Plant Biology Commons^™

Introduction From The Changing Prairie: North American Grasslands, Anthony Joern, Kathleen H. Keeler

School of Biological Sciences: Faculty Publications

Preserving remaining North American grasslands requires a multiability approach. In this book, we investigate three aspects of an admittedly larger problem: (1) how we as humans perceive grasslands; (2) the ecology of grasslands, in order to define the framework within which conservation and preservation efforts must operate; and (3) conservation issues. Additional sociological, economic, philosophical, and cultural considerations will provide important additional insights to preserving and managing grasslands, but are not included here. By restricting our focus to only three issues, we feel that we can provide a basic, but appropriate, understanding of grassland ecosystems for the prairie enthusiast. This …

Preface From The Changing Prairie: North American Grasslands, Kathleen H. Keeler, Anthony Joern

School of Biological Sciences: Faculty Publications

North American grasslands have figured prominently in our North American heritage. Prairies first provided significant barriers to westward expansion, and then offered both economic and sociological opportunity, as well as heartache, for settlers. Many artists have gained significant inspiration from the beauty as well as the harshness of this region and its biota. And because of ideal climate and soil conditions, these grasslands have provided the agricultural foundation of which much of the economic growth and stability of the United States has historically depended.

Yet many see North American prairies as beautiful only when manipulated or exploited: Green croplands or …

Population Processes, Kathleen H. Keeler, Anthony Joern

School of Biological Sciences: Faculty Publications

Within the prairies, myriad populations of plants, insects, small mammals, and other organisms form distinct levels of organization. The physical forces of weather and fire and the complex networks of species interactions control each species’s structure and dynamics and determine its abundance or rarity. Variation in population dynamics and interactions over time and space determine the distribution and abundance of species, and ultimately the composition and dynamics of entire prairie communities.

To the casual observer, plant populations on prairies may seem quite static, like museums containing a diverse collection of specimens that can be seen again and again on repeated …

Getting The Lay Of The Land: Introducing North American Native Grasslands, Anthony Joern, Kathleen H. Keeler

School of Biological Sciences: Faculty Publications

The expected catastrophic extinction of species (already under way in many places) will alter the planet’s biological diversity so profoundly that, at the known rate of extinction, it will take millions of years to recover. Yet few ecologists study extinction. Indeed, very little ecology deals with any processes that last more than a few years, involve more than a handful of species, and cover an area of more than a few hectares. The temporal, spatial and organizational scales of most ecological studies are such that one can read entire issues of major journals and see no hint of impending catastrophe. …

Keys And Distributional Maps For Nebraska Cyperaceae, Part 1: Bulbostylis, Cyperus, Dulichium, Eleocharis, Eriophorum, Fimbristylis, Fuirena, Lipocarpha, And Scirpus, Steven B. Rolfsmeier

Transactions of the Nebraska Academy of Sciences and Affiliated Societies

Keys and distributional maps are provided for nine genera and 43 species of Cyperaceae documented from Nebraska (excluding Carex). Two species--Eleocharis elliptica and Fimbristylis vahlii--are newly reported for the state, while seven species attributed to the state in the Flora of the Great Plains (Great Plains Flora Association, 1986)--Eleocharis compressa, E. verrucosa, E. wolfii, E. xyridiformis, Scirpus georgianus, S. smithii, and S. torreyi--are deleted based on re-identifications, lack of specimen evidence, or specimens of doubtful provenance in the state. Notes on local systematic problems within the family are also included.

In Vitro Starch Disappearance Procedure Modifications, C. J. Richards, Jeffrey F. Pedersen, R. A. Britton, R. A. Stock, C. R. Krehbiel

Department of Agronomy and Horticulture: Faculty Publications

Four in vitro experiments evaluated the effects of ruminal fluid inoculum:artificial saliva ratios,

grinder type, grind size, and diet of ruminal fluid donor on in vitro starch disappearance. Experiment 1 examined rates of starch disappearance and coefficients of determination obtained by linear regression of starch disappearance using five grain sorghum (Sorghum bicolur (L.) Moench) lines, a corn (Zeu muys L.) control, and a wheat (Triticum aestivum L.) control. Grains were incubated for 4, 8, 12, 16, and 20 h with inoculum varying in proportion of ruminal fluid and artificial saliva ( l:l, 1:2, 1:3, and 1:4). In …

An Automated Plot Harvest System For Use With A Commercial Forage Harvester, Jeffrey F. Pedersen, Kenneth J. Moore

Department of Agronomy and Horticulture: Faculty Publications

This automated harvest system is based on minimal modification of currently available commercial forage harvesters. Using 6.8 m plots separated by 0.75 m alleys, a single operator can harvest, finely chop, and collect wet plot weights of forage sorghum [Sorghum bicolor (L.) Moench] or pearl millet [Pennisetum glaucum (L.) R. Hr.] in <1 min per plot. Harvested material is deposited in a pile in the center of each plot. Subsamples for moisture and quality analysis can easily and safely be obtained from the pile.

