Extensive production and wide application of TiO₂ nanoparticles has stimulated research on its potential biological effects on different groups of organisms but the interaction of TiO₂ nanoparticles ...with higher plants remains poorly understood. We have studied the effect of TiO₂ nanoparticles on Allium cepa using a modification of the conventional Allium test with nanoparticles suspended in distilled water as opposed to growth medium. Nanoparticulate TiO₂ was found to have low toxic potential and the mitotic index was among the most sensitive measures of the effect of nano-TiO₂. We conclude that modified Allium test is suitable to provide comparative data on the biological potential of a variety of nanoparticles and could be used in a tiered approach to nanotoxicity testing.
Use of a modified Allium test with nanoTiO2 KLANCNIK, K; DROBNE, D; VALANT, J ...
Ecotoxicology and environmental safety,
2011, 2011-Jan, 2011-01-00, 20110101, Volume:
74, Issue:
1
Journal Article
Peer reviewed
Extensive production and wide application of TiO(2) nanoparticles has stimulated research on its potential biological effects on different groups of organisms but the interaction of TiO(2) ...nanoparticles with higher plants remains poorly understood. We have studied the effect of TiO(2) nanoparticles on Allium cepa using a modification of the conventional Allium test with nanoparticles suspended in distilled water as opposed to growth medium. Nanoparticulate TiO(2) was found to have low toxic potential and the mitotic index was among the most sensitive measures of the effect of nano-TiO(2). We conclude that modified Allium test is suitable to provide comparative data on the biological potential of a variety of nanoparticles and could be used in a tiered approach to nanotoxicity testing.
The mechanisms of plant defence against cadmium toxicity have been studied by short-term exposure of
Lemna minor L. (common duckweed) to concentrations of CdCl
2 ranging from 0 to 500
μM. High ...accumulation of cadmium was observed (12,320
±
2155
μg
g
−1 at 500
μM CdCl
2), which caused a gradual decrease of plant growth, increased lipid peroxidation, and weakened the entire antioxidative defence. Total glutathione concentration decreased significantly; however, the concentration of oxidized glutathione remained stable. The responses of four antioxidant enzymes showed that catalase was the most inhibited after CdCl
2 exposure, ascorbate peroxidase and guaiacol peroxidase moderately, and glutathione reductase least. The total antioxidative potential revealed an induced antioxidative network at 0.1
μM CdCl
2 (137
±
13.2% of the control) and its reduction to only 47.4
±
4.0% of the control at higher cadmium concentrations. The possible application of the examined biomarkers in ecotoxicological research is discussed.
The increase of total antioxidative potential at low cadmium concentration is one of the mechanisms that helps duckweed to cope with cadmium-induced oxidative stress.
Elevated concentrations of copper in the environment result in accumulation of the metal in plants and cause an increase in reactive oxidative species (ROS). The first response to elevated amounts of ...ROS is increased levels of enzymatic and non-enzymatic antioxidants that reduce oxidative stress. The aim of our study was to evaluate the early stages of antioxidative responses to the low copper concentrations usually present in moderately polluted environments. In addition, some other parameters were examined to evaluate the effect of copper on plants.
Duckweed (Lemna minor L.) was exposed to different concentrations of copper sulphate for up to 24 hours. Glutathione concentration and enzymatic activities of catalase, guaiacol peroxidase and glutathione reductase were measured spectrophotometrically. Additionally, delayed and prompt chlorophyll fluorescence was measured by luminometry and fluorometry, respectively. The accumulation of copper in plants exposed for 24 hours to various concentrations of copper sulphate was measured by flame atomic absorption spectrophotometry.
The treatment of plants with copper sulphate resulted in an immediate decrease of the glutathione pool, which was replenished after 24 hours at CuSO4 concentrations lower than 2 microM. Higher CuSO4 concentrations caused a decrease of reduced glutathione. The responses of the antioxidant enzymes glutathione reductase, guaiacol peroxidase and catalase to CuSO4 differed during the first six hours of exposure, but their enzyme activities all increased after 24 hours of exposure. All these enzymes displayed biphasic activity curves with maximum values between 0.5 microM and 1 microM CuSO4. The response of guaiacol peroxidase was the most pronounced and statistically significantly specific and that of catalase the least. Delayed chlorophyll fluorescence decreased after exposure to 1 microM CuSO4, but no significant effect on maximum quantum yield of photosystem II (Fv/Fm) was observed. L. minor accumulated relatively high concentrations of copper. The accumulation rate was higher at lower concentrations of copper in the test medium (up to 2 microM CuSO4) than at concentrations above 2 microM CuSO4.
