title: On the gas exchange and isofluxes of New Zealand mosses

authors: Ng, Tania Zi Xin

subjects: Moss

abstract: The stable isotopic composition of plant tissue reflects the biophysical and biochemical processes that occur during water uptake and cellulose synthesis. Stable isotope techniques in plant science have primarily focused on vascular plants; however, there is a growing interest in the stable isotopic composition of nonvascular plants, especially for paleoclimate reconstruction. The stable carbon isotopic composition of plant organic matter provides information of when a plant was photosynthetically active, while the stable oxygen isotopic composition can infer the environmental conditions that favoured photosynthesis. Presently, little is known about the relationship between the stable oxygen isotopic composition of moss tissue and the environment due to the complexity of the isotopic fractionation processes involved. This thesis offers insight on the oxygen isotopic composition of moss tissue and phyllid water through three separate studies and addresses the possible isotopic fractionation processes that may influence the stable isotopic composition observed.

The first study investigated the oxygen isotopic composition of evaporated water from two species of moss: Ptychomnion aciculare and Dawsonia superba. Measurements of on-line gas exchange and the isotopic composition of vapour water from the mosses were taken. Two oxygen isotope theories were applied to explain the observed oxygen isotopic composition of evaporated water. The first isotope theory was Rayleigh’s distillation theory, often used to describe the oxygen isotope variation observed in the global hydrological cycle. The second theory was the modified Craig–Gordon model, often applied to isotopic enrichment in vascular leaves. The results highlighted how the anatomical differences of the phyllid structure influences the isotopic composition of evaporated and transpired water.

The second study interpreted the stable carbon and oxygen isotopic composition of D. superba stems. This involved taking 10 mm transverse sections along the stem and analyzing the isotopic composition of each section. The results from the carbon isotope analysis indicated that the carbon isotopic composition was more depleted at the base of stem compared to the tip, suggesting soil respiration, rather than atmospheric CO₂, was the primary factor influencing the isotopic composition of the stem. Additionally, analyses of the stable oxygen isotopic composition of D. superba stem indicated seasonal variations that coincided with the seasonal shifts in the oxygen stable isotopic composition of precipitation.

The final study investigated the relationship between the isotopic composition of Sphagnum cuspidatum bulk tissue and the oxygen isotopic composition of source water was investigated under laboratory settings. The oxygen isotopic composition of moss tissue is theorized to reflect the oxygen isotopic composition of source water, offset by the biochemical fractionation constant. Four sealed growth chambers were set up and the mosses were watered with different isotopically labelled water for 6 months. S. cuspidatum was harvested, dried, and analyzed for the stable isotopic composition. The results indicated that oxygen isotopic composition of moss tissue increased by 0.17‰ for every 1‰ increase in source water, a relationship much lower than predicted by the theory. This suggested that the isotopic composition of moss tissue reflects an equilibrium process between source water and the vapour from atmospheric air.

These studies contribute theoretical and practical advancements in understanding the relationship between moss stable isotopes and the environment. The research here demonstrated the relationship between the oxygen isotopic composition of moss bulk tissue to the oxygen isotopic composition of precipitation and water sources, in both field and laboratory settings. They also provide insight into how the physiology and anatomy of moss phyllids influence the observed isotopic composition fixed in organic material.

text: On the gas exchange and isofluxes of New Zealand mosses The stable isotopic composition of plant tissue reflects the biophysical and biochemical processes that occur during water uptake and cellulose synthesis. Stable isotope techniques in plant science have primarily focused on vascular plants; however, there is a growing interest in the stable isotopic composition of nonvascular plants, especially for paleoclimate reconstruction. The stable carbon isotopic composition of plant organic matter provides information of when a plant was photosynthetically active, while the stable oxygen isotopic composition can infer the environmental conditions that favoured photosynthesis. Presently, little is known about the relationship between the stable oxygen isotopic composition of moss tissue and the environment due to the complexity of the isotopic fractionation processes involved. This thesis offers insight on the oxygen isotopic composition of moss tissue and phyllid water through three separate studies and addresses the possible isotopic fractionation processes that may influence the stable isotopic composition observed.

The first study investigated the oxygen isotopic composition of evaporated water from two species of moss: Ptychomnion aciculare and Dawsonia superba. Measurements of on-line gas exchange and the isotopic composition of vapour water from the mosses were taken. Two oxygen isotope theories were applied to explain the observed oxygen isotopic composition of evaporated water. The first isotope theory was Rayleigh’s distillation theory, often used to describe the oxygen isotope variation observed in the global hydrological cycle. The second theory was the modified Craig–Gordon model, often applied to isotopic enrichment in vascular leaves. The results highlighted how the anatomical differences of the phyllid structure influences the isotopic composition of evaporated and transpired water.

