Woody plant secondary chemicals increase in response to abundant deer and arrival of invasive plants in suburban forests

Plants in suburban forests of eastern North America face the dual stressors of high white-tailed deer density and invasion by nonindigenous plants. The combination of chronic deer herbivory and strong competition from invasive plants could alter a plant’s stress- and defense-related secondary chemistry, especially for long-lived juvenile trees in the understory, but this has not been studied. We measured foliar total antioxidants, phenolics, and flavonoids in juveniles of two native trees, Fraxinus pennsylvanica (green ash) and Fagus grandifolia (American beech), growing in six forests in the suburban landscape of central New Jersey, USA. The trees grew in experimental plots that had been subject for 2.5 years to factorial treatments of deer access/exclosure X addition/no addition of the nonindigenous invasive grass Microstegium vimineum (Japanese stiltgrass). As other hypothesized drivers of plant secondary chemistry, we also measured non-stiltgrass herb layer cover, light levels, and water availability. Univariate mixed model analysis of the deer and stiltgrass effects and multivariate structural equation modeling (SEM) of all variables showed that both greater stiltgrass cover and greater deer pressure induced antioxidants, phenolics, and flavonoids, with some variation between species. Deer were generally the stronger factor, and stiltgrass effects were most apparent at high stiltgrass density. SEM also revealed that soil dryness directly increased the chemicals; deer had additional positive, but indirect, effects via influence on the soil; in beech PAR positively affected flavonoids; and herb layer cover had no effect. Juvenile trees’ chemical defense/stress responses to deer and invasive plants can be protective, but also could have a physiological cost, with negative consequences for recruitment to the canopy. Ecological implications for species and their communities will depend on costs and benefits of stress/defense chemistry in the specific environmental context, particularly with respect to invasive plant competitiveness, extent of invasion, local deer density, and deer browse preferences.

Difficult Topics in the Chemistry Curriculum – Bulgarian Students‘ View

Chemistry is often considered a difficult subject, and the way students perceive learning affects their achievements. The research aims to identify: the topics in the secondary Chemistry curriculum perceived as difficult and as interesting by the Bulgarian students, the reasons for students’ difficulties and ways to overcome it. An inquiry was conducted with 321 students aged 16 – 17 years. According to them, the most difficult topics are Organic Chemistry and Chemical calculations (abstract and requiring specific skills). The most interesting topics are Organic Chemistry and Theory of Electrolytic Dissociation. Acids and bases. There is no significant correlation between levels of perceived difficulty and interest. Students relate difficulties to: information overload, emphasis on memorization, and lack of connections to everyday life. More lab activities and the practical application of the knowledge are recommended. Our research results can help improve Chemistry curricula and teaching practice.

Alien woody plants are more versatile than native, but both share similar therapeutic redundancy in South Africa

Understanding why alien plant species are incorporated into the medicinal flora in several local communities is central to invasion biology and ethnobiology. Theories suggest that alien plants are incorporated in local pharmacopoeias because they are more versatile or contribute unique secondary chemistry which make them less therapeutically redundant, or simply because they are locally more abundant than native species. However, a lack of a comprehensive test of these hypotheses limits our understanding of the dynamics of plants knowledge, use and potential implications for invasion. Here, we tested the predictions of several of these hypotheses using a unique dataset on the woody medicinal flora of southern Africa. We found that the size of a plant family predicts the number of medicinal plants in that family, a support for the non-random hypothesis of medicinal plant selection. However, we found no support for the diversification hypothesis: i) both alien and native plants were used in the treatment of similar diseases; ii) significantly more native species than alien contribute to disease treatments particularly of parasitic infections and obstetric-gynecological diseases, and iii) alien and native species share similar therapeutic redundancy. However, we found support for the versatility hypothesis, i.e., alien plants were more versatile than natives. These findings imply that, although alien plant species are not therapeutically unique, they do provide more uses than native plants (versatility), thus suggesting that they may not have been introduced primarily for therapeutic reasons. We call for similar studies to be carried out on alien herbaceous plants for a broader understanding of the integration of alien plants into the pharmacopoeias of the receiving communities.

