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1.
In true leaves of common bean ( Phaseolus vulgaris L., cv. Berbukskaya) 11-day-old seedlings, pretreatment with 1.6 mM chlorocholine chloride (CCC) resulted in the improved
photosystem II (PSII) tolerance to UV-B radiation, an increase in the contents of cytokinins, ABA, and H 2O 2, but a decrease in the content of gibberellins. It is suggested that development of increased PSII tolerance to UV-B under
the influence of CCC is partially related to the increase in the contents of ABA, cytokinins, and UV-absorbing pigments in
the leaves of pretreated plants. 相似文献
2.
Mutations were induced in tissue-cultured wasabi ( Wasabia japonica Matsumura) by treating in vitro-derived shoot tips with either γ-rays or X-rays at 0, 10, 20, 40 or 80 Gy. Doses of up to 40 Gy of either γ- or X-ray treatments
resulted in a survival rate of more than 60% in culture after 3 mo. The use of γ- or X-rays at doses between 10 Gy and 40 Gy
to induce mutation in W. japonica resulted in an alteration of the growth and allyl isothiocyanate (AITC) content of multiple shoots after 3 mo. in culture
on Murashige and Skoog medium containing 5 μM N 6-benzyladenine (BA). Putative mutants from the 40 Gy treatments of either γ- or X-rays exhibited a reduction in shoot weight,
number, and height, whereas treatments of either γ-rays or X-rays at 10 Gy and 20 Gy doses showed no significant differences
in shoot growth. All shoots treated with 80 Gy were either necrotic or irregenerable, while those treated with 40 Gy produced
deformed leaves, from both types of ionizing radiation. Concentrations of AITC were measured by the use of gas chromatography-mass
spectrometry (GC-MS). The accumulation of AITC was shown to decrease when doses increased in both γ- and X-ray treatments,
compared with the controls. Positive responses were solely occurred at 18 mo. after transfer of in vitro rooted shoots to the shade house. The survival rate, rhizome weight and AITC content of plants derived from shoots treated
with 20 Gy or 40 Gy of either γ-rays or X-rays were significantly greater than those of the controls. 相似文献
3.
Arabidopsis thaliana grown in a light regime that included ultraviolet-B (UV-B) radiation (6 kJ m −2 d −1) had similar light-saturated photosynthetic rates but up to 50% lower stomatal conductance rates, as compared to plants grown
without UV-B radiation. Growth responses of Arabidopsis to UV-B radiation included lower leaf area (25%) and biomass (10%)
and higher UV-B absorbing compounds (30%) and chlorophyll content (52%). Lower stomatal conductance rates for plants grown
with UV-B radiation were, in part, due to lower stomatal density on the adaxial surface. Plants grown with UV-B radiation
had more capacity to down regulate photochemical efficiency of photosystem II (PSII) as shown by up to 25% lower φ PSII and 30% higher non-photochemical quenching of chlorophyll fluorescence under saturating light. These contributed to a smaller
reduction in the maximum photochemical efficiency of PSII ( F
v/ F
m), greater dark-recovery of F
v/ F
m, and higher light-saturated carbon assimilation and stomatal conductance and transpiration rates after a four-hour high light
treatment for plants grown with UV-B radiation. Plants grown with UV-B were more tolerant to a 12 day drought treatment than
plants grown without UV-B as indicated by two times higher photosynthetic rates and 12% higher relative water content. UV-B-grown
plants also had three times higher proline content. Higher tolerance to drought stress for Arabidopsis plants grown under
UV-B radiation may be attributed to both increased proline content and decreased stomatal conductance. Growth of Arabidopsis
in a UV-B-enhanced light regime increased tolerance to high light exposure and drought stress. 相似文献
4.