One of the most pronounced antioxidative responses to copper exposure was modified levels of oxidized and reduced forms of glutathione. The decrease of the glutathione pool is most probably coupled with induced production of phytochelatins. Antioxidative enzymes showed the biphasic enzyme activity characteristic of stress response. Guaiacol peroxidase exhibited the greatest significant increase of activity, even at higher CuSO4 concentrations at which the activity of catalase and glutathione reductase dropped. The intensity of delayed chlorophyll fluorescence decreased, indicating reduced photosynthesis of plants under stress. All the measured parameters showed that plants respond to even low copper concentrations very soon after exposure. The accumulation rate of copper in duckweed tissues indicates that L. minor is an accumulator species.
The synchronized and prompt inducibility of antioxidants indicates their involvement in a general plant defence strategy for coping with metal-induced oxidative stress. Glutathione concentration and guaiacol peroxidase activity were found to be the most sensitive of the early indicators of exposure to copper concentrations present in polluted water bodies.
The experimental design of the present study allowed us to compare the sensitivity of various methods and parameters for detecting plant responses to heavy metal-induced oxidative stress. The level of glutathione and the enzyme activities of guaiacol peroxidase and glutathione reductase could be used as a rapidly determined early warning system in toxicity studies.
Extensive production and wide application of TiO
2 nanoparticles has stimulated research on its potential biological effects on different groups of organisms but the interaction of TiO
2 ...nanoparticles with higher plants remains poorly understood. We have studied the effect of TiO
2 nanoparticles on
Allium cepa using a modification of the conventional
Allium test with nanoparticles suspended in distilled water as opposed to growth medium. Nanoparticulate TiO
2 was found to have low toxic potential and the mitotic index was among the most sensitive measures of the effect of nano-TiO
2. We conclude that modified
Allium test is suitable to provide comparative data on the biological potential of a variety of nanoparticles and could be used in a tiered approach to nanotoxicity testing.
Genome size (C-value) was measured in four species of Adriatic seagrasses with interphase-peak DNA image cytometry. The estimated 2C-value was 1.5
pg DNA for
Zostera noltii (2
n=12), 1.2
pg for
...Zostera marina (2
n=12), 1.1
pg for
Cymodocea nodosa (2
n=28) and 6.2
pg for
Posidonia oceanica, using
Pisum sativum (2C-value=8.84
pg) as the calibration standard. Seagrass leaves were fixed in 4% buffered formaldehyde to mitigate stoichiometric error due to tannins and post-fixed in 3:1 methanol:acetic acid (MAA). DNA was stained with the Feulgen reaction after hydrolysis in 5
M HCl for 90
min at 20
°C. Comparison of genome size of seagrasses with the data for other species of Alismatidae indicated that the ancestral genome of Alismatidae was relatively small.
The amount of nuclear DNA, expressed as the
C-value, was estimated for 13 marine halophytic plant species from six families. Plant material was collected in the nature reserve of the Strunjan saltpan ...in the Northern Adriatic and comprised all halophytic species inside the investigated area. Reproductive region of the shoot or root tips of halophytes were dissected, nuclei were Feulgen stained and 2
C-values were measured by DNA image cytometry as follows:
Crithmum maritimum (4.38
pg
DNA),
Artemisia caerulescens (6.43
pg),
Aster tripolium (21.43
pg),
Inula crithmoides (3.63
pg),
Atriplex portulacoides (1.83
pg),
A. prostrata (1.51
pg),
Salicornia europaea (2.75
pg),
Salsola soda (2.62
pg),
Sarcocornia fruticosa (5.91
pg),
Suaeda maritima (2.11
pg),
Limonium angustifolium (5.06
pg),
Puccinellia palustris (8.15
pg) and
Ruppia cirrhosa (4.65
pg). With the exception of the
C-value estimate for
A. caerulescens, which has been listed in the Plant DNA
C-values Database, the
C-values represent the first estimates for all the examined species. In addition, the
C-value for
R. cirrhosa is also the first report for the family Ruppiaceae. The investigated halophytes had a smaller genome size compared to other known
C-values for species within a particular family and also when compared to the mean values of dicots and monocots. The study also showed that halophylic annuals have a smaller genome size (2.49
pg) than perennial ones (7.45
pg
DNA).
