Seedbed Effects on Grass Establishment on Abandoned Nebraska Sandhills Cropland

Perennial grass establishment on abandoned cropland in the Nebraska Sandhills difficult due to low soil fertility, organic matter, and water holding capacity and high potential erodibility. Establishment is further complicated by unpredictable precipitation and weed competition. Two warm-season grasses: sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern.] and switchgrass (Panicam virgatum L.); and 2 cool-season grasses: smooth brome (Bromus inermis Leyss.) and intermediate wheat-grass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey subsp. were evaluated with spring-seeded field trials. Seedbed preparation [untilled, disced, and dead oat (Avena sativa L.) cover (DOC)] effect on seeded grass and nonseeded species densities was evaluated in 1985 and 1986 at 2 locations on Valentine sands (Aquic Ustipsamment). In 1985 1 site was irrigated. Both sites were dryland in 1986. Stand failure (\u3c 5 seedlings/m2) occurred on the dryland rite in 1985 due to low, erratic precipitation. Stands evaluated in June 1986 on plots established with irrigation in 1985 had 38, 46, and 61 plants/m2 for the untilled, disced, and DOC seedbeds, respectively. The disced or DOC seedbeds were required for successful (\u3e plants/m2) dryland seedings in 1986 at both locations. Irrigation the establishment year minimized risk of stand failure and allowed the use of my seedbed preparation or grass species studied. Sand bluestem was the only species to establish both years. However, if a dryland seedling of a cool-season species is desired, intermediate wheatgrass appeared more adapted than smooth brome

Immunofluorescent Localization of RuBPCase in Degraded C\u3csub\u3e4\u3c/sub\u3e Grass Tissue

Digestion-resistant tissues found in C4 grasses may allow soluble protein to escape rumen degradation. The objective of this study was to use immunofluorescent localization to follow loss of ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPCase) from switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) parenchyma bundle sheath cells (BSC) during rumen degradation. Fluorescent signal was observed from switchgrass and big bluestem BSC through 24 and 16 h in situ digestion, respectively, and from BSC associated with both intact tissue fragments, and isolated vascular bundles in omasal digesta and fecal material from steers (Bos tarus L.) grazing switchgrass. Immunofluorescent localization demonstrated that in certain C4 grasses (i) parenchyma BSC can protect RuBPCase from degradation through 24-h in situ incubation, (ii) BSC containing RuBPCase can exit the rumen prior to degradation, and (iii) protein protected by BSC can escape degradation in the whole gastrointestinal tract and be excreted

Duplex DNA from Sites of Helicase-Polymerase Uncoupling Links Non-B DNA Structure Formation to Replicative Stress

BACKGROUND: Replication impediments can produce helicase-polymerase uncoupling allowing lagging strand synthesis to continue for as much as 6 kb from the site of the impediment. MATERIALS AND METHODS: We developed a cloning procedure designed to recover fragments from lagging strand near the helicase halt site. RESULTS: A total of 62% of clones from a p53-deficient tumor cell line (PC3) and 33% of the clones from a primary cell line (HPS-19I) were within 5 kb of a G-quadruplex forming sequence. Analyses of a RACK7 gene sequence, that was cloned multiple times from the PC3 line, revealed multiple deletions in region about 1 kb from the cloned region that was present in a non-B conformation. Sequences from the region formed G-quadruplex and i-motif structures under physiological conditions. CONCLUSION: Defects in components of non-B structure suppression systems (e.g. p53 helicase targeting) promote replication-linked damage selectively targeted to sequences prone to G-quadruplex and i-motif formation

Substitution of Cytosine with Guanylurea Decreases the Stability of i-Motif DNA

Both 5-aza-2′-deoxycytidine (decitabine) and its primary breakdown product, 2′-deoxyriboguanylurea (GuaUre-dR), have been shown to act as mutagens and epimutagens that cause replication stress and alter both DNA methylation and gene expression patterns. As cytosine analogues, both are expected to be preferentially incorporated into regions of GC skew where runs of cytosine residues are sequestered on one strand and guanine residues on the other. Given that such regions have been identified as sites with the potential for effects on gene expression and replication stress linked to formation of alternative DNA secondary structures, it is of interest to determine the influence that these base analogues might have on the stability of structures of this kind. Here we report that incorporation of GuaUre-dR into an i-motif-forming sequence decreases both the thermal and pH stability of an i-motif despite the apparent ability of GuaUre-dR to base pair with cytosine

Seeding Techniques for Alfalfa to Improve Subirrigated Meadows

Improving quality and quantity of forage harvested from poor condition, subirrigated hay meadows in the Nebraska Sand Hills is critical to the winter forage reserve of livestock producers. Alfalfa (Medicago sativa L.) is the most commonly used legume for meadow improvement. Broadcast seeding (11.2 kg/ha) was compared to sod seeding (11.2 kg/ha) as a method to introduce alfalfa into an alkaline subirrigated meadow (Fluvaquentic Haplustolls). Before seeding, the study area received 78.5 kg/ha phosphorous. Paraquat (0.29 kg/ha) was applied to one-half of the area to suppress plant competition and provide qualitative information on treatment consistency across a range of sod competition. Lo-till sod seeding was accomplished with a power tillage seeder. Seedling density was determined in spring the following year. Broadcast alfalfa had a greater seedling density than sod-seeded alfalfa (38.4 and 19.1 plants/m2, respectively, p=.09). Apparently, paraquat had no effect on seedling establishment and tended to reduce total yield. Yields the year of seeding, using a two harvest scheme, were greater for broadcast compared to sod-seeded alfalfa (p=.02). However, there was no significant difference between yields of broadcast alfalfa and control