Climate and Competitive Status Modulate the Variation in Secondary Metabolites More in Leaves Than in Fine Roots of Betula pendula

Plant secondary metabolites have many important functions; they also determine the productivity and resilience of trees under climate change. The effects of environmental factors on secondary metabolites are much better understood in above-ground than in below-ground part of the tree. Competition is a crucial biotic stress factor, but little is known about the interaction effect of climate and competition on the secondary chemistry of trees. Moreover, competition effect is usually overlooked when analyzing the sources of variation in the secondary chemistry. Our aim was to clarify the effects of competitive status, within-crown light environment, and climate on the secondary chemistry of silver birch (Betula pendula Roth). We sampled leaves (from upper and lower crown) and fine roots from competitively dominant and suppressed B. pendula trees in plantations along a latitudinal gradient (56–67° N) in Fennoscandia, with mean annual temperature (MAT) range: −1 to 8°C. Secondary metabolites in leaves (SML) and fine roots (SMFR) were determined with an HPLC-qTOF mass spectrometer. We found that SML content increased significantly with MAT. The effect of competitive stress on SML strengthened in colder climates (MAT<4°C). Competition and shade initiated a few similar responses in SML. SMFR varied less with MAT. Suppressed trees allocated relatively more resources to SML in warmer climates and to SMFR in colder ones. Our study revealed that the content and profile of secondary metabolites (mostly phenolic defense compounds and growth regulators) in leaves of B. pendula varied with climate and reflected the trees’ defense requirements against herbivory, exposure to irradiance, and competitive status (resource supply). The metabolic profile of fine roots reflected, besides defense requirements, also different below-ground competition strategies in warmer and colder climates. An increase in carbon assimilation to secondary compounds can be expected at northern latitudes due to climate change.

Students’ use of Justifications in Socioscientific Argumentation

Research focusing on students’ argumentation in socioscientific issues (SSI) shows that students tend to base their arguments on values rather than knowledge. This study explores Swedish upper secondary chemistry students’ written argumentation. The data consists of student texts written at the end of an intervention designed to develop skills related to high quality argumentation. The results show that after being taught about argumentation and the context of SSI, students mainly base their arguments on content knowledge. Value justifications are present in students’ texts, but constitute a smaller proportion. Beside content knowledge- and value justifications, we found a third category – “reasoning” – in which students draw conclusions, or make predictions of future events, to support or refute a claim. The justifications in the argumentative texts include a breadth of subject areas in which chemistry knowledge plays an important role. This study suggests that content knowledge constitutes an important part in student argumentation.

Scrum methodology in context-based secondary chemistry classes: effects on students’ achievement and on students’ perceptions of affective and metacognitive dimensions of their learning

Teaching with Scrum methodology includes ceremonies, roles and artefacts supporting students in planning, monitoring and directing their learning process. It scaffolds students’ learning in complex and sometimes overwhelming context-based learning environments. Effects of the implementation on both students’ learning outcomes and self-reported perceptions of six affective and metacognitive outcomes were investigated. Six teachers implemented Scrum methodology in a context-based secondary chemistry module on Green Chemistry. Their classes formed the experimental group. Based on how students experienced the quality of the implementation, teachers of the experimental group were subdivided into top-teachers and growth-teachers. Consequently, their students formed two sub-experimental groups. The comparison group, which did not use Scrum methodology, consisted of students taught by four teachers. A pre-test post-test control group design was used to study its effect on students’ achievements and self-reported affective and metacognitive outcomes. Students of both experimental groups outperformed students of the comparison group with a large effect-size (top-teachers); and medium effect-size (growth-teachers) on learning outcomes. Findings on students’ perceptions of affective and metacognitive outcomes revealed medium and small effects of Scrum methodology. Despite the fact that the implementation is challenging for teachers, it appears that Scrum methodology has positive effects on students’ achievement and on students’ perceptions of affective and metacognitive dimensions of their learning.

