Measurement of evaporation from adjuvant solutions using a volumetric method

Various agricultural spray adjuvants are available which are classified as anti-evaporants. This quality has the potential to aid in reducing drift and chemical evaporation and so improving coverage. Numerous other adjuvants not claiming these benefits may have these characteristics which are not being exploited. In order to assess these qualities, a simple, rapid assay was devised for measuring relative evaporation rates from individual drops. This method was then used to measure the evaporation rates of a variety of adjuvants under controlled temperature and humidity conditions. The droplet producing device uses a microliter syringe to dispense a droplet of known size. After a given period of time, the drop is taken back into the syringe and the volume lost to evaporation calculated. Modifications to the original device include suspending the drop inside a temperature- and humidity-controlled chamber. The original device was used for determining the rate of evaporation from water drops later than 0.3 mm. We have extended the use of the device to measure the rates of evaporation from a range of adjuvant solutions under controlled temperature and humidity conditions. The data reported here suggest that this method (a) is suitable for measuring evaporation from drops of many (but not all) adjuvant formulations, (b) is capable of discerning differences in relative rates of evaporation and (c) may be used for an array of adjuvant, drop size, and meteorological conditions. Major limitations appear to be (1) equilibrium surface tension, solutions having values less than c.35 mN m ?1 are difficult to analyze and (2) a lower limit on drop-size of c.300 μm.     

Calibrating the pesticide capture efficiency of passive dosimeters

A system has been devised for determining the absolute capture efficiency of passive dosimeters. The system is composed of three components: a wind tunnel, a tracer atomizer, and a capture efficiency test device (CETD). The CETD consists of a series of cylinders separated by nylon screens to intercept and capture the spray containing a tracer. The decline in tracer at the screens was used to determine the tracer incident on the first screen. This in turn was used to estimate the tracer incident on a test dosimeter of washed muslin. The capture efficiency of the dosimeter was expressed as the ratio of tracer captured to tracer incident on the dosimeter. The capture efficiency of the test dosimeter using the CETD was found to be independent of the time of exposure and quantity of tracer captured. The approach presented is novel in that the method for documenting capture efficiency does not require prior knowledge of the spray concentration. Elimination of this requirement allows the use of the device in a much larger array of test situations (e.g. field and greenhouse studies) than has been previously possible. Furthermore, the conceptual model can easily be modified to allow for capture efficiency measurements from a range of structures and materials such as plants or whole leaves, as well as insects and non-target animal species. The CETD is simple and portable and could be used to calibrate dosimeters in a variety of field situations.     

Pollen fertility among BC2 offspring of Impatiens interspecific hybrids of New Guinea and Indonesian ancestry

BC_T2 seedlings, derived from the cross Tangeglow (I. hawkeri Bull. × I. aurantiaca Teysm.) × 7851-1 (I. hawkeri Bull. × I. platypetala Lindl.) with 7851-1 as recurrent parent, were tested for presence of pollen fertility. Of 59 BC₂ seedlings, 11 were capable of in vitro pollen germination and also of effecting fertilization and subsequent seed set as pollen parent when crossed with Tangeglow as the seed-parent tester. The Spearman's rank correlation coefficient [r_s] of + 0.63 indicated a moderately good correlation of seedling ranking, based on pollen germination percent in vitro and seed set in vivo. Pollen germination of the 11 pollen-fertile BC₂ seedlings varied from a mean low of 4% to a mean high of 41%. The 3 highest pollen-germinating BC₂ seedlings also had the highest seed sets, but siblings showed a wide range in pollen-germinating ability. The best pollen germination for a seedling was 8% in the BC₁ and 41% in the BC₂. Pollen fertility in the BC₂ is discussed in relation to using interspecific hybridization in an Impatiens breeding program. This revised version was published online in August 2006 with corrections to the Cover Date.     

Shifting perceptions of rapid temperature changes’ effects on marine fisheries, 1945–2017

Climate‐driven warming has both social and ecological effects on marine fisheries. While recent changes due to anthropogenic global warming have been documented, similar basin‐wide changes have occurred in the past due to natural temperature fluctuations. Here, we document the effects of rapidly changing water temperatures along the United States’ east coast using observations from fisheries newspapers during a warming phase (1945–1951) and subsequent cooling phase (1952–1960) of the Atlantic Multidecadal Oscillation, which we compared to similar recent observations of warming waters (1998–2017). Historical warming and cooling events affected the abundance of species targeted by fishing, the prevalence of novel and invasive species, and physical access to targeted species. Fishing communities viewed historical cooling waters twice as negatively as they did warming waters (72% vs. 35% of observations). Colder waters were associated with a decrease in fishing opportunity due to storminess, while warming waters were associated with the potential for new fisheries. In contrast, recent warming waters were viewed as strongly negative by fishing communities (72% of observations), associated with disease, reductions in abundances of target species, and shifts in distributions across jurisdictional lines. This increasing perception that warming negatively affects local fisheries may be due to an overall reduction of opportunity in fisheries over the past half century, an awareness of the relative severity of warming today, larger changes in American culture, or a combination of these factors. Negative perceptions of recent warming waters’ effects on fisheries suggest that fishing communities are currently finding the prospect of climate adaptation difficult.     