The response of higher plants to ionising radiation depends on factors related to both radiation properties and plant features including species, cultivar, age, and structural complexity of the target organ. Adult plants of dwarf tomato were irradiated with different doses of X-rays to investigate possible variations in leaf morpho-anatomical traits, photosynthetic efficiency, and genomic DNA. In order to assess if and how responses depend on leaf developmental stage, we analysed two types of leaves; nearly mature leaves (L1) and actively developing leaves (L2), whose lamina size corresponded to 70 and 25 %, respectively, of the lamina size of the fully expanded leaves. The results show that the X-rays prevented full lamina expansion of the L2 leaves at all doses and induced early death of tissue of plants irradiated with doses higher than 20 Gy. Most anatomical modifications were not clearly dose-dependent and the radiation-induced increase in phenolic compounds was irrespective of dose. At high doses of X-rays (50 and 100 Gy), photochemical efficiency decreased significantly in both leaf types, whereas total chlorophyll content significantly decreased only in the L2 leaves. The random amplification of polymorphic DNA data show that the X-rays induced mutagenic effects in the L2 leaves even at low doses despite the absence of severe phenotypic alterations. Genetic structure found in the population of samples corroborates the results of anatomical and eco-physiological analyses: the 20 Gy dose seems to mark the threshold dose above which genetic alterations, structural anomalies, and perturbations in the photosynthetic apparatus become significant, especially in the actively expanding leaves. 相似文献
6.
It is commonly accepted that the photosystem II subunit S protein, PsbS, is required for the dissipation of excess light energy in a process termed ‘non‐photochemical quenching’ (NPQ). This process prevents photo‐oxidative damage of photosystem II (PSII) thus avoiding photoinhibition which can decrease plant fitness and productivity. In this study Arabidopsis plants lacking PsbS (the npq4 mutant) were found to possess a competent mechanism of excess energy dissipation that protects against photoinhibitory damage. The process works on a slower timescale, taking about 1 h to reach the same level of NPQ achieved in the wild type in just a few minutes. The NPQ in npq4 was found to display very similar characteristics to the fast NPQ in the wild type. Firstly, it prevented the irreversible light‐induced closure of PSII reaction centres. Secondly, it was uncoupler‐sensitive, and thus triggered by the ΔpH across the thylakoid membrane. Thirdly, it was accompanied by significant quenching of the fluorescence under conditions when all PSII reaction centres were open ( Fo state) . Fourthly, it was accompanied by NPQ‐related absorption changes (ΔA535). Finally, it was modulated by the presence of the xanthophyll cycle carotenoid zeaxanthin. The existence of a mechanism of photoprotective energy dissipation in plants lacking PsbS suggests that this protein plays the role of a kinetic modulator of the energy dissipation process in the PSII light‐harvesting antenna, allowing plants to rapidly track fluctuations of light intensity in the environment, and is not the primary cause of NPQ or a direct carrier of the pigment acting as the non‐photochemical quencher. 相似文献
7.
Small heat shock proteins are involved in stress tolerance. We previously isolated and characterized a rice cDNA clone, Oshsp26, encoding a chloroplast-localized small heat shock protein that is expressed following oxidative or heat stress. In this
study, we transferred this gene to tall fescue plants by an Agrobacterium-mediated transformation system. The integration and expression of the transgene was confirmed by PCR, Southern, northern,
and immunoblot analyzes. Compared to the control plants, the transgenic plants had significantly lower electrolyte leakage
and accumulation of thiobarbituric acid-reactive substances when exposed to heat or methyl viologen. The photochemical efficiency
of photosystem II (PSII) (Fv/Fm) in the transgenic tall fescue plants was higher than that in the control plants during heat
stress (42°C). These results suggest that the OsHSP26 protein plays an important role in the protection of PSII during heat
and oxidative stress in vivo. 相似文献
8.
Effects of gamma and X-ray treatments were studied on three varieties of Coffea arabica (Kent, Mundo Novo and Geisha) to determine their radiosensitivity and relative biological effects. The coffee varieties seeds were subjected to 0, 50, 100, 150, 200 and 400 Gy of gamma and X-rays from Cobalt 60 (60Co) source irradiation. The irradiated seeds were pre-germinated in Petri dishes placed in a germination chamber, whilst some were sown in the greenhouse for germination studies. Data were collected on germination date and rate, root and hypocotyl length to determine the relative biological effectiveness of treatments and the optimum dose. The results showed varieties responding differently to the irradiations and doses. There was a decrease in germination with increasing doses of the irradiation. The X-ray-treated seeds had less germination percentage and seedling vigour measured at 28 days after treatment compared to the gamma-irradiated seeds. The irradiation effects on germination suggest that lower doses of X-rays give the same Relative Biological Effects as higher gamma doses for both growth chamber and greenhouse germination for Geisha at LD50, where the effects were similar for the two irradiations. Whereas 50–100 Gy stimulated germination and seedling vigour, 150 Gy adversely affected germination and no germination occurred at 200–400 Gy. The study concluded that all the coffee varieties evaluated are sensitive to gamma and X-ray irradiation in terms of germination, seedling vigour and biological effects with an optimum dose of 50–100 Gy. Therefore, both gamma and X-rays could be utilized in a future mutational breeding programme for coffee seedlings. 相似文献
9.
