Life Sciences Commons^™

Growth Analysis Of Tall Fescue Genotypes Differing In Yield And Leaf Photosynthesis, Wallace Wilhelm, C. J. Nelson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Relationships between leaf photosynthesis and yield have not been well defined in forage grasses. Therefore, leaf growth, dry matter distribution, carbohydrate concentration, and growth analysis of four genotypes of tall fescue (Festuca mundinacea Schreb.) were examined. Genotypes, selected in the field for high and low CO₂ exchange rate (CER) in combination with high and low yield, were compared in an attempt to study the relationship between photosynthesis and yield.

In the vegetative growth stage, high yielding genotypes produced greater amounts of all plant parts (leaves, stem bases, and roots) than did low yielding genotypes; however, low yielding genotypes …

Leaf Growth, Leaf Aging, And Photosynthetic Rate Of Tall Fescue Genotypes, Wallace Wilhelm, C. J. Nelson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Leaf growth and leaf aging both influence the total amount of CO, fixed by a particular leaf in the canopy during its photosynthetically productive life. Four genotypes of tall fescue (Festuca arundinacea Schreb.) were selected for all combinations of high and low COB exchange rates (CER) and yield. The purpose of this study was to determine CER during aging and leaf growth rates of tall fescue genotypes in growth chambers and in the field on a Mexico silt loam (Udollic Ochraqualfs; fine, montmarillonitic, mesic). Leaf growth of vegetative tillers in controlled environments was continuous throughout the day for all …

Irradiance Response Of Tall Fescue Genotypes With Contrasting Levels Of Photosynthesis And Yield, Wallace Wilhelm, C. J. Nelson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The purpose of this study was to determine if genotype by irradiance interactions or genetic variation in diurnal trends of CO, exchange rate (CER) influenced the CER-yield relationship in tall fescue (Festuca mundinucea Schreb.). Genotypes were selected in the field for high CER-high yield, high CER-low yield, low CER-high yield, and low CER-low yield. Responses of CER to photosynthetic photon flux density (PPFD) of these genotypes were determined using both growth chamber- and field-grown material. The shapes of the PPFD response curves were similar for all genotypes, and saturation occurred at approximately 1,200 μE m^-2 sec^-1 (400 …

Testicular Steroid Secretion In Response To Gnrh-Mediated Lh And Fsh Release In Bulls, B. D. Schanbacher, S. E. Echternkamp

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Assay of frequently collected blood samples in four mature Hereford bulls indicated the existence of a tonic mechanism for the secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH), i.e., their episodic release was not observed. Increased plasma concentrations of LH and FSH, however, were obtained in response to an intravenous injection of 500 µg of gonadotropin releasing hormone (GnRH). These gonadotropins showed similar secretory profiles after GnRH, but the relative magnitude of the LH response (30-fold) was considerably greater than that of the FSH response (sevenfold).

Concentrations of testosterone in jugular and spermatic vein blood were increased sevenfold …

The Welfare Effects Of Erosion Controls, Banning Pesticides, And Limiting Fertilizer Application In The Corn Belt: Comment, Clayton Ogg

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The recent Journal work by C. Robert Taylor and Klaus Frohberg was an impressive study from the standpoint of both the energy and imagination that must have gone into the model and the practical implications concerning the welfare effects of nonpoint pollution abatement. Yet, it appears that costs of nutrient management were considerably overestimated in the light of a number of experiments using techniques for controlling nutrient losses through proper timing of nitrogen fertilizer applications. Therefore. the model may have failed to represent the most cost effective techniques for reducing nitrogen pollution.