The second study interpreted the stable carbon and oxygen isotopic composition of D. superba stems. This involved taking 10 mm transverse sections along the stem and analyzing the isotopic composition of each section. The results from the carbon isotope analysis indicated that the carbon isotopic composition was more depleted at the base of stem compared to the tip, suggesting soil respiration, rather than atmospheric CO₂, was the primary factor influencing the isotopic composition of the stem. Additionally, analyses of the stable oxygen isotopic composition of D. superba stem indicated seasonal variations that coincided with the seasonal shifts in the oxygen stable isotopic composition of precipitation.

The final study investigated the relationship between the isotopic composition of Sphagnum cuspidatum bulk tissue and the oxygen isotopic composition of source water was investigated under laboratory settings. The oxygen isotopic composition of moss tissue is theorized to reflect the oxygen isotopic composition of source water, offset by the biochemical fractionation constant. Four sealed growth chambers were set up and the mosses were watered with different isotopically labelled water for 6 months. S. cuspidatum was harvested, dried, and analyzed for the stable isotopic composition. The results indicated that oxygen isotopic composition of moss tissue increased by 0.17‰ for every 1‰ increase in source water, a relationship much lower than predicted by the theory. This suggested that the isotopic composition of moss tissue reflects an equilibrium process between source water and the vapour from atmospheric air.

These studies contribute theoretical and practical advancements in understanding the relationship between moss stable isotopes and the environment. The research here demonstrated the relationship between the oxygen isotopic composition of moss bulk tissue to the oxygen isotopic composition of precipitation and water sources, in both field and laboratory settings. They also provide insight into how the physiology and anatomy of moss phyllids influence the observed isotopic composition fixed in organic material.

year: 2023

title: Investigating aquaphotomics for fruit quality assessment

authors: Kaur, Harpreet

subjects: Fruit quality

abstract: The methods of aquaphotomics were explored for internal fruit quality assessment, such as dry matter (DM) and soluble solid content (SSC) measurement using near infrared spectroscopy (NIRS). Fruits like apple and kiwifruit are more than 80% water. The NIR spectrum of whole intact fruit is dominated by water absorption peaks that shift and vary in shape with changes in quantities such as SSC, DM, and temperature. These variations can significantly reduce predictive model performance for fruit quality parameters.  Because the absorption peak at 1450 nm (first overtone of the OH stretch of water) and 970 nm (second overtone of the OH stretch of water) in the samples varies with SSC, DM concentration, and temperature, an investigation was undertaken on the aquaphotomics approach to quantify changes in the water structure that are apparent in the two wavelength regions.
The key question examined was whether aquaphotomics can help in the development of better and simpler prediction models or hardware for intact fruit quality measurements beneficial to the industry. To find answers to this question, several experiments were conducted. Much work in aquaphotomics has been done in the longer wavelength region, that is, at the first overtone (1300–1600 nm), which requires short pathlength cells due to higher water absorption. Experiments were performed on simple aqueous systems such as sucrose solution of various concentrations and an aqueous system such as apple and kiwifruit juice. The second overtone wavelength region (800‒1100 nm) was also scrutinized for fruit juice measurements using a long pathlength cell. Eventually, experiments were conducted on whole intact fruit.
A Fourier transform near infrared (FT-NIR) spectrophotometer was used to acquire spectra of aqueous samples over the wavelength range of 900 to 1800 nm. For whole, intact fruit spectra collection, spectrophotometers in the wavelength range below 1100 nm were utilized. An in-house benchtop spectrometer based on the Zeiss MMS-1 NIR spectrometer operated in interactance mode was used along with some commercially available handheld spectrophotometers such as the F-750 produce quality spectrometer and the SCiO spectrometer. The spectra acquired with the instruments were analyzed using multivariate data analysis. The calibration models were developed using partial least square regression (PLSR) and multiple linear regression to estimate quality attributes.
The NIR spectrum of fruit is affected by temperature. Therefore, a calibration equation developed at one fixed temperature cannot reliably predict samples at a different temperature. Using the framework of aquaphotomics, the changes within the water structure of fruit juice and whole intact fruit occurring with changes in temperature were analysed. Water wavelengths affected by temperature variation were identified in the first and second overtone regions. Using aquagrams, it appeared that different water species were activated in the first and second overtone region. The influence of increasing temperature on the peak absorbance of the juice was a lateral shift in the first overtone region, whereas it was vertical in the second overtone region of water. Two correction pre-treatments; extended multiplicative scatter correction (EMSC) and external parameter orthogonalization (EPO) were used in conjunction with principal component loading of water as an interferent spectrum. They were able to correct for temperature effects by at least a factor of 10 to insignificant levels.
It was concluded that the aquaphotomics paradigm offers fundamental insights into the role of the various light absorption mechanisms but only in conjunction with chemometrics tools, like EMSC and EPO, leading to an improvement in predictive model performance. The investigated methods have good potential to be used for quality assessment of fruit in industry.