Human lymphocytes exposed to low doses of ionizing radiations from incorporated tritiated thymidine ([3H]dThd) or from X-rays become less susceptible to the induction of chromatid aberrations by high doses of X-rays. This indicates that low doses of ionizing radiation can produce an effect similar to the adaptive response observed with alkylating agents in prokaryotes, animal and plant cells. To determine whether there is individual variability in the adaptive response to ionizing radiations we exposed human lymphocytes from 18 different healthy donors to 'adapting' doses of [3H]dThd (0.01 microCi/ml) or X-rays (0.01 Gy) and subsequently to a 'challenge' treatment of 0.75 Gy of X-rays delivered 2 h before fixation. Four of the 18 donors did not show an adaptive response; in some cases in these individuals a synergistic response of increased, rather than decreased, damage was found. Two of these 4 donors showed no adaptive response in 3 subsequent experiments separated by 4-month intervals. This suggests that the human population exhibits a heterogeneity in the adaptive response to ionizing radiations which might be, at least in part, genetically determined. 相似文献
10.
In a previous study, we characterized a high chlorophyll fluorescence Ipal mutant of Arabidopsis thallana, in which approximately 20% photosystem (PS) Ⅱ protein is accumulated. In the present study, analysis of fluorescence decay kinetics and thermoluminescence profiles demonstrated that the electron transfer reaction on either the donor or acceptor side of PSII remained largely unaffected in the Ipa1 mutant. In the mutant, maximal photochemical efficiency (Fv/Fm, where Fm is the maximum fluorescence yield and Fv is variable fluorescence) decreased with increasing light intensity and remained almost unchanged in wildtype plants under different light conditions. The Fv/Fm values also increased when mutant plants were transferred from standard growth light to low light conditions. Analysis of PSll protein accumulation further confirmed that the amount of PSll reaction center protein is correlated with changes in Fv/Fm in Ipal plants. Thus, the assembled PSll in the mutant was functional and also showed increased photosensitivity compared with wild-type plants. 相似文献
11.
The effects of pulsed light based-LEDs at eleven frequencies (0.1, 1, 10, 50, 100, 500 Hz, 1, 5, 10, 50 and 100 kHz) programmed at 50 % duty cycle were analyzed, obtaining important parameters of the fluorescence emission of chlorophyll such as: maximum fluorescence (Fm′), minimum fluorescence, the fluorescence emission in steady state, maximum efficiency of PSII (Fv′/Fm′), the fraction of PSII centers that are open, photochemical quenching, nonphotochemical quenching (NPQ), quantum efficiency of photosystem II (ΦPSII), electron transport rate (ETR) and quantum yield of CO 2 assimilation (?CO 2). For the study and validation of the results obtained in the experiments, the analysis of variance (ANOVA) was applied 0for each parameter with confidence intervals of 95 %. The results show that the frequencies of pulsed light had positive and negative effects on the fluorescence parameters with respect to the control treatment (continuous light). The frequencies that generated the best performance of Fv′/Fm′, NPQ, ΦPSII, ETR, ?CO 2 in tomato plants were 0.1, 1, 100 Hz, and 1 kHz. The increase obtained in these parameters can represent an optimal growth and productivity conditions for optimal energy consumption. 相似文献
12.