To test the reliability of DNA image cytometry for the measurement of nuclear DNA content in plant material, we conducted independent experiments in two laboratories using different image analysis ...instruments for densitometric measurement of nuclear DNA amount in Feulgen-stained squash preparations of root tips. The 2C nuclear DNA content of the nine species studied spanned a 100-fold range (approx. 0.3–33pg). The estimates of nuclear DNA content measured with image cytometry methods were comparable to values obtained previously using both photometric cytometry and flow cytometry. Image cytometry methods showed little variation among repeated experiments within each laboratory or among different operators using the same instrument. Furthermore, the interphase-peak method (measurement of several hundred interphase nuclei per slide) was comparable to the classical prophase/telophase approach (measurement of ten early prophase and ten late telophase nuclei per slide). Hence, DNA image cytometry gives accurate and reproducible results and may be used as an alternative to photometric cytometry in plant nuclear DNA content measurements. In the present study, we propose that two standards for quality control of nuclear DNA content measurement are used in plant DNA image cytometry: (1) the coefficient of variation of the peak should be lower than 6%, and (2) the 4C/2C ratio should be between 1.9 and 2.1.
Polyploidisation, agmatoploidy and symploidy have driven the diversification of
sect.
. Several morphologically very similar species with different karyotypes have evolved, but their evolutionary ...origins and relationships are unknown. In this study, we used a combination of relative genome size and karyotype estimations as well amplified fragment length polymorphism (AFLP) fingerprinting to investigate the relationships among predominately (sub)alpine
,
and
in the Eastern Alps, including also some samples of
and
as outgroup. Our study revealed common co-occurrence of two or three different ploidies (di-, tetra- and hexaploids) at the same localities, and thus also common co-occurrence of different species, of which
was morphologically, ecologically and genetically most divergent. Whereas agmatoploid
likely originated only once from the Balkan
, and hexaploid
once from tetraploid
, the AFLP data suggest multiple origins of tetraploid
, from which partly agmatoploid individuals of
likely originated recurrently by partial fragmentation of the chromosomes. In contrast to common recurrent formation of polyploids in flowering plants, populations of agmatoploids resulting by fission of complete chromosome sets appear to have single origins, whereas partial agmatoploids are formed recurrently. Whether this is a general pattern in
sect.
and whether segregation of ecological niches supports the frequent co-occurrence of closely related cytotypes in mixed populations, remains the subject of ongoing research.
Polyploidisation, agmatoploidy and symploidy have driven the diversification of Luzula sect. Luzula. Several morphologically very similar species with different karyotypes have evolved, but their ...evolutionary origins and relationships are unknown. In this study, we used a combination of relative genome size and karyotype estimations as well amplified fragment length polymorphism (AFLP) fingerprinting to investigate the relationships among predominately (sub)alpine Luzula alpina, L. exspectata, L multiflora and L. sudetica in the Eastern Alps, including also some samples of L. campestris and L. taurica as outgroup. Our study revealed common co-occurrence of two or three different ploidies (di-, tetra- and hexaploids) at the same localities, and thus also common co-occurrence of different species, of which L. sudetica was morphologically, ecologically and genetically most divergent. Whereas agmatoploid L. exspectata likely originated only once from the Balkan L. taurica, and hexaploid L. multiflora once from tetraploid L. multiflora, the AFLP data suggest multiple origins of tetraploid L. multiflora, from which partly agmatoploid individuals of L. alpina likely originated recurrently by partial fragmentation of the chromosomes. In contrast to common recurrent formation of polyploids in flowering plants, populations of agmatoploids resulting by fission of complete chromosome sets appear to have single origins, whereas partial agmatoploids are formed recurrently. Whether this is a general pattern in Luzula sect. Luzula, and whether segregation of ecological niches supports the frequent co-occurrence of closely related cytotypes in mixed populations, remains the subject of ongoing research.
PDF