Brown· Midrib Sorghum Silage For Midlactation Dairy Cows, R. J. Grant, S. G. Haddad, K. J. Moore, Jeffrey F. Pedersen

Department of Agronomy and Horticulture: Faculty Publications

Brown midrib sorghum silage was compared with alfalfa, corn, and normal sorghum silages for its effect on performance, ruminal metabolism, and digestive kinetics of Holstein dairy cows in midlactation. Twelve cows averaging 90 ± 5 DIM were assigned to one of four diets in replicated 4 X 4 Latin squares with 4-wk periods. Additionally, 3 ruminally fistulated cows (95 ± 20 DIM) were assigned to the same diets in a 3x 4 Youden square for measurement of ruminal characteristics. Diets were fed as isonitrogenous TMR that contained 65% silage (OM basis). The DMl was greater for the corn and brown …

Proposal For Center For Grassland Studies, Ron Case, Dick Clark, Charles A. Francis, Tony Joern, Terry J. Klopfenstein, Lowell E. Moser, Bob Shearman, Ken Vogel, Steven S. Waller

Center for Grassland Studies: Newsletters

Its my pleasure, on behalf of the Grassland Studies Task Force, to forward a proposal for a Center for Grassland Studies for your consideration. The Task Force is extremely pleased with the overwhelming support from a broad base of input. The Task Force has made a major effort through internal and external listening sessions to insure that there was support and in doing so develop a coalition of partners across the University of Nebraska System, state colleges, community colleges, industry, state and federal agencies, public groups, private non-profit organizations and other educational institutions in the region.

Nebraska has a rich …

Identification And Characterization Of Aspergillus Nidulans Mutants Defective In Cytokinesis, Steven D. Harris, Jennifer L. Morrell, John E. Hamer

Department of Plant Pathology: Faculty Publications

Filamentous fungi undergo cytokinesis by forming crosswalls termed septa. Here, we describe the genetic and physiological controls governing septation in Aspergillus nidulans. Germinating conidia do not form septa until the completion of their third nuclear division. The first septum is invariantly positioned at the basal end of the germ tube. Block-and-release experiments of nuclear division with benomyl or hydroxyurea, and analysis of various nuclear division mutants demonstrated that septum formation is dependent upon the third mitotic division. Block-and-releasee xperiments with cytochalasin A and the localization of actin in germlings by indirect immunofluorescence showed that actin participated in septum formation. In …

Purification Of The Major Soybean Leaf Acid Phosphatase That 1s Increased By Seed-Pod Removal, Paul E. Staswick, Chuck Papa, Jing-Feng Huang, Yoon Rhee

Department of Agronomy and Horticulture: Faculty Publications

Fruit removal for 5 weeks after flowering increased acid phosphatase activity 10-fold in soybean (Glycine max 1. Merr. vai Hobbit) leaves compared with normal seed-pod-bearing plants. The major acid phosphatase activity in leaves was purified over 2700-fold, yielding a single polypeptide of 51 kD with a specific activity of 1353 units/mg protein using p-nitrophenylphosphate as the substrate. lsoelectric focusing demonstrated that the purified protein co-migrated with a majority of the activity that increased in leaves following seed-pod removal. lmmunoblot analysis demonstrated that at least part of the increased activity was dueto an increased abundance of the phosphatase protein. In situ …

Models To Predict Yield Loss Due To Weeds In Rice Ecosystems, John L. Lindquist

Department of Agronomy and Horticulture: Faculty Publications

Yield loss models have been developed and evaluated for irrigated rice ecosystems with respect to effects of Echinochloa crusgalli. Simple regression models that give the relation between yield loss and weed density or relative leaf area are discussed with respect to their practical value in weed management in rice. More complex eco-physiological process models have been developed and used for rice ecosystems as well. Such models can be useful as a tool in research, whereas more simple approaches are needed for practical application in weed management.