text: Investigating aquaphotomics for fruit quality assessment The methods of aquaphotomics were explored for internal fruit quality assessment, such as dry matter (DM) and soluble solid content (SSC) measurement using near infrared spectroscopy (NIRS). Fruits like apple and kiwifruit are more than 80% water. The NIR spectrum of whole intact fruit is dominated by water absorption peaks that shift and vary in shape with changes in quantities such as SSC, DM, and temperature. These variations can significantly reduce predictive model performance for fruit quality parameters.  Because the absorption peak at 1450 nm (first overtone of the OH stretch of water) and 970 nm (second overtone of the OH stretch of water) in the samples varies with SSC, DM concentration, and temperature, an investigation was undertaken on the aquaphotomics approach to quantify changes in the water structure that are apparent in the two wavelength regions.
The key question examined was whether aquaphotomics can help in the development of better and simpler prediction models or hardware for intact fruit quality measurements beneficial to the industry. To find answers to this question, several experiments were conducted. Much work in aquaphotomics has been done in the longer wavelength region, that is, at the first overtone (1300–1600 nm), which requires short pathlength cells due to higher water absorption. Experiments were performed on simple aqueous systems such as sucrose solution of various concentrations and an aqueous system such as apple and kiwifruit juice. The second overtone wavelength region (800‒1100 nm) was also scrutinized for fruit juice measurements using a long pathlength cell. Eventually, experiments were conducted on whole intact fruit.
A Fourier transform near infrared (FT-NIR) spectrophotometer was used to acquire spectra of aqueous samples over the wavelength range of 900 to 1800 nm. For whole, intact fruit spectra collection, spectrophotometers in the wavelength range below 1100 nm were utilized. An in-house benchtop spectrometer based on the Zeiss MMS-1 NIR spectrometer operated in interactance mode was used along with some commercially available handheld spectrophotometers such as the F-750 produce quality spectrometer and the SCiO spectrometer. The spectra acquired with the instruments were analyzed using multivariate data analysis. The calibration models were developed using partial least square regression (PLSR) and multiple linear regression to estimate quality attributes.
The NIR spectrum of fruit is affected by temperature. Therefore, a calibration equation developed at one fixed temperature cannot reliably predict samples at a different temperature. Using the framework of aquaphotomics, the changes within the water structure of fruit juice and whole intact fruit occurring with changes in temperature were analysed. Water wavelengths affected by temperature variation were identified in the first and second overtone regions. Using aquagrams, it appeared that different water species were activated in the first and second overtone region. The influence of increasing temperature on the peak absorbance of the juice was a lateral shift in the first overtone region, whereas it was vertical in the second overtone region of water. Two correction pre-treatments; extended multiplicative scatter correction (EMSC) and external parameter orthogonalization (EPO) were used in conjunction with principal component loading of water as an interferent spectrum. They were able to correct for temperature effects by at least a factor of 10 to insignificant levels.
It was concluded that the aquaphotomics paradigm offers fundamental insights into the role of the various light absorption mechanisms but only in conjunction with chemometrics tools, like EMSC and EPO, leading to an improvement in predictive model performance. The investigated methods have good potential to be used for quality assessment of fruit in industry.

year: 2020

title: Engaging and working with Maori? Effective practice for psychologists in education

authors: Glynn, Ted

subjects: New Zealand

abstract: I believe this whakatauki captures the reflective processes I am now engaged in, as I assess where I have come from and where I am going, as a second-generation pakeha of Irish descent, who completed postgraduate degrees in Psychology and Education in New Zealand and Canada, and who has been engaging and working with Māori in the field of education for many years.

text: Engaging and working with Maori? Effective practice for psychologists in education I believe this whakatauki captures the reflective processes I am now engaged in, as I assess where I have come from and where I am going, as a second-generation pakeha of Irish descent, who completed postgraduate degrees in Psychology and Education in New Zealand and Canada, and who has been engaging and working with Māori in the field of education for many years.

year: 2008