Jason G. Hamilton

Anthropogenic Changes in Tropospheric Composition Increase Susceptibility of Soybean to Insect Herbivory

Abstract Increased concentrations of CO2 and ozone are predicted to lower nutritional quality of leaves for insect herbivores, which may increase herbivory as insects eat more to meet their nutritional demands. To test this prediction, we measured levels of herbivory in soybean grown in ambient air and air enriched with CO2 or O3 using free air gas concentration enrichment (FACE). Under open-air conditions and exposure to the full insect community, elevated [CO2] increased the susceptibility of soybeans to herbivory early in the season, whereas exposure to elevated [O3] seemed to have no effect. In the region of the canopy exposed to high levels of herbivory, the percentage of leaf area removed increased from 5 to >11% at elevated [CO2]. We found no evidence for compensatory feeding at elevated [CO2] where leaf nitrogen content and C:N ratio were unaltered in plants experiencing increased herbivory. However, levels of leaf sugars were increased by 31% at elevated [CO2] and coincided with a significant increase in the density of the invasive species Popillia japonica Newman (Japanese beetle). In two-choice feeding trials, Japanese beetles and Mexican bean beetles (Epilachna varivestis Mulsant.) preferred foliage grown at elevated [CO2] to foliage grown at ambient [CO2]. These data support the hypothesis that the increased level of sugar in leaves grown at elevated [CO2] may act as a phagostimulant for the Japanese beetle. If these results apply more widely to soybean production, the expectation of agricultural yield increases as a result of increasing elevated [CO2] may need to be reevaluated.

Herbivore‐specific elicitation of photosynthesis by mirid bug salivary secretions in the wild tobacco Nicotiana attenuata

Herbivory is thought to be detrimental to plant fitness and commonly results in a metabolic shift in the plant: photosynthetic processes are typically down-regulated, while resource allocation to defenses is increased in herbivore-attacked plants, resulting in fitness costs of induced plant responses. Wild tobacco, Nicotiana attenuata, attacked by Tupiocoris notatus mirid bugs becomes resistant against more damaging herbivores through mirid-induced direct and indirect defenses. However, mirid-induced resistance and tissue loss do not result in a reduction of plant fitness. These findings suggest induced metabolic responses allowing the plant to compensate for the lost tissue and resources allocated to defenses. While feeding by Manduca sexta larvae results in a strong down-regulation of photosynthesis, we demonstrate a specific induction of elevated photosynthetic activity in N. attenuata leaves by elicitors in mirid salivary secretions. The elevated CO(2) assimilation rate is sufficient to compensate for the loss of photosynthetically active tissue and balances the net photosynthesis of infested leaves. We discuss the observed increase in the plants primary metabolic activity as a mechanism that allows plants to alleviate negative fitness effects of mirid attack and mediates the vaccination effects that result in a net benefit in environments with multiple herbivores.

Foliage of Oaks Grown Under Elevated Co2 Reduces Performance of Antheraea polyphemus (Lepidoptera: Saturniidae)

Abstract To understand how the increase in atmospheric CO2 from human activity may affect leaf damage by forest insects, we examined host plant preference and larval performance of a generalist herbivore, Antheraea polyphemus Cram., that consumed foliage developed under ambient or elevated CO2. Larvae were fed leaves from Quercus alba L. and Quercus velutina Lam. grown under ambient or plus 200 μl/liter CO2 using free air carbon dioxide enrichment (FACE). Lower digestibility of foliage, greater protein precipitation capacity in frass, and lower nitrogen concentration of larvae indicate that growth under elevated CO2 reduced the food quality of oak leaves for caterpillars. Consuming leaves of either oak species grown under elevated CO2 slowed the rate of development of A. polyphemus larvae. When given a choice, A. polyphemus larvae preferred Q. velutina leaves grown under ambient CO2; feeding on foliage of this species grown under elevated CO2 led to reduced consumption, slower growth, and greater mortality. Larvae compensated for the lower digestibility of Q. alba leaves grown under elevated CO2 by increasing the efficiency of conversion of ingested food into larval mass. Despite equivalent consumption rates, larvae grew larger when they consumed Q. alba leaves grown under elevated compared with ambient CO2. Reduced consumption, slower growth rates, and increased mortality of insect larvae may explain lower total leaf damage observed previously in plots in this forest exposed to elevated CO2. By subtly altering aspects of leaf chemistry, the ever-increasing concentration of CO2 in the atmosphere will change the trophic dynamics in forest ecosystems.

Combined effects of elevated CO2 and natural climatic variation on leaf spot diseases of redbud and sweetgum trees.

Atmospheric CO(2) concentrations are predicted to double within the next century and alter climate regimes, yet the extent that these changes will affect plant diseases remains unclear. In this study conducted over five years, we assessed how elevated CO(2) and interannual climatic variability affect Cercospora leaf spot diseases of two deciduous trees. Climatic data varied considerably between the five years and altered disease expression. Disease incidence and severity for both species were greater in years with above average rainfall. In years with above average temperatures, disease incidence for Liquidambar styraciflua was decreased significantly. When significant changes did occur, disease incidence and severity always increased under elevated CO(2). Chlorophyll fluorescence imaging of leaves revealed that any visible increase in disease severity induced by elevated CO(2) was mitigated by higher photosynthetic efficiency in the remaining undamaged leaf tissue and in a halo surrounding lesions.

