159 research outputs found
Development of a chlorophyll fluorescence imaging system for the quality assessment of fruits and vegetables
No full textChlorophyll fluorescence has been used for a long time as a powerful tool to
investigate the functioning of the photosynthetic apparatus of photosynthetic organisms. It is
an extremely sensitive technique, though such sensitivity often makes its results very difficult
to decipher. One of its main advantages is that it is a non-destructive technique, which makes
it ideally suited for fast screening of large collections of samples. Traditionally, chlorophyll
fluorescence is measured by specially designed fluorimeters, which perform point
measurements on the sample surface. In the last decade a new approach, chlorophyll
fluorescence imaging, has been developed in order to measure the distribution of chlorophyll
fluorescence emission in two dimensions. Research work in this area is still at an early stage,
and a few research groups developed different approaches to the problem.
The present thesis deals with the development of a chlorophyll fluorescence imaging
system carried out at the Laboratory of Botany of the Limburgs Universitair Centrum and its
application in the field of fruit quality assessment, in the study of plant heavy metal stress, on
the effects of disturbances of the endogenous phytohormone balance and as a diagnostic
method for pre-symptomatic detection of viral infections.
The system is composed of an excitation unit, an imaging unit and a control unit.
Chlorophyll fluorescence is detected by a CCD camera fitted with a red cut-off filter, upon
excitation with xenon lamps filtered with a solution of copper sulphate, which provides a blue
cut-off low-pass filter. A detailed description of the system is presented and relevant technical
issues are discussed. In particular, advantages and drawbacks implied by the technical
solutions adopted are addressed.
The mainstream application of the chlorophyll fluorescence imaging system is in the
field of apple quality assessment. After a description of the typical behavior of an apple in
terms of fluorescence emission as measured by the fluorescence imaging system, results from
various experiments with apple material are reported. The suitability of the technique as a
predictor for development of storage diseases is discussed on the basis of an example of
successful prediction. In experiments with apples grown with or without extra nitrogen
supply, the system proved to be able to detect differences in fluorescence emission related to the nitrogen treatment. New perspectives opened by such result are discussed. Progress made
in using advanced analysis tools like Artificial Neural Networks is also addressed. The system
was used also in an experiment with apples grown in orchards treated with different water
regimes. In this case, unfortunately, the system could not detect any remarkable differences
related to the irrigation regimes.
The fluorescence imaging systems, though designed with special attention to its
application in fruit quality control, can be applied also to other fields of research. A gallery of
three examples of an alternative application is presented. In particular, results are shown from
experiments made on heavy metal treated bean plants, on virus-inoculated Nicotiana
benthamiana and on cytokinin-overexpressing transgenic Pssu-ipt tobaccо.
Heavy metal treated plants showed a variation of fluorescence emission in time
during the metal treatment. Not only the intensity of fluorescence emission changed, but also
its distribution on the leaf, opening the way to speculations about the possible correlation of
the difference observed and the distribution of metal ions within the leaf.
The inoculation of Nicotiana benthamiana plants with pepper mild mottle virus
caused an alteration of the fluorescence emission pattern a few days after the inoculation in
otherwise asymptomatic leaves. A peculiar pattern could be observed, which might be related
to the spreading of the virus from the site of inoculation to other parts of the plant.
Transgenic Pssu-ipt tobacco, characterized by an elevated content of endogenous
cytokinin, also showed a peculiar pattern of fluorescence emission, with altered kinetics in
mesophyll areas at a distance from the main veins. Possible explanations of such phenomenon
are attempted.
In the appendices, the software tools used in this research work are presented. In
particular, a description is given of the following programs:
Grabix: Developed by the author, this is the software that controls the whole
fluorescence imaging system.
KhorosPro 2001, Student edition: This is a very flexible multi-purpose
software suite for image analysis, used to process fluorescence images after
being captured with Grabix.
R: This is the programming language for statistical data analysis used to
extract statistical information from the images. Stuttgart Neural Network Simulator (SNNS): It is the simulator used to
analyze fluorescence images by means of artificial neural networks
Development of a chlorophyll fluorescence imaging system for the quality assessment of fruits and vegetables
No full textChlorophyll fluorescence has been used for a long time as a powerful tool to
investigate the functioning of the photosynthetic apparatus of photosynthetic organisms. It is
an extremely sensitive technique, though such sensitivity often makes its results very difficult
to decipher. One of its main advantages is that it is a non-destructive technique, which makes
it ideally suited for fast screening of large collections of samples. Traditionally, chlorophyll
fluorescence is measured by specially designed fluorimeters, which perform point
measurements on the sample surface. In the last decade a new approach, chlorophyll
fluorescence imaging, has been developed in order to measure the distribution of chlorophyll
fluorescence emission in two dimensions. Research work in this area is still at an early stage,
and a few research groups developed different approaches to the problem.
The present thesis deals with the development of a chlorophyll fluorescence imaging
system carried out at the Laboratory of Botany of the Limburgs Universitair Centrum and its
application in the field of fruit quality assessment, in the study of plant heavy metal stress, on
the effects of disturbances of the endogenous phytohormone balance and as a diagnostic
method for pre-symptomatic detection of viral infections.
