Life Sciences Commons^™

Evidence For A Tryptophane Cycle In Neurospora, Francis A. Haskins, Herschel Mitchell

Department of Agronomy and Horticulture: Faculty Publications

The work of Snell on lactic acid bacteria provided the first evidence that anthranilic acid may act as a precursor to tryptophane in vivo. Since the strains of bacteria which utilize anthranilic acid in the place of tryptophane also use indole, it was not possible to establish the order in which these two precursors occurred. In 1943 Tatum, Bonner and Beadle found that anthranilic acid was accumulated in the culture medium by a Neurospora crassa mutant, strain 10575, which required either tryptophane or indole for growth. It was therefore indicated that anthranilic acid is a precursor to indole in …

Separation Of Enzymes On The Filter Paper Chromatopile, Herschel Mitchell, Malcom Gordon, Francis A. Haskins

Department of Agronomy and Horticulture: Faculty Publications

A recent report from this laboratory described a method for isolation of low molecular weight compounds by chromatography on a pile of filter paper disks (1). Preliminary experiments have now been completed on the application of this method to the separation of enzymes. It was expected that a mixture of enzymes could be placed near the top of a filter paper pile and fractionated by imposing a gradient (i.e. pH, organic solvent, or salt concentration) on the column, thus taking advantage of a continuous process. Following the observation of Tiselius (2) it also seemed probable that enzyme separations could be …

A Metabolic Relationship Between The Aromatic Amino Acids, Joseph F. Nyc, Francis A. Haskins, Herschel K. Mitchell

Department of Agronomy and Horticulture: Faculty Publications

The present work involves a further investigation of a Neurospora mutant, C-86, previously mentioned by Lein, Mitchell and Houlahan (1) as one that can utilize anthranilic acid, indole, tryptophan, kynurenine, 3-hydroxyanthranilic acid, and nicotinic acid as supplements for growth. Mutant C-86, when crossed to a “wild-type” strain, was found to differ from this wild type strain, with respect to tryptophan biosynthesis, by a mutation at a single locus. The evidence presented suggests the possibility of a common precursor to the aromatic amino acids.

Prairies And Pastures Of The Dissected Loess Plains Of Central Nebraska, J. E. Weaver, W. E. Bruner

Department of Agronomy and Horticulture: Faculty Publications

Table of Contents:
Introduction
Geology
Physiography
Climate
Soil
Holdrege Silt Loam
Colby Silt Loam
Analyses Of Soils
Erosion
Root Relations
Early Settlement And Land Use
Native Vegetation
Communities Or Types Of Prairie
Short-Grass Type
Mid- And Tall-Grass Type
Mixed Short And Taller Grasses
Western Wheat Grass Type
Resume Of Grasses
Forbs
Shrubs
Pastures
Early Survey
Later Survey
Weedy Annual Grasses
Native Forbs
Subseres
E X Perimental Pastures
Methods
Sheen Pasture
Grazing Types
Grazing In 1945
Grazing In 1946
Comparison Of Consumption And Yield
McCan Pasture
Grazing In 1945
Grazing In 1946
Grazing In 1947
Comparison Of Consumption And Yield
Summary …

Changes In Vegetation And Production Of Forage Resulting From Grazing Lowland Prairie, J. E. Weaver, R. W. Darland

Department of Agronomy and Horticulture: Faculty Publications

When the early settlers came to Iowa, Nebraska, and adjacent territory they entered an almost boundless sea of grass. Throughout the years the prairie has been largely broken for crop production, but even today there still remain considerable tracts of native grassland annually mowed for hay and far greater ones of native pasture (Weaver and Fitzpatrick, '34). Climax grassland when grazed lightly or moderately may retain essentially its natural composition over extremely long periods. It is only when grazing animals are circumscribed in their range by fences and when too large a population is thus confined for too long a …

A Method Of Measuring Vigor Of Range Grasses, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

