First report of the ectomycorrhizal status of boletes on the Northern Yucatan Peninsula, Mexico determined using isotopic methods

Despite their prominent role for tree growth, few studies have examined the occurrence of ectomycorrhizal fungi in lowland, seasonally dry tropical forests (SDTF). Although fruiting bodies of boletes have been observed in a dry tropical forest on the Northern Yucatan Peninsula, Mexico, their occurrence is rare and their mycorrhizal status is uncertain. To determine the trophic status (mycorrhizal vs. saprotrophic) of these boletes, fruiting bodies were collected and isotopically compared to known saprotrophic fungi, foliage, and soil from the same site. Mean δ15N and δ13C values differed significantly between boletes and saprotrophic fungi, with boletes 8.0‰ enriched and 2.5‰ depleted in 15N and 13C, respectively relative to saprotrophic fungi. Foliage was depleted in 13C relative to both boletes and saprotrophic fungi. Foliar δ15N values, on the other hand, were similar to saprotrophic fungi, yet were considerably lower relative to bolete fruiting bodies. Results from this study provide the first isotopic evidence of ectomycorrhizal fungi in lowland SDTF and emphasize the need for further research to better understand the diversity and ecological importance of ectomycorrhizal fungi in these forested ecosystems

Natuurkunde en scheikunde practica in het nieuwe curriculum:leren onderzoeken of niet?

Dat leerlingen onderzoeksvaardigheden opdoen is in de nieuwe èxamenprogramma’s voor natuurkunde en scheikunde in het VO belangrijker geworden. Schoolpractica zijn vaak ‘kookboek’ achtig en daarmee niet geschikt om onderzoeksvaardigheden mee op te doen. De onderzoekers analyseerden de door lesmethoden aangeboden practica voor natuurkunde en scheikunde van zowel de oude als de nieuwe uitgaven op het doel van de practica: begripsverankering, apparatuur leren gebruiken of onderzoeksvaardigheden. Ook is de leerlingsturing in deze practica geanalyseerd: wat ligt vast; maken leerlingen eigen keuzes? Resultaten tonen dat nieuwe lesmethoden in de practica minder nadruk leggen op onderzoeksvaardigheden aanleren dan die behorende bij het vorige examenprogramma. Het onderzoek levert aanknopingspunten op over docentactiviteiten die helpen leerlingen aan de exameneis over onderzoeksvaardigheden te kunnen laten voldoen

Superhelden in de klas:Waar hoort Vibranium in het Periodiek Systeem?

Fictieve stoffen spelen regelmatig een belangrijke rol in superhelden strips en films. Superman verliest bijvoorbeeld zijn superkracht wanneer hij in aanraking komt met de stof kryptoniet. In de recente film Black Panther komt het metaal vibranium voor. In dit artikel beschrijven we een motiverende opdracht waarin met behulp van vibranium de chemische kennis van 6-vwo-leerlingen geactiveerd wordt

Analysing the physics learning environment of visually impaired students in high schools

Although visually impaired students attend regular high school, their enrolment in advanced science classes is dramatically low. In our research we evaluated the physics learning environment of a blind high school student in a regular Dutch high school. For visually impaired students to grasp physics concepts, time and additional materials to support the learning process are key. Time for teachers to develop teaching methods for such students is scarce. Suggestions for changes to the learning environment and of materials used are given. Although visually impaired students attend regular high school, their enrolment in advanced science classes is dramatically low. In our research we evaluated the physics learning environment of a blind high school student in a regular Dutch high school. For visually impaired students to grasp physics concepts, time and additional materials to support the learning process are key. Time for teachers to develop teaching methods for such students is scarce. Suggestions for changes to the learning environment and of materials used are given

Improving physics teaching materials on sound for visually impaired students in high school

\u3cp\u3eWhen visually impaired students attend regular high school, additional materials are necessary to help them understand physics concepts. The time for teachers to develop teaching materials for such students is scarce. Visually impaired students in regular high school physics classes often use a braille version of the physics textbook. Previously, we evaluated the physics learning environment of a blind high school student in a regular Dutch high school. In this research we evaluate the use of a revised braille textbook, relief drawings and 3D models. The research focussed on the topic of sound in grade 10.\u3c/p\u3

Preliminary studies of micropropagation of Hopea odorata, a dipterocarp tree

Plantlet development from in vitro cultures of Hopea odorato Roxb. is described. Embryos excised from seeds and cultured on Gamborg's B5 or modified Murashige and Skoog (MS) medium with benzyladenine (BA, 2.2–22.2 μM) produced axillary shoots at cotyledonary and/or stem nodes. Shoot production was greatest in germinated embryos on modified MS medium with 8.9 μM BA. Excised axillary shoots formed few buds when cultured on medium with BA and limited root development occurred on Woody Plant Medium with naphthaleneacetic acid. Nodal explants from aseptically grown plantlets sprouted axillary shoots in modified MS medium with BA.E.S. Scott, A.N. Rao & C.S. Lo