We report the evaluation of chalcone derivatives as photosystem II (PSII) and plant growth inhibitors. Chalcone derivatives were evaluated as PSII inhibitors through Chl a fluorescence measurement. ( E)-Chalcone ( 6a ) and ( E)-3-(4-bromophenyl)-1-(4-fluorophenyl)prop-2-en-1-one ( 6j ) showed the best results, reducing the performance index on absorption basis parameter (PI abs) by 70 %. Additionally, the decrease of TR 0/RC and ET 0/RC parameters indicates that the chalcone derivatives limited the number of active PSII reaction centers and the amount of trapped energy within them. Compounds 6a and 6j both act as post-emergent herbicides at 50 μM, reducing the root biomass of the Ipomoea grandifolia weed by 72 % and 83 %, respectively, corroborating the fluorescence results. The selectivity against weeds as compared to valuable crops by compounds 6a and 6j were evaluated employing Zea mays and Phaseolus vulgaris plants. In these, our newly synthesized compounds showed no effects on biomass accumulation of roots and aerial parts when compared to the control, providing valuable evidence for the role of these compounds as selective inhibitors of the growth of undesired weeds. 相似文献
13.
Intergeneric asymmetric somatic hybrids have been obtained by the fusion of metabolically inactivated protoplasts from embryogenic suspension cultures of Festuca arundinacea (recipient) and protoplasts from a non-morphogenic cell suspension of Lolium multiflorum (donor) irradiated with 10, 25, 50, 100, 250 and 500 Gy of X-rays. Regenerating calli led to the recovery of genotypically and phenotypically different asymmetric somatic hybrid Festulolium plants. The genome composition of the asymmetric somatic hybrid clones was characterized by quantitative dot-blot hybridizations using dispersed repetitive DNA sequences specific to tall fescue and Italian ryegrass. Data from dot-blot hybridizations using two cloned Italian ryegrass-specific sequences as probes showed that irradiation favoured a unidirectional elimination of most or part of the donor chromosomes in asymmetric somatic hybrid clones obtained from fusion experiments using donor protoplasts irradiated at doses 250 Gy. Irradiation of cells of the donor parent with 500 Gy prior to protoplast fusion produced highly asymmetric nuclear hybrids with over 80% elimination of the donor genome as well as clones showing a complete loss of donor chromosomes. Further information on the degree of asymmetry in regenerated hybrid plants was obtained from chromosomal analysis including in situ hybridizations with L. multiflorum-specific repetitive sequences. A Southern blot hybridization analysis using one chloroplast and six mitochondrial-specific probes revealed preferentially recipient-type organelles in asymmetric somatic hybrid clones obtained from fusion experiments with donor protoplasts irradiated with doses higher than 100 Gy. It is concluded that the irradiation of donor cells before fusion at different doses can be used for producing both nuclear hybrids with limited donor DNA elimination or highly asymmetric nuclear hybrid plants in an intergeneric graminaceous combination. For a wide range of radiation doses tested (25–250Gy), the degree of the species-specific genome elimination from the irradiated partner seems not to be dose dependent. A bias towards recipient-type organelles was apparent when extensive donor nuclear genome elimination occurred.Abbreviations cpDNA
Chloroplast DNA
- 2, 4-D
2,4-dichlorophenoxyacetic acid
- FDA
fluorescein diacetate
- IOA
iodoacetamide
- mtDNA
mitochondrial DNA
- RFLP
restriction fragment length polymorphism 相似文献
14.
It is believed that any dose of ionizing radiation may damage cells and that the mutated cells could develop into cancer cells.
Additionally, results of research performed over the past century on the effects of low doses of ionizing radiation on biological
organisms show beneficial health effects, called hormesis. Much less is known about the cellular response to low doses of
ionizing radiation, such as those typical for medical diagnostic procedures, normal occupational exposures or cosmic-ray exposures
at flight altitudes. Extrapolating from the effects observed at higher doses to predict changes in cells after low-dose exposure
is problematic. We examined the biological effects of low doses (0.01–0.3 Gy) of γ-radiation on the membrane characteristics of erythrocytes of albino rats and carried out osmotic fragility tests and Fourier
transform infrared spectroscopy (FTIR). Our results indicate that the lowest three doses in the investigated radiation range,
i.e., 0.01, 0.025 and 0.05 Gy, resulted in positive effects on the erythrocyte membranes, while a dose of 0.1 Gy appeared
to represent the limiting threshold dose of those positive effects. Doses higher than 0.1 Gy were associated with the denaturation
of erythrocyte proteins. 相似文献
15.