The system is composed of an excitation unit, an imaging unit and a control unit.
Chlorophyll fluorescence is detected by a CCD camera fitted with a red cut-off filter, upon
excitation with xenon lamps filtered with a solution of copper sulphate, which provides a blue
cut-off low-pass filter. A detailed description of the system is presented and relevant technical
issues are discussed. In particular, advantages and drawbacks implied by the technical
solutions adopted are addressed.
The mainstream application of the chlorophyll fluorescence imaging system is in the
field of apple quality assessment. After a description of the typical behavior of an apple in
terms of fluorescence emission as measured by the fluorescence imaging system, results from
various experiments with apple material are reported. The suitability of the technique as a
predictor for development of storage diseases is discussed on the basis of an example of
successful prediction. In experiments with apples grown with or without extra nitrogen
supply, the system proved to be able to detect differences in fluorescence emission related to the nitrogen treatment. New perspectives opened by such result are discussed. Progress made
in using advanced analysis tools like Artificial Neural Networks is also addressed. The system
was used also in an experiment with apples grown in orchards treated with different water
regimes. In this case, unfortunately, the system could not detect any remarkable differences
related to the irrigation regimes.
The fluorescence imaging systems, though designed with special attention to its
application in fruit quality control, can be applied also to other fields of research. A gallery of
three examples of an alternative application is presented. In particular, results are shown from
experiments made on heavy metal treated bean plants, on virus-inoculated Nicotiana
benthamiana and on cytokinin-overexpressing transgenic Pssu-ipt tobaccо.
Heavy metal treated plants showed a variation of fluorescence emission in time
during the metal treatment. Not only the intensity of fluorescence emission changed, but also
its distribution on the leaf, opening the way to speculations about the possible correlation of
the difference observed and the distribution of metal ions within the leaf.
The inoculation of Nicotiana benthamiana plants with pepper mild mottle virus
caused an alteration of the fluorescence emission pattern a few days after the inoculation in
otherwise asymptomatic leaves. A peculiar pattern could be observed, which might be related
to the spreading of the virus from the site of inoculation to other parts of the plant.
Transgenic Pssu-ipt tobacco, characterized by an elevated content of endogenous
cytokinin, also showed a peculiar pattern of fluorescence emission, with altered kinetics in
mesophyll areas at a distance from the main veins. Possible explanations of such phenomenon
are attempted.
In the appendices, the software tools used in this research work are presented. In
particular, a description is given of the following programs:
Grabix: Developed by the author, this is the software that controls the whole
fluorescence imaging system.
KhorosPro 2001, Student edition: This is a very flexible multi-purpose
software suite for image analysis, used to process fluorescence images after
being captured with Grabix.
R: This is the programming language for statistical data analysis used to
extract statistical information from the images. Stuttgart Neural Network Simulator (SNNS): It is the simulator used to
analyze fluorescence images by means of artificial neural networks
Back to the future: An experiment on ecological restoration
No full textThe urgency of climate, biodiversity, and pollution crises has prompted international and national institutions to move beyond the prevention and mitigation of damages and to design policies aimed at promoting ecological restoration. In this paper, we address this emerging policy challenge by presenting experimental evidence on individuals' propensity to contribute to restoration activities. Specifically, our design links a common pool resource game to a public good game to investigate how previous resource exploitation influences restoration decisions. We find that history matters since subjects who participate in resource depletion show a different behavior as compared to subjects who are only called to restore it. Specifically, while the former are subject to behavioral lock-ins that influence the success of restoration, the latter are more prompt to restore the more the resource is depleted
Anti-HMGCR myopathy misdiagnosed as motor neuron disease and complicated with COVID-19 infection
No full text
G. Ciscato — Sulle formole fondamentali della trigonometria sferoidica date da G.-H. Halphen (Extrait des Atti de l’Institut royal vénitien des Sciences, Lettres et Arts , t. III, série VII)
No full textG. Ciscato — Sulle formole fondamentali della trigonometria sferoidica date da G.-H. Halphen (Extrait des Atti de l’Institut royal vénitien des Sciences, Lettres et Arts , t. III, série VII). In: Bulletin astronomique, tome 10, 1893. p. 442
Back to the future: An experiment on ecological restoration
No full textThe urgency of climate, biodiversity, and pollution crises has prompted international and national institutions
to move beyond the prevention and mitigation of damages and to design policies aimed at promoting ecological
restoration. In this paper, we address this emerging policy challenge by presenting experimental evidence on
individuals’ propensity to contribute to restoration activities. Specifically, our design links a common pool
resource game to a public good game to investigate how previous resource exploitation influences restoration
decisions. We find that history matters since subjects who participate in resource depletion show a different
behavior as compared to subjects who are only called to restore it. Specifically, while the former are subject
to behavioral lock-ins that influence the success of restoration, the latter are more prompt to restore the more
the resource is depleted
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