Plant speciation

Like the formation of animal species, plant speciation is characterized by the evolution of barriers to genetic exchange between previously interbreeding populations. Prezygotic barriers, which impede mating or fertilization between species, typically contribute more to total reproductive isolation in plants than do postzygotic barriers, in which hybrid offspring are selected against. Adaptive divergence in response to ecological factors such as pollinators and habitat commonly drives the evolution of prezygotic barriers, but the evolutionary forces responsible for the development of intrinsic postzygotic barriers are virtually unknown and frequently result in polymorphism of incompatibility factors within species. Polyploid speciation, in which the entire genome is duplicated, is particularly frequent in plants, perhaps because polyploid plants often exhibit ecological differentiation, local dispersal, high fecundity, perennial life history, and self-fertilization or asexual reproduction. Finally, species richness in plants is correlated with many biological and geohistorical factors, most of which increase ecological opportunities.     

Crystal structure of osmylated c60: confirmation of the soccer ball framework

An x-ray crystal structure that confirms the soccer ball-shaped carbon framework of C(60) (buckminsterfullerene) is reported. An osmyl unit was added to C(60) in order to break its pseudospherical symmetry and give an ordered crystal. The crystal structure of this derivative, C(60)(OsO(4))(4-tert-butylpyridine)(2), reveals atomic positions within the carbon cluster.     

Recently formed polyploid plants diversify at lower rates

Polyploidy, the doubling of genomic content, is a widespread feature, especially among plants, yet its macroevolutionary impacts are contentious. Traditionally, polyploidy has been considered an evolutionary dead end, whereas recent genomic studies suggest that polyploidy has been a key driver of macroevolutionary success. We examined the consequences of polyploidy on the time scale of genera across a diverse set of vascular plants, encompassing hundreds of inferred polyploidization events. Likelihood-based analyses indicate that polyploids generally exhibit lower speciation rates and higher extinction rates than diploids, providing the first quantitative corroboration of the dead-end hypothesis. The increased speciation rates of diploids can, in part, be ascribed to their capacity to speciate via polyploidy. Only particularly fit lineages of polyploids may persist to enjoy longer-term evolutionary success.     

Effect of maternal genotype on development ofPhaseolus vulgaris L. ×P. lunatus L. interspecific hybrid embryos

Summary CertainPhaseolus vulgaris L. ×P. lunatus L. crosses were performed to study the effect of maternal heterozygosity on development and growth of the interspecific hybrid embryos. Interspecific embryos had a much slower growth rate in vitro compared with embryos derived from self-pollination ofP. vulgaris parents. Thus, interspecific embryos could be identified by growth rate in vitro. TheP. vulgaris maternal genotype affected both the number and size of 15-day-old interspecific embryos. Specifically, 76 Spartan Arrow produced significantly more interspecific embryos than did Great Northern as the seed parent, while maternal intraspecific hybrids produced smaller embryos than did maternal pure lines. There were no reciprocal differences between hybrid maternal parents for embryo number or size. Embryo size at excision and final size after culturing were closely correlated (r²=+0.93). The crossP. vulgaris 76 Spartan Arrow ×P. lunatus P.I. 214170 produced both the largest mean size at excision and the fastest growth in culture, indicating that specific combining ability affected both characteristics.Journal Paper No. J-12208 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2495     

A Bivalent Scale for Measuring Crowding Among Deer Hunters

One factor that may influence satisfaction in outdoor recreation is crowding, which historically has been defined as a negative evaluation of the density of other participants. While this definition is suitable for most scenarios, there are circumstances where encounters with others in the area are evaluated positively and thus contribute to the satisfaction of the participant. To adequately describe this phenomenon we suggest a more inclusive measurement of crowding that allows for both positive and negative evaluations of participant density to more accurately explore the relationship between crowding and satisfaction. We identified a sub-group of deer hunters who negatively evaluated the low density of other hunters, which reduced their satisfaction with their overall hunting experience. The methodology for measuring crowding in recreation research may have an important effect in identifying the relationship crowding has with other relevant variables as well as management implications.     

Crop domestication in the Compositae: a family-wide trait assessment

Despite current recognition as the largest family of flowering plants (23,000 species ± 1000; Anderberg et al. 2007), the Compositae is home to comparatively few important crop species. To assess domestication levels in the Compositae, we developed an index that categorizes taxa according to the strength of domestication. Most Compositae species that are used by humans exhibit little or no evidence of domestication and only a handful have been strongly domesticated. Although the Compositae (along with Orchidaceae) has few domesticated taxa compared to other large families such as Fabaceae or Poaceae, Compositae species have features that should make them suitable for domestication and human consumption. These include high species diversity, global geographic distribution, good seed storability, and good seed oil quality. We propose that the paucity of domesticated species in this family can be attributed to a variety of factors, chiefly the prevalence of secondary defence compounds, the lack of carbohydrates that can be digested by the human gut and the predominantly mechanical or wind-dependent seed dispersal syndrome. We also discuss the relevance of genetic and cultural factors. Although few Compositae crops currently play a major role in global agriculture, many species hold unexploited potential, especially as novel crops for food and industrial applications.