Cdna Sequence For The Ribulose 1,5 Bisphosphate Carboxylase/Oxygenase Complex Protein A Protein That Accumulates In Soybean Leaves In Response To Fruit Removal, Paul E. Staswick, Steven J. Crafts-Brandner

Department of Agronomy and Horticulture: Faculty Publications

Soybean (Glycine max L.) transiently accumulates two abundant vegetative storage proteins, VSP A and VSP B, in vacuoles of above-ground vegetative tissues (Wittenbach, 1983; Staswick, 1990). As older leaves and stems become a source of exported metabolites for developing sinks, the VSPs are preferentially degraded and the resulting metabolites are presumably mobilized in the xylem and phloem stream. A striking feature of these proteins is that VSP gene expression is dramatically increased in mature leaves following the remova1 of reproductive sinks (seed pods) and the amount of these proteins increases accordingly (for review, see Staswick, 1994). Other changes …

Effect Of Organic Matter Decomposition Level On Bacterial Species Diversity And Composition In Relationship To Pythium Damping-Off Severity, Michael J. Boehm, L.V. Mdden, H.A.J. Hoitink

Department of Plant Pathology: Faculty Publications

Rhizosphere bacteria were isolated from root tip segments of cucumber seedlings grown in a suppressive, slightly decomposed light-colored peat mix, a conducive, more decomposed dark-colored peat mix, and a suppressive dark peat mix amended with composted hardwood bark. The bacteria were identified by a gas chromatographic fatty acid methyl ester analysis. The total number of taxa recovered from a single root tip segment ranged from 9 to 18. No single taxon predominated on all root tip segments harvested from any of the mixes. The highest relative population density reached by a given taxon on any root tip segment was 45%. …

Molecular Approaches For Control Of Tomato Bushy Stunt Virus, H. B. Scholthof, M. Borja, Thomas Jack Morris, A. O. Jackson

School of Biological Sciences: Faculty Publications

I N this overview strategies are discussed that are currently being tested in our laboratory in an effort to engineer resistance against tomato bushy stunt virus (TBSV) in plants. TBSV is chosen as a model-system since this is an economically important RNA virus that is well characterized at the molecular level and the virus has some interesting and potentially useful features that can be exploited to produce resistant plants. Moreover, we anticipate that the information derived from our studies with TBSV will be applicable in developing resistance to other plant viruses. Some approaches that we are attempting to apply to …

Genetic Manipulation Of Tall Fescue, Jeffrey F. Pedersen, D. A. Sleper

Department of Agronomy and Horticulture: Faculty Publications

Genetic manipulation of tall fescue (Festuca arnndinacea Schreb.) has not been altered by the discovery of the Acremonium coenophialum (Morgan-Jones and Gams) / grass interaction. However, tall fescue breeding programs have been affected greatly. The basic methods for genetically manipulating the grass have remained static. Tall fescue is an obligate out-crossing species, and most improvements are, therefore, captured in the form of an improved population developed through some form of mass or recurrent selection. What has changed is the breeder's ability to recognize genetic differences in the grass because of the confounding effect of A. coenophialum on plant phenotype. It …

Comparison Of Sorghum And Indiangrass Chloroplast Genomes Using Rflps, Jeffrey F. Pedersen, R. D. Lee, D. J. Lee, K. P. Vogel

Department of Agronomy and Horticulture: Faculty Publications

Sorghum (Sorghum bicolor (L.) Moench) and indiangrass (Sorghastrum nutans (L.) Nash) appear closely related based on morphological and chemotaxonomic characters. Each species could potentially provide desirable traits to the other. However, traditional breeding techniques have been unsuccessful in hybridizing these two species. The objective of this study was to determine the relatedness of sorghum and indiangrass chloroplast DNA using RFLPs. Eleven sorghum lines in several cytoplasms, two indiangrass popu1ations, and a corn line were studied using 60 proberestriction enzyme combinations. Principal component analysis of the results showed sorghum to be as closely related to corn as to indiangrass, with no …

Developmental Morphology Of Tropical Sorghum And Sorghum X Sudangrass, R. B. Mitchell, K. J. Moore, Jeffrey F. Pedersen, T. A. Peterson, L. E. Moser, D. D. Redfearn

Department of Agronomy and Horticulture: Faculty Publications

Tropical sorghum and sorghum x sudangrass are known to be efficient scavengers of soil nitrogen and are important forage crops in the U.S. Nitrate contamination of groundwater due to disposal of organic wastes and excessive fertilization is a major concern in the Central Great Plains. A common disposal method of municipal wastes is application to fallow cropland. Quantification of the developmental morphology of tropical sorghum and sorghum x sudangrass is important to developing management strategies that allow multiple applications of organic wastes to optimize nitrogen removal and dry matter production. The objective of this study was to quantify the developmental …

Breeding Systems For Cross-Pollinated Perennial Grasses, K. P. Vogel, Jeffrey F. Pedersen

