Search

Prairie junegrass [Koeleria macrantha (Ledeb.) Shultes] is a perennial, short-grass prairie species distributed throughout the Northern Hemisphere. This species demonstrates tolerance to many environmental stresses in Minnesota. Forty-eight K. macrantha accessions from the United States National Plant Germplasm System (NPGS) were grown under low-input conditions to evaluate turfgrass quality characteristics for use in a breeding program. A second objective was to identify key geographical locations for germplasm collection. The experiment was conducted at Becker and St. Paul, MN. Nineteen accessions at Becker and 30 accessions at St. Paul performed with an adequate turf quality rating of 5.0 or higher when averaged over the 3-yr study, suggesting the potential for use in low-input areas. Prairie junegrass from northern collection regions displayed the highest spring green-up ratings, an important turf trait in northern climates. There was a negative correlation between this trait and mowing quality at Becker (r = -0.44) and at St. Paul (r = -0.34). Several accessions had acceptable mowing quality and would be candidates for integration into a native prairie junegrass turfgrass breeding program. There was no correlation between inflorescence emergence and turf quality, or between inflorescence emergence and persistent straw suggesting that flowering does not necessarily affect turf quality ratings. Rust (unknown Puccinia species) was present at both locations. doi: 10.2135/cropsci2010.02.0068

Perennial ryegrass (Lolium perenne L.) is a cool-season turfgrass species that can exhibit significant freezing injury in northern climatic regions. The objective of this study was to quantify major physiological and biochemical changes occurring during the cold acclimation period in four perennial ryegrass accessions varying in freezing tolerance (two freezing-tolerant accessions, TOL-1 and TOL-2, and two freezing-susceptible accessions, SUS-1 and SUS-2). Plants were subjected to a cold acclimation period of 2[degrees]C for 21 d in a controlled environment chamber. Crown tissues were harvested at 0, 7, 14, and 21 d of acclimation for determination of proline, water soluble carbohydrates (WSC), and lipid composition. Leaf photochemical efficiency (Fv/Fm) was also measured weekly before plant sampling for biochemical components. In general, proline levels increased and Fv/Fm decreased during cold acclimation; however, there were no differences in proline accumulation or Fv/ Fm among the accessions in response to cold acclimation. Water soluble carbohydrates significantly increased in response to 2[degrees]C, with TOL accessions (TOL-1 and TOL-2) accumulating higher WSC than SUS (SUS-1 and SUS-2) by 21 d of acclimation. There were also significant changes in major phospholipids classes at 2[degrees]C. Specifically, TOL-2 exhibited a higher ratio of membrane stabilizing lipids and unsaturated fatty acid content compared to SUS-1, SUS-2, and TOL-1 by 21 d of cold acclimation. doi: 10.2135/cropsci2009.06.0293

Prairie junegrass [Koeleria macrantha (Ledeb.) Shult.] is a perennial, short-grass prairie species distributed throughout the northern hemisphere. This species is known to require fewer inputs than other cool-season turfgrasses and it demonstrates tolerance to many environmental stresses found in Minnesota. In June 2007, 48 K. macrantha accessions from the U.S. National Plant Germplasm System (NPGS) were grown and evaluated for seed production characteristics in 2 locations (St. Paul, MN, and Becker, MN). Significant variation was found among accessions for several seed production traits including harvest date, plant height, seedhead number, and seed yield. A significant correlation between seedhead number and seed yield was found, which can be utilized for indirect selection in the production nursery. Plant growth and seed yield were highest at the Becker location, demonstrating the species' preference for well-drained soils. Flowering times were significantly different between the locations; however, there were no significant differences in the duration from seedhead emergence to harvest between the locations. Multivariate analysis did not reveal clustering of accessions based on geographic origin, suggesting a diversity of material within collection regions. doi: 10.2135/cropsci2009.05.0235

Sellars and McDowell, among others, attribute a prominent role to the Myth of the Given. In this paper, I suggest that they have in mind two different versions of the Myth of the Given and I argue that Kant is not the target of one version and, though explicitly under attack from the other, has resources sufficient to mount a satisfactory response. What is essential to this response is a proper understanding of (empirical) concepts as involving unifying functions that can take sensations as input and deliver normative representations as outputs. By understanding concepts in this way, one need not, as the second version of the Myth of the Given maintains, take sensations to be both natural and normative. Instead, they can be understood as the natural effects of external objects on us, but natural effects that can nonetheless play a role in a normative process because the concepts that are responsible for the normativity of the results can require that such natural effects be present as inputs into the process.