Quinoa is one of the crops well-adapted to high altitude regions that can grow relatively well under drought, humid, and high UV radiation conditions. This study was performed to investigate the effects of gamma-radiation on quinoa. Seeds were treated with various doses of 50 Gy, 100 Gy, 200 Gy, 300 Gy, 400 Gy, 600 Gy, 800 Gy, and 1000 Gy. We investigated germination, as well as plant height, chlorophyll content, and normalized difference vegetation index (NDVI) at 0, 30, 44, 58, and 88 days after transplanting (DAT) and panicle weight at 88 DAT. The plants grown from the seeds treated at radiation doses greater than 200 Gy showed reduced values in most growth and physiological characteristics. The germination rate and germination speed were higher in the 50 Gy-treated seeds than in 0 Gy-treated (control) seeds. Plant height and panicle weight were highest in the plants from 50 Gy-treated seeds. Chlorophyll content was higher in all treated samples than in the controls. NDVI value showed the highest value in 0 Gy controls and plants treated with 50 Gy. The antioxidant activity was also higher in the plants from the seeds treated with 50 Gy and 100 Gy, showing a steady increase as the radiation dose increased even at 200 Gy. The plants from seeds treated with 0 Gy showed higher expression of proteins related to photorespiration and tubulin chains. The plants from seeds treated with 50 Gy induced more stress-responsive proteins. 相似文献
16.
Mutant frequency “saturation” in Arabidopsis' “main” inflorescence after fast neutron or X-ray treatment of seeds was observed using cell populations with heterogeneous radiation-sensitivities. Mutant frequencies were determined in (1) morphologically normal and conspicuous plants, (2) main and lateral inflorescences, and (3) different M1-fertility classes. At moderate radiation doses (47 Gy fast neutrons and 233 Gy X-rays) significant differences in mutant frequencies between different M1-fertility classes were observed. This suggests that cell populations with heterogeneous sensitivities were studied. No significant differences were observed either between the mutant frequencies in main and lateral inflorescences or between the ones in inflorescences of morphologically normal and conspicuous plants. This suggests that these inflorescences were formed by cell populations with similar but heterogeneous sensitivities. 相似文献
17.
Plants of C. canephora grown in pots under low nitrogen (LN) or high nitrogen (HN) applications were submitted to either cyclic water stress or daily irrigation. Water deficit led to marked decreases in net carbon assimilation rate ( A) and, to a lesser extent, in stomatal conductance ( gs), regardless of the N treatments. In well-watered plants, A appreciably increased in HN plants relative to LN plants without significant changes in gs. As a whole, changes in internal CO 2 concentration predominantly reflected changes in A rather than in gs. Under irrigated conditions, A, but not gs, correlated with leaf N concentration in a curvilinear way. Photosynthetic nitrogen-use efficiency was considerably low, and decreased with increasing leaf N concentration. Limited N, but not water, slightly decreased the maximum photochemical efficiency of photosystem II (PSII). Under continuous irrigation, LN plants had a smaller quantum yield of electron transport ( PSII) through slight decreases of photochemical quenching (q p) and capture efficiency of excitation energy by open PSII reaction centres, and increases in Stern-Volmer non-photochemical quenching. Under water-stressed conditions, changes in PSII photochemistry were apparent only in HN plants, with a 25 % decrease in PSII, due mainly to variations in q p. Biochemical constraints, rather than stomatal or photochemical limitations, provoked the decreases in A under limited supply of either N or water. 相似文献
18.