After several years of intensive study of midwestern prairies, their degeneration under grazing was given careful consideration (Weaver and Fitzpatrick, '32, '34; Weaver and Hansen, '41). It was ascertained that the intelligent use or careless abuse of these grasslands had resulted in pastures and ranges which could logically be grouped into four classes. These were excellent, good, medium, and poor. The first consisted almost entirely of climax grasses and an abundance of nutritious forbs which, as is almost universally found, were of the highest grazing value (Bews, '29: 298). In good pastures many of these persisted, but there was a …

Reduction Of Un-Grazed Mixed Prairie To Short Grass As A Result Of Drought And Dust, F. W. Albertson, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

Table of Contents:

Introduction
Soil and Soil Moisture
Vegetation
Early Results Of Drought
Alternating Moist Periods And Drought (1935-1939)
Period Of Most Critical Drought
Beginning of Dominance of Short Grasses
Spreading Of Short Grasses (1941)
Continued Spreading of Short Grasses and Consolidation of the Cover
The Record From Quadrats
Literature Cited

Annual Increase Of Underground Materials In Three Range Grasses, J. E. Weaver, Ellen Zink

Department of Agronomy and Horticulture: Faculty Publications

Any thoughtful student who has seen the mellow, granular, fiber-filled soil of virgin midwestern prairie and the same soil that has been cropped with maize or wheat for only a decade has cause for deep concern. For the cropped soil has lost its mellowness, the granular structure of discrete crumbs has largely disappeared as has also the binding root fiber. The soil when dry is often like dust, dust that pours between the fingers and is dispersed by the wind before it reaches the ground. Throughout the Midwest soil drifting has greatly increased, and erosion by water has become accelerated …

Length Of Life Of Roots Of Ten Species Of Perennial Range And Pasture Grasses, J. E. Weaver, Ellen Zink

Department of Agronomy and Horticulture: Faculty Publications

It is well known that death of the tops of practically all prairie grasses occurs each fall in temperate grasslands where the soil is regularly frozen. Year after year new shoots replace the old ones in this vegetation of long- lived perennials. But as to what portion of the root system is retained and over what period of time, we are almost without information. This maintains despite the fact that much work has been done to increase our knowledge of the root systems of prairie grasses. Since the early studies of Weaver (6, 7) on their depth and lateral extent, …

Injury And Death Or Recovery Of Trees In Prairie Climate, F. W. Albertson, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

Several years of decreasing precipitation initiated the 7 years of drought. By midsummer of 1934 it vas clear that the prairie region of the Middle West was undergoing the greatest drought since the beginning of its recorded weather history. The 12 months following June, 1933, was the driest weather period ever recorded not only for the Dakotas, Minnesota, Nebraska, Iowa, Illinois, and Missouri, but also drought in Kansas, Oklahoma, and Colorado was very severe (Kincer 1934). This intensely dry period, as well as those in several of the following years was accompanied by record-breaking temperatures, extremely low humidities, and exceptionally …

A Seven-Year Quantitative Study Of Succession In Grassland, J. E. Weaver, W. E. Bruner

Department of Agronomy and Horticulture: Faculty Publications

The study of plant succession has contributed more than any other single line of investigation to a deeper insight into the nature of vegetation. Earlier studies of succession, especially in grassland, were largely those of the primary sere. But with the utilization of the prairies for grazing, and the abandonment of submarginal land after a short period of cropping, numerous investigations of secondary successions were made. The earlier studies have been discussed by Clements (1916) in "Plant Succession." Sampson's plant succession in relation to range management appeared in 1919. Many of the more recent investigations of subseres in grassland and …

Extent And Longevity Of The Seminal Roots Of Certain Grasses, J. E. Weaver, Ellen Zink