Sustainability themed problem solving in data structures and algorithms

During the past two years, we have been creating curricular material centered around complex problems rooted in sustainability. Since multi-disciplinary learning is one of our primary goals, these projects are most meaningful when they connect students from different disciplines working toward a common understanding. However, strong disciplinary components present in their solutions also allow us to frame these projects from strictly disciplinary perspectives. In this paper, we show how they can be used for increased engagement in the context of data structures and algorithms. We review two new ones to explore (i) the structural characteristics of the western part of the U.S. power-grid, and (ii) the effects of over-harvesting on fish stocks.

Use of satellite imagery in multidisciplinary projects

The most important problems of our century require collaborative work. Therefore, as educators, we must be producing individuals who understand how to communicate and work with professionals from other fields. In this paper, we outline our ongoing efforts in addressing this need, without compromising discipline specific qualities or goals. Specifically, we present a number of programming projects that fulfill curricular requirements as well as making students aware of the Science Technology Engineering and Math (STEM) context of their work.

Using sustainability themes and multidisciplinary approaches to enhance STEM education

Purpose – The purpose of this paper is to report on the Multidisciplinary Sustainability Education Project (MSEP) as a framework using sustainability-themed education modules to introduce students to the need for multidisciplinary approaches to solving twenty-first-century problems while retaining traditional course strengths and content. Design/methodology/approach – The MSEP uses sustainability-themed education models and a multidisciplinary approach to link courses across disciplines. Modules are identified by an overarching question with activities designed to address the overarching question from course-specific perspectives, resulting in students writing short technical reports summarizing their results. Students then read and evaluate technical reports from other classes, and complete a summary activity designed to connect perspectives from different disciplines. Findings – The multi-method assessment identified no loss or gain in discipline-specific learning; increased understanding about the char...

Go Figure: Calculus Students' Use of Figures and Graphs in Technical Report Writing

Understanding how to read and use graphs to communicate scientific and mathematical in-formation is critical for STEM majors, as well as an important part of quantitative literacy. Ourstudy suggests that first-semester calculus students do not know how to use graphs in a technicalreport without explicit instruction. Although not a surprising result, it leaves us wondering aboutwhen such skills are developed, and if calculus I is a place to start. Our work is now exploringthe potential benefit on students’ use of graphs by having them formally evaluate other students’reports.KEYWORDS: Calculus, Technical Writing, Quantitiative Literacy

Green light drives photosynthesis in mosses

Temperate forests are characterised by variable light quality (i.e. spectral composition of light) at or near the forest floor. These understory environments have a high concentration of green light, as red and blue light are preferentially absorbed by upper canopy leaves. Understory species may be well-adapted for using green light to drive photosynthesis. Angiosperms have been shown to use green light for photosynthesis, but this ability has not been demonstrated in shade-dwelling bryophytes. In this study, net photosynthetic rate (PN) of three temperate understory species of moss (Dichodontium pellucidum (Hedw.) Schimp., Leucobryum albidum (Brid. ex P.Beauv) Lindb. and Amblystegium serpens (Hedw.) Schimp.) was measured under green, red + blue, and red + blue + green light to assess green light use efficiency. All three species were capable of photosynthesising beyond their respiratory demands using solely green light, with higher green light use efficiency measured in plants collected from areas with greater canopy cover, suggesting growth in a green light concentrated environment increases green light use efficiency. Each species was also collected from sites differing in their degree of canopy cover and grown under three light treatments (high light, low light, and green light). Photosynthetic efficiency (chlorophyll fluorescence), tissue nitrogen and carbon isotope concentrations were assessed after a short growth period. Growth conditions had little effect on leaf chemistry and monochromatic green light did not significantly degrade photosynthetic efficiency. This study provides the first evidence to date of positive net ‘green light photosynthesis’ in mosses.

Figures and First Years: An Analysis of Calculus Students' Use of Figures in Technical Reports

This three-year study focused on first-year Calculus I students and their abilities to incorporate figures in technical reports. In each year, these calculus students wrote a technical report as part of the Polar Bear Module, an educational unit developed for use in partner courses in biology, computer science, mathematics, and physics as part of the Multidisciplinary Sustainability Education (MSE) project at Ithaca College. In the first year of the project, students received basic technical report guidelines. In year two, the report guidelines changed to include explicit language on how to incorporate figures. In year three, a grading rubric was added to the materials provided to one of the two classes. In all three years, the students performed below expectations in their use of graphs in their reports. Reviews of the figures in the 78 technical reports written by the 106 students showed repeated deficiencies in the figures and how the students used them in the discussion sections and in evidence-based arguments. In year three the student’s quantitative literacy (QL) skills were assessed using an extract from a QL assessment instrument published in Numeracy. The results indicated that the students could both read and interpret figures, suggesting that issues with QL were not the main contributor to student difficulty with written discussion about graphs. The study underscores the need that explicit instructional attention be given to developing student knowhow in the use of figures in technical reports.