Department of Agronomy and Horticulture: Faculty Publications

I. Introduction

II. Reproductive and Breeding Characteristics

III. Breeding Systems

A. Ecotype Selection

B. Recurrent, RestricteclPhenotypic Selection

C. Half-sib Progeny Test

D. Between and Within Family Selection

E. Recurrent Multistep Family Selection

IV. Gains From Selection

A. Time Interval per Cycle

B. Potential Gain per Cycle .

C. Potential Inbreeding per Cycle

V. Polycrossing

VI. Hybrid Cultivars

VII. Conclusions

Literature Cited

Local Polyploid Variation In The Native Prairie Grass Andropogon Gerardii, Kathleen H. Keeler

School of Biological Sciences: Faculty Publications

The microscale distribution of polyploid variants of the dominant grass big bluestem (Andropogon gerardii) in virgin tallgrass prairie was mapped using flow cytometry. The correlation between DNA content and polyploidy allows the use of flow cytometry for nondestructive determination of polyploidy in intact plants. At Konza Prairie, local plots contained from 0 to 100% hexaploid cytotypes but most showed fine-scale mixing of the polyploid variants. The relationship of cytotype frequency to moisture availability or burning history was nonsignificant

Jasmonate, Genes, And Fragrant Signals, Paul E. Staswick

Department of Agronomy and Horticulture: Faculty Publications

Although first recognized for its growth-inhibiting activity about 20 years ago, JA² and its fragrant methyl ester MeJA (referred to here collectively as jasmonate) are receiving renewed interest as potentially important signaling molecules in plants. This is because jasmonate markedly increases the expression of specific plant genes, some of which are wound responsive. Similarities with fatty acid-derived stress signaling molecules in animals (1) make jasmonate of general biological interest.

Survivorship And Recruitment In A Long-Lived Prairie Perennial, Ipomoea Leptophylla (Convolvulaceae), Kathleen H. Keeler

School of Biological Sciences: Faculty Publications

Little is known of the lifespans of herbaceous plants, especially in grasslands, although this information is basic to understanding the dynamics of species and ecosystems. Permanently marked plants of the bush morning glory, Ipomoea leptophylla (Convolvulaceae), in Nebraska sandhills prairie were censused annually from 1979-1989. While the average annual death rate was 2.6 per 100, virtually all the mortality was among smaller and probably younger plants. Recruitment varied greatly among years. Of plants of known age, the median age at first flowering was 6 yr. After 9 yr 30% had never flowered. Larger size classes flowered more frequently than smaller …

Origin And Evolution Of Defective Interfering Rnas Of Tomato Bushy Stunt Virus, David A. Knorr, Thomas Jack Morris

School of Biological Sciences: Faculty Publications

Viruses with defective genomes have been identified in association with virtually every major family of viruses and have been widely utilized as tools for investigating virus functions in animal cell culture systems (Perrault, 1981). It is generally thought that defective interfering viruses (DIs) arise through deletion, rearrangement, or recombination of a competent viral genome. DIs tack the ability for independent existence relying on their parental helper viruses to supply factors required for replication, maturation, and/or encapsidation (Huang and Baltimore, 1977). The interference attributed to DIs is thought to result from competition with the helper virus for factors required in trans …

Inheritance Of Acid-Soil Tolerance In Sorghum (Sorghum Bicolor) Grown On An Ultisol, C. I. Flores, L. M. Gourley, Jeffrey F. Pedersen, R. B. Clark

Department of Agronomy and Horticulture: Faculty Publications

Inheritance of acid-soil tolerance (generally considered AI-toxicity tolerance) i.n sorghum [Sorghum bicolor (L.) Moench] is not clear. Forty F₁ sorghum hybrids and their 14 parents were grown two seasons in the field at relatively high (67 and 71%) and low (43 and 42%) Al saturations on an acid Ultisol in Colombia, South America to evaluate the effects of acid soil on agronomic component traits and to better understand inheritance of acid-soil tolerance of sorghum. For plants grown at the high Al saturation levels, hybrids from acid-soil tolerant [AS-T] x acid soil-sensitive [AS-S] crosses were as tolerant as hybrids from …

Nitrogen And Methyl Jasmonate Induction Of Soybean Vegetative Storage Protein Genes, Paul E. Staswick, Jing-Feng Huang, Yoon Rhee

