title: H₂¹⁸O labelled vapour reveals evidence of radial Péclet effects in some leaves, but not all

authors: White, Melissa

subjects: Péclet

abstract: Previous studies demonstrated the importance of pathways of water movement, hydraulic conductance, and leaf hydraulic design on leaf water isotopic enrichment. The current study addresses the relevance of Péclet effects to leaf water isotopic enrichment by assessing spatial variation and comparing bulk leaf water enrichment to Craig-Gordon modelled values. Vapour isotope labelling was also utilised in an experimental first to quantify the carry-forward of mesophyll water isotope compositions to more distal parts of corn (Zea mays), oat (Avena sativa), sunflower (Helianthus annuus) and foxglove (Digitalis purpurea) leaves through coupled leaf gas exchange and isoflux measurements. In this study, we found that the Péclet effect was relevant to patterns of leaf water isotopic enrichment for three out of four species tested. The change in H₂¹⁸O for both monocots highlighted a vascular Péclet effect, while the change in foxglove showed a mesophyll Péclet effect, both of which were found to be relevant for the isotopic enrichment of transpired vapour and leaf water. In contrast, sunflower did not present any evidence of either a vascular or a mesophyll Péclet effect, suggesting a difference in leaf hydraulic design. These findings help us to understand how differences in leaf hydraulic design and anatomy influence the development of gradients in leaf water isotopes. This improved understanding will assist in the most appropriate choice of theoretical models to accurately predict leaf water isotope composition for applications as varied as predicting past climates from tree ring isotopes or selecting water-use efficient genotypes in crop plants.

text: H₂¹⁸O labelled vapour reveals evidence of radial Péclet effects in some leaves, but not all Previous studies demonstrated the importance of pathways of water movement, hydraulic conductance, and leaf hydraulic design on leaf water isotopic enrichment. The current study addresses the relevance of Péclet effects to leaf water isotopic enrichment by assessing spatial variation and comparing bulk leaf water enrichment to Craig-Gordon modelled values. Vapour isotope labelling was also utilised in an experimental first to quantify the carry-forward of mesophyll water isotope compositions to more distal parts of corn (Zea mays), oat (Avena sativa), sunflower (Helianthus annuus) and foxglove (Digitalis purpurea) leaves through coupled leaf gas exchange and isoflux measurements. In this study, we found that the Péclet effect was relevant to patterns of leaf water isotopic enrichment for three out of four species tested. The change in H₂¹⁸O for both monocots highlighted a vascular Péclet effect, while the change in foxglove showed a mesophyll Péclet effect, both of which were found to be relevant for the isotopic enrichment of transpired vapour and leaf water. In contrast, sunflower did not present any evidence of either a vascular or a mesophyll Péclet effect, suggesting a difference in leaf hydraulic design. These findings help us to understand how differences in leaf hydraulic design and anatomy influence the development of gradients in leaf water isotopes. This improved understanding will assist in the most appropriate choice of theoretical models to accurately predict leaf water isotope composition for applications as varied as predicting past climates from tree ring isotopes or selecting water-use efficient genotypes in crop plants.

year: 2022

title: Teaching and learning about matter in Grade 6 classrooms: a conceptual change approach

authors: Pimthong, Pattamaporn

subjects: conceptual change

abstract: The purpose of this study was to enhance the teaching and learning of matter and its properties for grade 6 students. The development of a conceptual change approach instructional unit was undertaken for this purpose. Pre- and post-concept surveys, classroom observations, and student and teacher interviews were used to collect data. The teaching activities not only challenged and encouraged students’ conceptual change but also indicated that teachers needed to develop their content knowledge and teaching strategies. The participants developed more scientific conceptions and were able to apply these in appropriate contexts. This study illustrates how a conceptual change approach can be accomplished in the Thai context.

text: Teaching and learning about matter in Grade 6 classrooms: a conceptual change approach The purpose of this study was to enhance the teaching and learning of matter and its properties for grade 6 students. The development of a conceptual change approach instructional unit was undertaken for this purpose. Pre- and post-concept surveys, classroom observations, and student and teacher interviews were used to collect data. The teaching activities not only challenged and encouraged students’ conceptual change but also indicated that teachers needed to develop their content knowledge and teaching strategies. The participants developed more scientific conceptions and were able to apply these in appropriate contexts. This study illustrates how a conceptual change approach can be accomplished in the Thai context.

year: 2011

title: Maori and psychology: Research and practice (full conference proceedings)

authors: Robertson, Neville

subjects: Maori

abstract: This is the full proceedings of the symposium sponsored by the Maori and Psychology Research Unit at the University of Waikato: Maori and psychology: Research and practice. The publication of the proceedings of this symposium marks a significant milestone for the Maori and Psychology Research Unit (MPRU). Since its inception in 1997, the unit has played an important role in nurturing and supporting students to engage in Maori-focussed research. They have played, and continue to play, an important part in our research activities as interviewers, analysts, coordinators and writers. 
The MPRU symposium was organised to serve as a platform to profile the work of our students, to disseminate research results and to invite other researchers to witness the nature of the MPRU’s work.

text: Maori and psychology: Research and practice (full conference proceedings) This is the full proceedings of the symposium sponsored by the Maori and Psychology Research Unit at the University of Waikato: Maori and psychology: Research and practice. The publication of the proceedings of this symposium marks a significant milestone for the Maori and Psychology Research Unit (MPRU). Since its inception in 1997, the unit has played an important role in nurturing and supporting students to engage in Maori-focussed research. They have played, and continue to play, an important part in our research activities as interviewers, analysts, coordinators and writers. 
The MPRU symposium was organised to serve as a platform to profile the work of our students, to disseminate research results and to invite other researchers to witness the nature of the MPRU’s work.

year: 1999