Department of Agronomy and Horticulture: Faculty Publications

Grasses possess two distinct root systems. The primary or seminal root system begins development immediately upon the germination of the seed and consists of one to several main roots and their branches, the number varying with the species. The young plant is entirely dependent upon this primary root system for water and soil nutrients. Later, especially during the period of tiller production, a secondary or nodal root system develops from the lower nodes of the parent culm and from the tillers. The seminal roots are often designated as temporary in general texts and even in special books on grasses. Hitchcock …

Yields And Consumption Of Forage In Three Pasture-Types: An Ecological Analysis, R. W. Darland, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

Native pastures in eastern Nebraska and adjacent states have undergone profound changes as a result of drought. Bluestems (Andropogon) and associated grasses have been thinned and weakened, although recovery has been marked since 1941. In many pastures they were replaced by western wheat grass (Agropyron smithii) or other invading species. In nearly all, wheat grass now occurs in considerable abundance. Kentucky bluegrass (Paa pratensis), into which many overgrazed native pastures had degenerated, was almost completely killed by the drought, or greatly damaged as in western Iowa. Despite these widespread changes, few studies have been made on the relative yields, preferences …

Nature And Degree Of Recovery Of Grassland From The Great Drought Of 1933 To 1940, F. W. Albertson, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

For eight years drought had prevailed in the mid- continental grasslands. The true prairie west of Minnesota, Iowa, and Missouri had been woefully depleted. Mixed prairie farther westward to the Rocky Mountains had been nearly or entirely destroyed. But now the parched soil was wet once more, wet to a depth of several feet. The hot dry air was now warm and moist. The terrible dust storms had ceased. A changed environment had come at last, for this was the end of the long period of drought. Thus, in 1941 the long delayed recovery of vegetation began. The nature of …

Grassland Patterns In 1940, J. E. Weaver, R. W. Darland

Department of Agronomy and Horticulture: Faculty Publications

Major changes in grassland have now been followed for a decade over a considerable portion of true prairie in Nebraska and Kansas. The replacement of portions of this association by mixed prairie has been described (Weaver, '43). This major change resulted from the enormous increase or invasion of western wheat grass (Agropyron smithii) and the development of an understory of blue grama (Bouteloua gracilis) or buffalo grass (Buchloe dactyloides). But numerous areas of true prairie were only partially occupied by western wheat grass. Nearly all of the original cover of bluestems and associated species, …

Effects Of Drought, Dust, And Intensity Of Grazing On Cover And Yield Of Short-Grass Pastures, F. W. Albertson, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

The vast range lands of western Kansas occupy approximately one half of that area. They are now recovering from the terrible destruction wrought by overgrazing, drought, and dust-burial during the past decade. Since grass is man's most powerful ally in soil and water conservation, since pastures are tremendously important as the cheapest and most satisfactory feed for cattle, and since the recovery of the western range is not only an economic problem of great importance but a phenomenon of outstanding ecological interest, the redevelopment of the plant cover warrants careful investigation.

Replacement Of True Prairie By Mixed Prairie In Eastern Nebraska And Kansas, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

Destruction of a portion of one plant association and its replacement by another has just been completed. This has occurred not as the result of man's interference with the vegetation nor the effect of his grazing animals. It has been due to a dry climatic cycle and has been accomplished within a period of seven years. The scene of action was the broad area on the western edge of true prairie in central Kansas, eastern Nebraska, and eastern South Dakota. It is distinctly east of the mixed prairie in the central portion of these states. Although the phenomenon was general …

Resurvey Of Grasses, Forbs, And Underground Plant Parts At The End Of The Great Drought, J. E. Weaver, F. W. Albertson

Department of Agronomy and Horticulture: Faculty Publications

Eight years have now passed since the fateful spring of 1934. The almost rainless March and April, the unusually high winds, and the great clouds of dust following two summers of decreasing precipitation, portended disaster. The intensity and duration of the drought and its appalling destruction have been studied from the beginning (Weaver, Stoddart, and Noll 1935) and several reports have recorded changes wrought in the native grass cover (Savage 1937; Weaver and Albertson 1936, 1939, 1940, 1940a). Drought began in great intensity a year earlier in the mixed prairie westward and south-westward. But previous to 1933, intensive studies had …