Canopy Architecture and Morphology of Switchgrass Populations Differing in Forage Yield

Phenotypic selection has been used to improve forage yield and in vitro dry matter disappearance (IVDMD), but the effects on canopy architecture and morphology are not understood. Our objectives were to determine if canopy architecture and morphology can explain genotype x environment (G x E) yield differences in switchgrass (Panicum virgatum L.) and to evaluate canopy architecture and morphology as selection criteria for increasing yield. This study was conducted in 1993 near Mead, NE, and near Ames, IA. The experimental design was a randomized complete block experiment with a split-plot arrangement of four replicates at each location. Whole plots were tiller population and subplots were sward maturity. Tiller populations were harvested on 9 June, 19 July, and 27 August at Ames and on 10 June, 27 July, and 26 August at Mead and were classified morphologically. Tillers were separated into primary yield components and dried at 55°C to determine total forage yield and dry matter contribution of morphological components. Genotype x environment interactions occurred for total forage yield and tiller density. Previous phenotypic selection for increased forage yield and IVDMD apparently altered morphological changes within the canopy of selected switchgrass populations. The most apparent changes were development of additional collared leaves and internodes in some populations across locations. Although canopy architecture may not be a useful selection criterion because of variability associated with individual canopy traits, indirect measurements showed that leaf area index (LAI) has some potential as a selection criterion for increasing total forage yield. However, selection for individual canopy traits may be most effective for modifying sward growth habits

Fiber Digestion Dynamics of Sward Components within Switchgrass Populations

Forage quality as it relates to plant maturity is well established; however, strategies for improving fiber digestion in switchgrass populations have not been determined. The objectives of this study were to determine fiber digestion of sward components within switchgrass (Panicum virgatum L.) populations and which aspects of fiber digestion dynamics caused in vitro dry matter disappearance (IVDMD) differences of six switchgrass populations. This study was conducted in 1993 near Ames, IA, and Mead, NE. The experimental design was a randomized complete block design with a split-plot arrangement of treatments with four replicates at each location. Whole plots were populations and subplots were sward maturity. ‘Trailblazer’, ‘Pathfinder’, ‘Cave-in-Rock’, and three experimental switchgrass populations were used in this study. Populations were harvested on 9 June, 19 July, and 27 August at Ames and on 10 June, 27 July, and 26 August at Mead. Fiber composition and digestibility were determined on leaf blade, leaf sheath, and stem fractions of the primary growth stages. Significant differences for theoretical true digestibility (TD) and neutral detergent fiber (NDF) existed for morphological components at each sward maturity. However, digestion characteristics of the sward components were not stable across primary growth stages. Rate of fiber digestion was faster for most sward components at Ames than Mead, although stems of elongating tillers from elongating swards digested faster on plants grown at Mead than Ames. Rate of fiber digestion of stems was typically slower than either leaf blades or sheaths, but in several instances they were similar or stems had faster rates of fiber digestion. Although phenotypic selection can increase fiber digestibility, plant maturity remains an important factor, and selections may require evaluation at different stages of morphological development. Thus, improvements in forage digestion, at least in switchgrass, may only be manifested for the growth stage at which it was selected

Fiber Digestion Dynamics of Sward Components within Switchgrass Populations

Forage quality as it relates to plant maturity is well established; however, strategies for improving fiber digestion in switchgrass populations have not been determined. The objectives of this study were to determine fiber digestion of sward components within switchgrass (Panicum virgatum L.) populations and which aspects of fiber digestion dynamics caused in vitro dry matter disappearance (IVDMD) differences of six switchgrass populations. This study was conducted in 1993 near Ames, IA, and Mead, NE. The experimental design was a randomized complete block design with a split-plot arrangement of treatments with four replicates at each location. Whole plots were populations and subplots were sward maturity. ‘Trailblazer’, ‘Pathfinder’, ‘Cave-in-Rock’, and three experimental switchgrass populations were used in this study. Populations were harvested on 9 June, 19 July, and 27 August at Ames and on 10 June, 27 July, and 26 August at Mead. Fiber composition and digestibility were determined on leaf blade, leaf sheath, and stem fractions of the primary growth stages. Significant differences for theoretical true digestibility (TD) and neutral detergent fiber (NDF) existed for morphological components at each sward maturity. However, digestion characteristics of the sward components were not stable across primary growth stages. Rate of fiber digestion was faster for most sward components at Ames than Mead, although stems of elongating tillers from elongating swards digested faster on plants grown at Mead than Ames. Rate of fiber digestion of stems was typically slower than either leaf blades or sheaths, but in several instances they were similar or stems had faster rates of fiber digestion. Although phenotypic selection can increase fiber digestibility, plant maturity remains an important factor, and selections may require evaluation at different stages of morphological development. Thus, improvements in forage digestion, at least in switchgrass, may only be manifested for the growth stage at which it was selected