Phytochemistry reflects different evolutionary history in traditional classes versus specialized structural motifs

Foundational hypotheses addressing plant–insect codiversification and plant defense theory typically assume a macroevolutionary pattern whereby closely related plants have similar chemical profiles. However, numerous studies have documented variation in the degree of phytochemical trait lability, raising the possibility that phytochemical evolution is more nuanced than initially assumed. We utilize proton nuclear magnetic resonance (1H NMR) data, chemical classification, and double digest restriction-site associated DNA sequencing (ddRADseq) to resolve evolutionary relationships and characterize the evolution of secondary chemistry in the Neotropical plant clade Radula (Piper; Piperaceae). Sequencing data substantially improved phylogenetic resolution relative to past studies, and spectroscopic characterization revealed the presence of 35 metabolite classes. Metabolite classes displayed phylogenetic signal, whereas the crude 1H NMR spectra featured little evidence of phylogenetic signal in multivariate tests of chemical resonances. Evolutionary correlations were detected in two pairs of compound classes (flavonoids with chalcones; p-alkenyl phenols with kavalactones), where the gain or loss of a class was dependent on the other’s state. Overall, the evolution of secondary chemistry in Radula is characterized by strong phylogenetic signal of traditional compound classes and weak phylogenetic signal of specialized chemical motifs, consistent with both classic evolutionary hypotheses and recent examinations of phytochemical evolution in young lineages.

Investigation of Most Commonly Used Instructional Methods in Teaching Chemistry: Rwandan Lower Secondary Schools

Improved teaching methods facilitate the ease of acquisition of knowledge and lead to better achievement. The present study investigates the instructional methods most commonly used in teaching chemistry in lower secondary schools in Rwanda. SPSS 23.0 was used to analyze data from a survey conducted on 51 lower secondary chemistry teachers. The survey has satisfactory and acceptable reliability (Cronbach alpha=0.913 for 57 items on average). The results revealed that teachers prefer active learning methods though they still use traditional teaching methods. Comparison of teachers’ responses in terms of experience showed no statistically significant difference with p= 0.064. The study also found that some teachers have misconceptions in differentiating instructional approaches, methods, and techniques or strategies. Therefore, it is recommended that educational stakeholders should plan pieces of training to teachers about different instructional methods and techniques to use in chemistry teaching for effective learning outcomes.

Role of Workbooks and Teacher’s Books in Lower-secondary Chemistry Education in Czechia

Textbooks as a prominent product of educational content’s didactical transformation are usually published as a series. Textbooks are often accompanied by workbooks and teacher’s books. These publications are designed to support teacher’s work and can have a significant impact on the teaching practice. To deepen the understanding of chemical education at lower-secondary schools, the goal was to map chemistry teachers’ use of workbooks and teacher’s books. An electronic questionnaire containing close-ended questions as well as scales was used for this purpose. Information about workbooks and teacher’s books’ use, frequency of use, perceived importance and purpose were gathered. Whereas 63% of the 387 respondents reported using workbooks they consider important for the quality of education, teacher’s books are only used by 24% of teachers, with only 4% reporting their frequent use. The results indicate that workbooks are mostly used during chemistry lessons or for student homework, however a significant share of teachers mentioned using them for lesson preparation. The absence of a teacher’s book, coupled with the teachers’ reluctance to use them even when available, also pointed to their approach to teaching preparation based on the search for educational content and specific activities rather than methodological support in a broader sense.

Evaluation of the Chemistry curriculum at the lower secondary level: feedback from educators

Mauritius is presently witnessing a major educational reform, which has necessitated a review of the lower secondary curriculum in all subjects, including Science. Educators were called to evaluate the Science curriculum (which includes Biology, Chemistry and Physics components) by providing feedback on the curriculum content and content organisation. One hundred and thirty-three educators took part in this exercise. This paper focuses on a detailed analysis of the feedback obtained from educators regarding the lower secondary Chemistry curriculum (LSCC) to identify the challenges encountered in its implementation. The Process component of the Stufflebeam’s (Stufflebeam DL. The CIPP model for evaluation. In: Evaluation models. Dordrecht: Springer; 2000:279–317 pp) Context, Input, Process and Product (CIPP) Evaluation model has been used as a framework for the study. Based on qualitative thematic analysis, four main challenges were identified in the implementation of the LSCC namely, ensuring curriculum continuity, avoiding curriculum overload, the need for more laboratory experiences and knowledge transfer.