Department of Agronomy and Horticulture: Faculty Publications

Vegetative storage protein (VSP) and VSP mRNA levels in soybean (Glycine max) leaves correlated with the amount of NH₄NO₃ provided to nonnodulated plants. The mRNA level declined as leaves matured, but high levels of N delayed the decline. This is consistent with the proposed role for VSP in the temporary storage of N. Wounding, petiole girdling, and treatment with methyijasmonate (MeJA) increased VSP mRNA in leaves 24 hours after treatment. The magnitude of the response depended on leaf age and N availability. N deficiency essentially eliminated the response to wounding and petiole girdling. MeJA was …

Sterol Composition Of The Corn Root Lesion Nematode, Pratylenchus Agilis, And Corn Root Cultures, David J. Chitwood, William R. Lusby

Harold W. Manter Laboratory of Parasitology: Faculty Publications

Sterols from mixed stages of the com root lesion nematode, Pratylenchus agilis, and uninfected corn root cultures were analyzed by gas chromatography-mass spectrometry. Twenty-eight sterols were identified in P. agilis, including nine not previously detected in nematodes. The major sterols were 24-ethylcholest-22-enol, 24-ethylcholesta-5,22-dienol, 24-methy1cholestanol, 24-ethylcholestanol, isofucostanol, and 24-ethylcholesterol. The principal corn root sterols were 24-ethylcholesta-5,22-dienol, 24-methylcholesterol, 24-ethylcholesterol, isofucosterol, and cycloartenol. Therefore, the major metabolic transformation of sterols by P. agilis was saturation of the sterol nucleus. In addition, very small amounts of 4α-methylsterols were biosynthesized by P. agilis. The 4-methylation pathway is unique to nematodes and was …

Notes: Interpretive Analysis For Forage Yield Trial Data, Jeffrey F. Pedersen, K. J. Moore, Edzard Van Santen

Department of Agronomy and Horticulture: Faculty Publications

Forage cultivar evaluation is often done in small plots with multiple harvests throughout the growing season. Data is often summarized by presenting a yearly total yield for each cultivar in addition to the mean for each harvest date. Data summarization often becomes burdensome and difficult to interpret. Regressing yield against a growth index associated with harvest dates can be utilized to describe forage performance in a concise and easily interpreted format. Subsets of data from tall fescue (Festuca amndinacea Schreb.) yield trials conducted in Alabama and Kentucky were used to demonstrate the technique. The analysis involves regressing yield of a …

Fertility And Forage Yield Of Sorghum X Sudangrass Hybrids In A1 And A3 Cytoplasm, J. J. Toy, Jeffrey F. Pedersen, K. J. Moore

Department of Agronomy and Horticulture: Faculty Publications

Most sorghum x sudangrass hybrids are currently produced in Al male-sterile cytoplasm. Availability of alternative cytoplasmic sterility systems allows production of sorghum x sudangrass hybrids that may have superior forage characteristics. A study was conducted to compare the agronomic performance of Al and A3 sorghum x sudangrass hybrids. A bulk of eight sudangrass populations was used to pollinate four grain sorghum inbreds normally used as females that had been sterilized in both Al and A3 cytoplasm, and two inbreds normally used as males that had been sterilized in A3 cytoplasm. The hybrids were evaluated in 1990. Results indicate that male-sterile …

Distribution Of Polyploid Variation In Big Bluestem (Andropogon Gerardii, Poaceae) Across The Tallgrass Prairie Region, Kathleen H. Keeler

Kathleen H. Keeler Publications

The objective of this research was to describe the distribution of polyploid cytotypes of the grass big bluestem (Andropogon gerardii Vitman) along an east-west transect across the tallgrass prairie region, as an integral part of understanding the function of intraspecific polyploid polymorphism. Andropogon gerardii shows intraspecific variation in amount of nuclear DNA as a result of intraspecific poly-ploidy. Nearly 600 plants from 15 prairies in 5 states were collected and nuclear DNA was determined by flow cytometry. In the eastern part of the tallgrass prairie region, higher polyploids were rarely found. However, at the western edge of the tallgrass …

Fescues With Large Roots Are Drought Tolerant, H. A. Torbert, J. H. Edwards, Jeffrey F. Pedersen

Department of Agronomy and Horticulture: Faculty Publications

Consideration of root/soil interactions is essential in, adapting tall fescue (Festuca arundinacea Schreb.) to soil and climatic conditions of the Coastal Plain region of the southeast. Sandy soils of the region are very susceptible to the formation of hardpans. These compacted layers often restrict plant root development to the plow layer (0 to 6 in.) and prevent plant roots from reaching available moisture and nutrients in the subsoil horizons. Plants grown under these conditions are shallow rooted and will be subjected to water stress up to 50% of the time during the growing season. Although implements are available to penetrate …