The lack of winterhardiness of some cool-season grasses limit their usefulness in northern climates. Perennial ryegrass (Lofium perenne L.) lacks winterhardiness in Minnesota but has desirable qualities, such as wear tolerance and rapid establishment, that are useful in many turf applications. While domesticated germplasm may lack winterhardiness, undomesticated wild or landrace germplasm may have genes for better winterhardiness in environments like Minnesota's. In 2004, 300 accessions from two public sources in the USA were planted with eight check varieties and populations in two environments in central Minnesota, St. Paul and Becker. Thirty individuals of each accession were evaluated for seedling vigor and tiller survival after the first winter. Other turf-quality traits and tiller survival after the second winter were evaluated on those plants that survived the first winter. The first winter was extremely harsh and resulted in the death of all accessions and checks at Becker. There was good differentiation among accessions at St. Paul for tiller survival, with 8 of the 300 accessions performing better than NK200, the most winterhardy check variety. The second winter was considerably less harsh, with less death of tillers and whole plants. While the accessions do not have suitable turf quality for direct domestication, turf quality can be improved through breeding.

The primary limitation of tufted hairgrass [Deschampsia cespitosa (L.) E Beauv.] as a turfgrass appears to be damage caused by billbug (Sphenophorus spp.) herbivory. In this study several sets of germplasm were used in volatile collection studies. Whole-plant volatile collections were made on: i) untreated plants, ii) plants that had been treated with jasmonic acid (JA), and iii) plants that had experienced mechanical damage. In untreated plants, intraspecific differences were found for the amount of hexenyl acetate that was released; this compound has been shown to be involved in important plant volatile-insect interactions. Application of JA resulted in a dramatic increase in the production of monoterpenes, which are known to attract predators of insect pests. (Z)- [beta]-ocimene comprised nearly 9% of the total volatile profile after JA treatment, but was not detected in untreated plants. Mechanical damage of tufted hairgrass plants led to an increased release of characteristic green leaf volatiles such as 3-hexen-1-ol as well as hexenyl acetate. Mechanical damage changed the components of the volatile profile, but the results were quite different from JA treatment. It would be of interest to determine if the selection of tufted hairgrass germplasm that produces high and sustained levels of monoterpenes, in response to JA, would attract sufficient insect predators to make this an effective breeding strategy for insect resistance.

The rationalistic background of Kant's thought helps to explain his reception of Newton's laws of motion in relation to the justification of the laws of mechanics in Kant's 'Metaphysical Foundations of Natural Science' (1786). Topics include the status of the laws of motion in early 18th-century Germany, the first law of mechanics, the third law of mechanics, and action at a distance.

The relationship between Kant's 'Critique of Pure Reason' and his 'Metaphysical Foundations of Natural Science' has not been correctly understood. In the 'Metaphysical Foundations,' Kant gives a two-step argument concerning objects of outer sense. First he shows that the most basic feature of an object of outer sense must be to be movable in space. Then he uses the categorial headings of the first 'Critique' to derive additional determinations of objects of outer sense or matter. Michael Friedman's interpretation of the 'Metaphysical Foundations' is also discussed.

Turf‐type perennial ryegrass (Lolium perenne L.) success depends on adequate turfgrass quality and economical seed yield. In most breeding programs, spaced plants are the initial unit of selection in which observations of related individuals dictate the selection of superior germplasm for further testing. Therefore, spaced plants must be predictive of seed production and turfgrass growing environments. This study investigated the effectiveness of standard (three plants m−2) and competitive (23 plants m−2) spaced‐plant nurseries as selection environments with respect to two sward environments as well as applying a novel image analysis technique for several key traits. Seed production, turfgrass, and the two spaced‐plant growing environments were tested at two locations in Minnesota. Turfgrass quality traits were measured in 2017 and 2018 and seed production traits were measured in 2018. Automated image analysis was able to predict the traditional visual scoring values at both locations for crown rust (Puccinia coronata f.sp. lolii) severity [Pearson's correlation (rp) > 0.79, P <.001], winter injury (rp > 0.89, P <.001), and turfgrass texture (rp > 0.88, P <.001). Increasing the competition among spaced plants altered the plant phenotype and improved accuracy for vegetative biomass, crown rust severity, seed yield, and, at one location, turfgrass quality. There was no benefit of increasing competition for several traits such as genetic color, fertile tillers, and spikelet number. Although the competitive design was not useful for all traits, pragmatically, the competitive design used less space and often made measurements and observations easier for bunch‐type grasses. [ABSTRACT FROM AUTHOR]