Relative Drought Resistance Of Seedlings Of Dominant Prairie Grasses, Irene Mueller, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

Recent study of the severe damage to native midwestern grasslands resulting from the great drought was fundamentally an investigation of drought resistance of the various species of dominant grasses and accompanying forbs (Weaver and Albertson, '39, '40). Studies extending throughout the entire eight- or nine-year period of drought, especially those concerned with recharting permanent plots, have resulted in an accumulation of evidence regarding relative drought resistance of the various species (Albertson and Weaver, '42). Extensive field studies on the role of seedlings in recovery of midwestern ranges from drought have added much information on this subject (Weaver and Mueller, '42). …

Role Of Seedlings In Recovery Of Midwestern Ranges From Drought, J. E. Weaver, Irene Mueller

Department of Agronomy and Horticulture: Faculty Publications

An extensive survey of the degree of deterioration of midwestern ranges was made in 1939 (Weaver and Albertson, '40). Decreases in the basal cover of the grasses from extreme drought, overstocking, and damage by dust were appalling. Basal cover of the native grass had decreased to 1 percent in one-fourth of the ranges examined and it was 21 percent or more in only 16 percent. Little, if any, improvement occurred during the following year; instead certain large areas suffered distinct losses as a result of severe late summer drought. The perennial grasses over large areas in southwestern Kansas, for example, …

Competition Of Western Wheat Grass With Relict Vegetation Of Prairie, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

Many profound changes in mid-continental grasslands have resulted from the recent extended drought. In the prairies of eastern Nebraska, Kansas and South Dakota, the earlier continuous stands of bluestem (Andropogon scoparius and A. furcatus) have often been greatly fragmented and now occur as relict patches a few square feet to many square rods in extent. Loss of approximately 95 per cent of little bluestem has left the prairie cover very open. Over large areas, except for weeds and a few surviving grasses and forbs, the soil was bared (Weaver, Stoddart and Noll, 1935; Weaver and Albertson, 1939). Grasses …

History Of The Native Vegetation Of Western Kansas During Seven Years Of Continuous Drought, F. W. Albertson, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

When the pioneers came from the East to make new homes in the Great Plains region, they found a dense cover of native vegetation. It was disturbed only by buffaloes, prairie dogs, other plains animals, Indians, and prairie fires. The Federal Government required that a certain amount of land be broken and put under cultivation, whether the land was obtained as a homestead or as a timber claim (McArdle and Costello, 1936).

The practice of the settlers was to break up a small tract of the prairie on which they could grow enough winter feed to sustain their cattle, horses, …

Regeneration Of Native Midwestern Pastures Under Protection, J. E. Weaver, W. W. Hansen

Department of Agronomy and Horticulture: Faculty Publications

The origin of native midwestern pastures from virgin prairie and the degeneration of the prairie under long-continued grazing have been outlined in some detail in a previous bulletin (Weaver & Hansen 1941). During the last four years much study has been given to the converse phenomenon of the regeneration of native midwestern pastures when grazing animals were excluded. This universal phenomenon of the return of vegetation to something of its former natural condition is summed up in the term plant succession (Clements 1928). In connection with pastures derived from true prairie, it is of great practical as well as scientific …

Native Midwestern Pastures: Their Origin, Composition, And Degeneration, J. E. Weaver, W. W. Hansen

Department of Agronomy and Horticulture: Faculty Publications

According to Doctor J. E. Weaver and Mr. W. W. Hansen the purpose of this bulletin is to present certain facts involved in range and pasture management by outlining in some detail the fundamental phenomenon of vegetational change upon which all rational pasture studies must be based. They maintain that the native prairie vegetation is an organic entity in close adjustment with soil and climate, which has developed gradually to its present condition of dynamic stabilization. When the prairie is grazed and trampled, various changes occur, the nature and extent of which vary somewhat directly with the degree of disturbance, …

