Speaking Practices Designed to Improve Presentation Skills and Their Effect on High School Students’ Oral Performance

この研究は，口頭発表活動に必要な技術を身につける実践を通じて，発話力の伸びを検証することを目的とした実証的研究である。高校１年生の実験クラスを対象に，物語の紹介を目的とする，パターン化された構成で行うプレゼンテーション形式の活動を一定期間行い，ポストテストにおける発話を統制クラスと比較した結果，流暢さの面で向上が見られた。実験クラスの経験した発表活動では，パターン化された情報構造で発話内容を考えるため，活動時の発話過程において，概念化の段階で受ける認知的負荷が軽減され，言語化に向ける認知資源を増やすことができ，流暢さが高まったと考えられる。The present study takes an empirical approach to assessing the effect of speaking practice designed to improve presentation skills. First-year high-school students repeatedly engaged in book-talk activities for a certain period of time. During the activities, they were given a speaking format to facilitate their performance. At the end of the instruction period, students’ speaking fluency was measured, analyzed, and compared with that of a control group. The comparative analysis demonstrates that the students’ fluency improves substantially when they are provided with a speaking format. The result supports the hypothesis that this format helps to lessen the students’ cognitive load at the initial conceptualization stage and instead helps to save cognitive resources for successive stages of speech production, which consequently enhances the students’ speaking performance

An antifungal compound involved in symbiotic germination of Cypripedium macranthos var. rebunense (Orchidaceae)

Germination of orchid seeds fully depends on a symbiotic association with soil-borne fungi, usually Rhizoctonia spp. In contrast to the peaceful symbiotic associations between many other terrestrial plants and mycorrhizal fungi, this association is a life-and-death struggle. The fungi always try to invade the cytoplasm of orchid cells to obtain nutritional compounds. On the other hand, the orchid cells restrict the growth of the infecting hyphae and obtain nutrition by digesting them. It is likely that antifungal compounds are involved in the restriction of fungal growth. Two antifungal compounds, lusianthrin and chrysin, were isolated from the seedlings of Cypripedium macranthos var. rebunense that had developed shoots. The former had a slightly stronger antifungal activity than the latter, and the antifungal spectra of these compounds were relatively specific to the nonpathogenic Rhizoctonia spp. The level of lusianthrin, which was very low in aseptic protocorm-like bodies, dramatically increased following infection with the symbiotic fungus. In contrast, chrysin was not detected in infected protocorm-like bodies. These results suggest that orchid plants equip multiple antifungal compounds and use them at specific developmental stages; lusianthrin maintains the perilous symbiotic association for germination and chrysin helps to protect adult plants

Elevated ozone disrupts the plant-insect communication; Changes of attractiveness of Japanese white birch leaves to Agelastica coerulea via Biogenic Volatile Organic Compounds (BVOCs)

Elevated ground-level ozone (O3) reduced C-based defense chemicals; however, severe grazing damages were found in leaves grown in the low O3 condition of a free air O3-concentration enrichment system. To explain this phenomenon, this study investigates the role of BVOCs (Biogenic Volatile Organic Compounds) as signaling compounds for insect herbivores. BVOCs act as scents for herbivore insects to locate host plants, while some BVOCs show high reactivity to O3, inducing changes in the composition of BVOCs in atmospheres with elevated O3. In this study, profiles of BVOCs emitted from birch (Betula platyphylla var. japonica) leaves were analyzed, and Y-tube insect preference tests were conducted to study the insect olfactory response. The assays were conducted in June and August or September, according to the life cycle of the adult alder leaf beetle Agelastica coerulea. The Y-tube tests revealed that the leaf beetles were attracted to BVOCs, and O3 per se had neither an attractant nor a repellent effect. BVOCs became less attractant when mixed with highly concentrated O3 (>80 ppb). About 20% of the total BVOCs emissions were highly O3-reactive compounds, such as β-ocimene. The results suggest that BVOCs emitted from the birch leaves can be altered by elevated O3, and, thus, potentially reducing the attractiveness of leaves to herbivorous insects searching for food