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We examined three different-ploidy wheat species to elucidate the development of aboveground architecture and its domesticated mechanism under environment-controlled field conditions. Architecture parameters including leaf, stem, spike and canopy morphology were measured together with biomass allocation, leaf net photosynthetic rate and instantaneous water use efficiency (WUEi). Canopy biomass density was decreased from diploid to tetraploid wheat, but increased to maximum in hexaploid wheat. Population yield in hexaploid wheat was higher than in diploid wheat, but the population fitness and individual competition ability was higher in diploid wheats. Plant architecture was modified from a compact type in diploid wheats to an incompact type in tetraploid wheats, and then to a more compact type of hexaploid wheats. Biomass accumulation, population yield, harvest index and the seed to leaf ratio increased from diploid to tetraploid and hexaploid, associated with heavier specific internode weight and greater canopy biomass density in hexaploid and tetraploid than in diploid wheat. Leaf photosynthetic rate and WUEi were decreased from diploid to tetraploid and increased from tetraploid to hexaploid due to more compact leaf type in hexaploid and diploid than in tetraploid. Grain yield formation and WUEi were closely associated with spatial stance of leaves and stems. We conclude that the ideotype of dryland wheats could be based on spatial reconstruction of leaf type and further exertion of leaf photosynthetic rate.

Corn (Zea mays L.) producers in the rainfed regions sometimes sidedress fertilizer N according to pre-plant-nitrate test (PPNT) results based on the assumption that there is a linear relationship between pre-sidedress nitrate test (PSNT) and the PPNT. There has been no report on such relationship in Ontario (Canada) and elsewhere in the nonirrigated corn-growing regions. A field study was conducted near Ottawa, Canada for 7 y to (1) determine changes in soil available N from pre-planting to shortly after the sidedress stage (late June) for corn and (2) establish a quantitative relationship between PPNT and PSNT. In each year, soil samples from fields of three to four plot experiments with different cropping histories, soil textures, and management levels, taken at 7 to 10 d intervals, and from on-farm trials taken at pre-planting and pre-sidedress, were extracted with 2 M KCl. The concentrations of NO À 3 -N were determined colorimetrically. It was found that soil NO À 3 -N concentration of PSNT was a linear function of PPNT with an average slope of 1.7. However, the slope of the regression equations differed dramatically among cropping sequences, and to a lesser extent, soil textures. The NO À 3 -N concentration after planting to pre-sidedress was influenced by air temperature and precipitation during this period of time. Both PPNT and PSNT positively correlated with corn-grain yield. Our data suggest that cautions must be taken when deciding the rate of fertilizer N for sidedress application to corn based on PPNT test, especially under more humid northern climate conditions.

Although much investigated, the factors constraining cereal grain protein accumulation are not well understood. As a result of the development of a new technique, new approaches to this question are now possible. A peduncle perfusion system was used to deliver a range of plant growth regulators (PGRs) and/or N solutions into barley (Hordeum vulgare) plants during the grain‐filling period. The perfusion technique floods the peduncle interior with a treatment solution for periods of weeks to months, allowing the plant to take up administered substances from the perfused solution. The objectives of the present work were to determine: (1) whether some PGRs could alter the overall pattern of N allocation within barley plants, perhaps leading to higher protein accumulation in the seeds, (2) whether the addition of N through the peduncle could increase the seed N concentration even when the concentration of N in the rooting medium was high, and (3) whether or not PGR‐stimulated elevations in grain protein levels and peduncle‐added N increases in grain protein levels were additive. Three experiments were conducted to determine the physiological effects of (1) peduncle‐administered PGRs (2) combinations of soil‐ and peduncle‐applied N and (3) selected combinations of soil‐ and peduncle‐administered N, and peduncle‐applied PGRs on photosynthetic rate, dry matter partitioning and N accumulation of barley plants during grain filling. The first experiment tested four PGRs: abscisic acid (ABA), kinetin, gibberellic acid (GA3), and 2,4‐dichlorophenoxy acetic acid (2,4‐D) each at three concentrations. The second experiment tested three levels of soil N (NH4NO3) fertility, and two concentrations of peduncle‐added N (urea). The third experiment tested four PGRs: ABA, kinetin, GA3, and 2,4‐D with two soil N concentrations and two concentrations of peduncle‐added N. ABA and 2,4‐D decreased total seed weight of the perfused spike. The addition of peduncle‐perfused N increased seed protein concentration and content under conditions of high soil N fertility, suggesting that seed protein accumulation is more limited by the ability of roots to take up N from the soil than by the seed to take up N from the rest of the plant. The effects of the PGRs on N allocation among plant parts varied with the amount of N available to the plant. Because it resulted in less protein stored in the flag leaf and more in the seeds, GA3 perfusion caused an overall change in the allocation of N among plant parts. Peduncle perfusion of kinetin and ABA affected some aspects of photosynthetic physiology.