Long-lived radionuclides such as 90Sr and 137Cs can be naturally or accidentally deposited in the upper soil layers where they emit β/γ radiation. Previous studies have shown that arbuscular mycorrhizal fungi (AMF) can accumulate and transfer radionuclides from soil to plant, but there have been no studies on the direct impact of ionizing radiation on AMF. In this study, root organ cultures of the AMF Rhizophagus irregularis MUCL 41833 were exposed to 15.37, 30.35, and 113.03 Gy gamma radiation from a 137Cs source. Exposed spores were subsequently inoculated to Plantago lanceolata seedlings in pots, and root colonization and P uptake evaluated. P. lanceolata seedlings inoculated with non-irradiated AMF spores or with spores irradiated with up to 30.35 Gy gamma radiation had similar levels of root colonization. Spores irradiated with 113.03 Gy gamma radiation failed to colonize P. lanceolata roots. P content of plants inoculated with non-irradiated spores or of plants inoculated with spores irradiated with up to 30.35 Gy gamma radiation was higher than in non-mycorrhizal plants or plants inoculated with spores irradiated with 113.03 Gy gamma radiation. These results demonstrate that spores of R. irregularis MUCL 41833 are tolerant to chronic ionizing radiation at high doses. 相似文献
19.
The effect of drought on the photosynthetic functioning of two C 3 plants, Phaseolus vulgaris and Elatostema repens, has been examined. Leaf net CO 2 uptake measured in normal air was negligible at a leaf water deficit of about 30% while the calculated leaf intercellular CO 2 concentration (Ci) was unchanged. However, both the maximal photosynthetic capacity (CO 2-dependent O 2 evolution) and apparent quantum yield, measured in the presence of saturating CO 2 levels (5 to 14%), only started to decrease within the range of 25 to 30% leaf water deficit. This shows that the drought-induced inhibition seen in normal air is not caused by an inhibition of the photosynthetic mechanism, and that in this case Ci values can be misleading. Both 77 K and room-temperature fluorescence measurements indicate that the functioning of the photosystem-II reaction centre is hardly modified by water shortage. Furthermore, an analysis of photochemical chlorophyll fluorescence quenching shows, in the absence of CO 2, that O 2 can be an efficient acceptor of photosynthetic energy, even in severly dehydrated plants which do not show net CO 2 uptake in normal air. In these plants, O 2 is probably reduced mainly via Mehler-type reactions. High-light treatment given at low O 2 increases photoinhibition as measured by the decrease of apparent quantum yield in dehydrated P. vulgaris, whereas, interestingly, 1% O 2 protects dehydrated E. repens against high-light damage. The two plants could have different protective mechanisms depending upon the O 2 level or different photoinhibitory sites or mechanisms.Abbreviations and symbols Ca, Ci
ambient and calculated intercellular CO 2 concentration
- Fm, Fo, Fv
maximum, initial and variable fluorescence emission
- LWD
leaf water deficit
- PPFD
photosynthetic photon flux density
- PSII
photosystem II
- qQ
photochemical quenching of chlorophyll fluorescence 相似文献
20.
We investigated the response of the photosynthetic apparatus during an episode of extreme low winter temperature in Quercus ilex subsp. ballota (Desf.) Samp., a typical Mediterranean evergreen species in the Iberian peninsula. Both plants in a woodland located at high altitude (1,177 m. a.s.l.) and potted plants obtained from acorns of the same populations grown at low altitude (225 m. a.s.l.) were analyzed. Net CO 2 assimilation rate was negative and there was a marked decrease in photosystem II (PSII) efficiency during winter in leaves of the woodland population (high altitude individuals). These processes were accompanied by increases in non-photochemical quenching (NPQ) and in the de-epoxidated carotenoids within the xanthophyll cycle, mechanisms aimed to dissipate excess energy. In addition, these de-epoxidated carotenoids were largely preserved during the night. There was no chlorophyll bleaching during the winter, which suggests that leaves were not experiencing photoinhibitory damage. In fact, the net photosynthetic rate and the PSII efficiency recovered in spring. These changes were not observed, or were much more reduced, in individuals located at lower altitude after a few frosts. When the response to rapid temperature changes (from 20°C to –5°C and from –5°C to 20°C) was studied, it was found that the maximum potential PSII efficiency was fairly stable, ranging from 0.70 to 0.75. The rest of the photosynthetic parameters measured, actual and intrinsic PSII efficiency, photochemical and NPQ, responded immediately to the changes in temperature and, also, the recovery after cold events was practically immediate. 相似文献
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