Source and Magnitude of Ammonium Generation in Maize Roots1

Studies with 15N indicate that appreciable generation of NH4+ from endogenous sources accompanies the uptake and assimilation of exogenous NH4+ by roots. To identify the source of NH4+ generation, maize (Zea mays L.) seedlings were grown on 14NH4+ and then exposed for 3 d to highly labeled 15NH4+. More of the entering 15NH4+ was incorporated into the protein-N fraction of roots in darkness (approximately 25%) than in the light (approximately 14%). Although the 14NH4+ content of roots declined rapidly to less than 1 μmol per plant, efflux of 14NH4+ continued throughout the 3-d period at an average daily rate of 14 μmol per plant. As a consequence, cumulative 14NH4+ efflux during the 3-d period accounted for 25% of the total 14N initially present in the root. Although soluble organic 14N in roots declined during the 3-d period, insoluble 14N remained relatively constant. In shoots both soluble organic 14N and 14NH4+ declined, but a comparable increase in insoluble 14N was noted. Thus, total 14N in shoots remained constant, reflecting little or no net redistribution of 14N between shoots and roots. Collectively, these observations reveal that catabolism of soluble organic N, not protein N, is the primary source of endogenous NH4+ generation in maize roots.

Proglacial river dataset from the Akuliarusiarsuup Kuua River northern tributary, Southwest Greenland, 2008 - 2010, version 1.0

Pressing scientific questions concerning the Greenland ice sheet's climatic sensitivity, hydrology, and contributions to current and future sea level rise require hydrological datasets to resolve. While direct observations of ice sheet meltwater losses can be obtained in terrestrial rivers draining the ice sheet and from lake levels, few such datasets exist. We present a new dataset of meltwater river discharge for the vicinity of Kangerlussuaq, Southwest Greenland. The dataset contains measurements of river stage and discharge for three sites along the Akuliarusiarsuup Kuua (Watson) River's northern tributary, with 30 minute temporal resolution between June 2008 and August 2010. Additional data of water temperature, air pressure, and lake water depth and temperature are also provided. Discharge data were measured at sites with near-ideal properties for such data collection. Regardless, high water bedload and turbulent flow introduce considerable uncertainty. These were constrained and quantified using statistical techniques, thereby providing a high quality dataset from this important site. The greatest data uncertainties are associated with streambed elevation change and measurements. Large portions of stream channels deepened according to statistical tests, but poor precision of streambed depth measurements also added uncertainty. Quality checked data are freely available for scientific use as supplementary online material.

UM Men's Swimming Team, 1987

Front Row: swimming coach Jon Urbanchek, Stephen Hamerski, William T. Hayes, Michael G. Bayerl, David A. Kerska, co-captain Joseph E. Parker, Lee C. Michaud, Mats O. Nygren, diving coach Dick Kimball.

2nd Row: manager Jeff Gordon, Martin T. Moran, Richard K. Wilkening, Richard R. Fabian, Matthew R. Smith, Caldwell B. Esselstyn, Matthew D. Curry, Daniel J. Dewhirst, Guy R. Williams.

3rd Row: Timothy S. Petsche, Jon A. Teppo, Jim A. O'Donnell, Alejandro Alvizuri, Ronald M. Melnyk, Alec Campbell, Mike Creaser, David R. McNear, Gregory B. Varner, grad assistant Marc C. Parrish.

4th Row: assistant coach Fernando Canales, Bjoern Warland, Christopher J. Martin, Jan-Erick Olsen, David Goch, William J. Kopas, Robert M. Ceresa, Brent D. Lang, grad assistant Alex Wallingford.

Education for a new Colombia /

"OE-14152"

Surfactant effects on pesticide photochemistry in water and soil /

Grant no. R-802959.

The way of honor /

Mode of access: Internet.

Radioisotopes in medicine /

Prepared for: Office of Isotopes Development, United States Atomic Energy Commission.

The eternal search; the story of man and his drugs.

Mode of access: Internet.

Calibration and testing of selected portable flowmeters for use on large irrigation systems /

"September 1980."--P. 2 of cover.

Evaluating methods for determining water use in the High Plains in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming, 1979 /

Bibliography: p. 30.

Young men and drugs in Manhattan : a causal analysis /

Mode of access: Internet.

K-8 proposed Lakewood School plan for career education : school district #4 Twin Lakes, Twin Lakes, Wisconsin 53181 /

WI docs. no.: Ed.3/2:8352

Estimating 1980 ground-water pumpage for irrigation on the high plains in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming /

Bibliography: p. 35-36.

The anatomy of the fetal pig,

Includes index.