and to determine how N, growth regulator, or sucrose solutions altered C and N accumulation a nd partitioning in barley (Hordeum vulgare L.) and wheat (Triticum aes tivum L. emend. Thell.). Ten treatments [25 and 50 mM N, 30 mu M chlor mequat (2-chloroethyl-N,N,N-trimethyl ammonium chloride), 15 mu M ethe phon [(2-chloroethyl)phosphonic acid], N + chlormequat or ethephon, de tillering + N, 250 mM sucrose, distilled water and non-perfusion] were evaluated in four greenhouse experiments (two for barley, two for whe at). Treatments containing N were enriched with a 5% atom N-15. Perfus ion lasted 30 d beginning 5 to 8 d after spike emergence. The total vo lume of solution taken up ranged from 10 to 178 mL for barley, and 8 t o 129 mL for wheat. The N-15 tracer showed that peduncle-perfused N wa s transported and incorporated into all plant tissues. Applying N incr eased 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), res pectively. 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 gra in or non-grain tissues. The data indicate that peduncle perfusion del ivers substances in solution into both barley and wheat plants. Nitrog en supplied after spike emergence can substantially increase grain N a ccumulation without restricting C deposition.