Response of running buffalo clover (Trifolium stoloniferum Muhl ex. A. Eaton) to herbaceous competition and transplanting in Monongahela National Forest

Running buffalo clover (RBC) is a rare perennial plant that grows throughout the American Midwest and the Appalachian Mountains. It requires disturbed forests to establish and proliferate. It has been suggested that, in the past, these conditions were created by buffalo; now logging operations maintain RBC populations. However, forest managers have been looking for ways to create suitable habitat for RBC that do not involve harvesting practices. This could help create new populations in areas that cannot be logged. Once established, competing vegetation might influence RBC abundance and flowering. This study seeks to quantify this influence by measuring the vegetation in and around naturally occurring RBC patches. This study took place within five managed sites in the Cheat Wildlife Management Area within the Monongahela National Forest, WV. In these sites we completed an inventory of RBC patches, counting rosette numbers and flowers in each patch, and we collected data on neighboring trees. A year later, we returned to these patches and in the center 1 m2 counted RBC rosettes and estimated RBC cover and RBC maximum height. We also measured the cover of various vegetation types, and the height of the tallest vegetation. We found that RBC patch size was positively related to tree canopy cover, and RBC flowering was negatively correlated with the presence of nearby trees. We also found that RBC rosette density, cover, and height were positively correlated with forb cover, and negatively correlated with shrub/vine cover. In a separate experiment, we established new RBC occurrences by transplanting five individuals into 1-m2 experimental subplots with varying levels of prior ground disturbance. Treatments (n=15) comprised mowing vegetation, raking away litter, raking and mowing together, and undisturbed control. RBC survival rates in treated subplots one year after planting were increased by the disturbance treatments (83%) when compared to the control (57%). The number of rosettes that arose from each surviving transplant was also greater in the three disturbance treatments combined (P = 0.009) than the control, but there was no difference in the cover per surviving transplant (P = 0.23). Consequently, the total number of rosettes and their cover was greater after mowing and mowing+raking when compared with control. Raking alone resulted in values intermediate between the treatments involving raking and the control; values were not significantly different from the two raking treatments, but showed a statistical trend (P ≤ 0.1) of having a greater number of rosettes (but not cover). The results of this study will help managers identify suitable canopy and herb-layer conditions for RBC to thrive, as well as create habitat for RBC without the use of logging disturbances

Molecular responses to cadmium exposure in two contrasting durum wheat genotypes

Cadmium is a heavy metal that can be easily accumulated in durum wheat kernels and enter the human food chain. Two near-isogenic lines (NILs) with contrasting cadmium accumulation in grains, High-Cd or Low-Cd (H-Cd NIL and L-Cd NIL, respectively), were used to understand the Cd accumulation and transport mechanisms in durum wheat roots. Plants were cultivated in hydroponic solution, and cadmium concentrations in roots, shoots and grains were quantified. To evaluate the molecular mechanism activated in the two NILs, the transcriptomes of roots were analyzed. The observed response is complex and involves many genes and molecular mechanisms. We found that the gene sequences of two basic helix–loop–helix (bHLH) transcription factors (bHLH29 and bHLH38) differ between the two genotypes. In addition, the transporter Heavy Metal Tolerance 1 (HMT-1) is expressed only in the low-Cd genotype and many peroxidase genes are up-regulated only in the L-Cd NIL, suggesting ROS scavenging and root lignification as active responses to cadmium presence. Finally, we hypothesize that some aquaporins could enhance the Cd translocation from roots to shoots. The response to cadmium in durum wheat is therefore extremely complex and involves transcription factors, chelators, heavy metal transporters, peroxidases and aquaporins. All these new findings could help to elucidate the cadmium tolerance in wheat and address future breeding programs

What do Seniors Remember From Freshman Physics?

We have given a group of 56 MIT seniors who took mechanics as freshmen a written test similar to the final exam they took in their freshman course, plus the Mechanics Baseline Test (MBT) and Colorado Learning Attitudes about Science Survey (C‐LASS) standard instruments. Students in majors unrelated to physics scored 60% lower on the written analytic part of the final than they did as freshmen. The mean score of all students on conceptual multiple choice questions included on the final also declined by about 60% relative to the scores of freshmen. The mean score of all participants on the MBT was insignificantly changed from the posttest taken as freshmen. More specifically, however, the students’ performance on 9 of the 26 MBT items (with 6 of the 9 involving graphical kinematics) represents a gain over their freshman pretest score (a normalized gain of about 70%, double the gain achieved in the freshman course alone), while their performance on the remaining 17 questions is best characterized as a loss of approximately 50% of the material learned in the freshman course. Attitudinal survey results indicate that almost half the seniors feel the specific mechanics course content is unlikely to be useful to them, a significant majority (75–85%) feel that physics does teach valuable skills, and an overwhelming majority believe that mechanics should remain a required course at MIT.National Science Foundation (U.S.

Modeling applied to problem solving

We describe a modeling approach to help students learn expert problem solving. Models are used to present and hierarchically organize the syllabus content and apply it to problem solving, but students do not develop and validate their own Models through guided discovery. Instead, students classify problems under the appropriate instructor‐generated Model by selecting a system to consider and describing the interactions that are relevant to that system. We believe that this explicit System, Interactions and Model (S.I.M.) problem modeling strategy represents a key simplification and clarification of the widely disseminated modeling approach originated by Hestenes and collaborators. Our narrower focus allows modeling physics to be integrated into (as opposed to replacing) a typical introductory college mechanics course, while preserving the emphasis on understanding systems and interactions that is the essence of modeling. We have employed the approach in a three‐week review course for MIT freshmen who received a D in the fall mechanics course with very encouraging results.National Science Foundation (U.S.

Secondary metabolites in xylella fastidiosa-plant interaction

During their evolutionary history, plants have evolved the ability to synthesize and accumulate small molecules known as secondary metabolites. These compounds are not essential in the primary cell functions but play a significant role in the plants’ adaptation to environmental changes and in overcoming stress. Their high concentrations may contribute to the resistance of the plants to the bacterium Xylella fastidiosa, which has recently re‐emerged as a plant pathogen of global importance. Although it is established in several areas globally and is considered one of the most dangerous plant pathogens, no cure has been developed due to the lack of effective bactericides and the difficulties in accessing the xylem vessels where the pathogen grows and produces cell aggregates and biofilm. This review highlights the role of secondary metabolites in the defense of the main economic hosts of X. fastidiosa and identifies how knowledge about biosynthetic pathways could improve our understanding of disease resistance. In addition, current developments in non-invasive techniques and strategies of combining molecular and physiological techniques are examined, in an attempt to identify new metabolic engineering options for plant defense

What Else (Besides the Syllabus) Should Students Learn in Introductory Physics?

We have surveyed what various groups of instructors and students think students should learn in introductory physics. We started with a Delphi Study based on interviews with experts, then developed orthogonal responses to “what should we teach non‐physics majors besides the current syllabus topics?” AAPT attendees, atomic researchers, and PERC08 attendees were asked for their selections. All instructors rated “sense‐making of the answer” very highly and expert problem solving highly. PERers favored epistemology over problem solving, and atomic researchers “physics comes from a few principles.” Students at three colleges had preferences anti‐aligned with their teachers, preferring more modern topics, and the relationship of physics to everyday life and also to society (the only choice with instructor agreement), but not problem solving or sense‐making. Conclusion #1: we must show students how old physics is relevant to their world. Conclusion #2: significant course reform must start by reaching consensus on what to teach and how to hold students’ interest (then discuss techniques to teach it).National Science Foundation (U.S.) (NSF grant PHY-0757931