Occurrence Of A Disease Of Side-Oats Grama, R. L. Fowler, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

The beginning of a disease of Boateloua curtipendula, first observed in 1937 but occurring in alarming proportions in 1939, is of much interest. The fact that this grass has increased greatly during the past six years, from a rank of seventh or eighth among dominants of true prairie to one of the two or three most important species, adds unusual economic interest. Moreover, side-oats grama not only has very wide distribution and is being grown abundantly in grass nurseries of the Soil Conservation Service but also it is one of the most drought-resistant among the best grasses for rejuvenating …

Deterioration Of Midwestern Ranges, J. E. Weaver, F. W. Albertson

Department of Agronomy and Horticulture: Faculty Publications

The native grasses of the mixed prairie and short-grass plains disclimax have been subjected for a long period of years to extreme drought, much overstocking, and severe damage from dust. Behavior of the vegetation during the dry year of 1933, the extreme drought of 1934, and the terrible dust storms and intermittent periods of desiccation during subsequent years, has been continuously observed (Weaver and Albertson, '36). Previous studies in this area furnished a back- ground which enabled one to compare present conditions with those of the pre-drought period (Weaver, '24; Clements and Weaver, '24; Albertson, '37). A large series of …

The Genetics Congress, R. A. Emerson

Department of Agronomy and Horticulture: Faculty Publications

Mice and men reported from

Edinburgh after the Congress

(JOURNAL OF HEREDITY for

September 1939) but since then there

has been silence, as far as getting into the

record any details of the Congress. On

account of the disruption to trans-Atlantic

travel caused by the declaration of

war between England and Germany,

September 3, the American delegation to

the Congress was considerably delayed

in getting back. Only two failed ultimately

to return, Dr. and Mrs. F. W.

Tinney of the Division of Farm Crops

of the University of Wisconsin. They

were among about a dozen members of

the Congress who …

Deterioration Of Grassland From Stability To Denudation With Decrease In Soil Moisture, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

The great drought has now prevailed intermittently in the mid- west for a period of seven years. Damage to native vegetation in 1934 has been partially repaired, but further destruction has also occurred. Continued study of the shiftings in dominance among the grasses has revealed widespread losses of certain species and partial or complete replacement by others. Forbs also have greatly diminished, both in number of species and in abundance, and changes in structure of vegetation generally have been pronounced (3, 4). Hence it seemed advisable during 1939 to study the degree of deterioration of the grasslands, if any, from …

Amount Of Underground Plant Materials In Different Grassland Climates, S. B. Shively, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

From the highlands of central Mexico entirely across the United States and northward into Canada extends the great midcontinental area of grassland. From this central mass, prairie extends westward across Wyoming into eastern Utah, and southwestward through northern New Mexico into northern Arizona. Other grasslands in the northwest cover most of southern Idaho, a part of northern Utah, large areas in eastern Oregon and Washington, and recur in British Columbia. The Pacific prairie occupies the Great Valley of California, and the Desert Plains grassland much of southern Arizona and New Mexico and southwestern Texas. Together they constitute the Grassland or …

Effects Of Frequent Clipping On The Underground Food Reserves Of Certain Prairie Grasses, F. S. Bukey, J. E. Weaver

Department of Agronomy and Horticulture: Faculty Publications

A series of experiments in which true-prairie grasses were clipped at frequent intervals afforded excellent materials for a study of the effects of such treatment upon the food reserves. Two species of Andropogon, at present the most important dominants of true prairie, were employed. A series of quadrats on a north-facing slope in the Blemont prairie in Lincoln, Nebraska, in which little bluestem Andropogon scoparius, grew in about 70 of big bluestem, A. furcatus, were obtained about a mile distant from virgin lowland prairie near the flood plain of salt creek.