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91.
Magnetic material in the body parts of the stingless bee Schwarziana quadripunctata, heads, pairs of antennae, thorax and abdomens, were investigated by SQUID magnetometry and Ferromagnetic Resonance (FMR).
The saturation, Js and remanent, Jr, magnetizations and coercive field Hc are determined from the hysteresis curves. From Hc and Jr/Js the magnetic particle sizes are estimated. The Js and the FMR spectral absorption areas yield 23±3%, 45±5%, 15±2% and 19±4% magnetic material contributions of head, pair of
antennae, thorax and abdomen, respectively, similar to those observed in the migratory ant Pachycondyla marginata. This result is discussed in light of the hypothesis of antennae as a magnetosensor structure. 相似文献
92.
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94.
Background and Aims
Several animals that live on bromeliads can contribute to plant nutrition through nitrogen provisioning (digestive mutualism). The bromeliad-living spider Psecas chapoda (Salticidae) inhabits and breeds on Bromelia balansae in regions of South America, but in specific regions can also appear on Ananas comosus (pineapple) plantations and Aechmea distichantha.Methods
Using isotopic and physiological methods in greenhouse experiments, the role of labelled (15N) spider faeces and Drosophila melanogaster flies in the nutrition and growth of each host plant was evaluated, as well as seasonal variation in the importance of this digestive mutualism.Key Results
Spiders contributed 0·6 ± 0·2 % (mean ± s.e.; dry season) to 2·7 ± 1 % (wet season) to the total nitrogen in B. balansae, 2·4 ± 0·4 % (dry) to 4·1 ± 0·3 % (wet) in An. comosus and 3·8 ± 0·4 % (dry) to 5 ± 1 % (wet) in Ae. distichantha. In contrast, flies did not contribute to the nutrition of these bromeliads. Chlorophylls and carotenoid concentrations did not differ among treatments. Plants that received faeces had higher soluble protein concentrations and leaf growth (RGR) only during the wet season.Conclusions
These results indicate that the mutualism between spiders and bromeliads is seasonally restricted, generating a conditional outcome. There was interspecific variation in nutrient uptake, probably related to each species'' performance and photosynthetic pathways. Whereas B. balansae seems to use nitrogen for growth, Ae. distichantha apparently stores nitrogen for stressful nutritional conditions. Bromeliads absorbed more nitrogen coming from spider faeces than from flies, reinforcing the beneficial role played by predators in these digestive mutualisms. 相似文献95.
96.
O. V. Bulda V. V. Rassadina H. N. Alekseichuk N. A. Laman 《Russian Journal of Plant Physiology》2008,55(4):544-551
The method of spectrophotometric measurement of carotenoid and chlorophyll content in extracts from plant seeds was modified. The pigments were extracted with a mixture of petroleum ether (PE) and tetrahydrofuran (THF) (PE to THF ratio 4: 1). Equations for calculations of β-carotene, lutein, chlorophyll a and b content in PE: THF mixture were obtained using specific absorption coefficients of solutions of particular pigments. It was shown that subtraction of chlorophyll contribution from the absorption spectrum of seed extracts yields spectra, which could be used in some cases for calculation of carotene and xanthophyll contents. 相似文献
97.
EPR spectroscopy is very useful in studies of the oxygen evolving cycle in Photosystem II and EPR signals from the CaMn4 cluster are known in all S states except S4. Many signals are insufficiently understood and the S0, S1, and S3 states have not yet been quantifiable through their EPR signals. Recently, split EPR signals, induced by illumination at liquid helium temperatures, have been reported in the S0, S1, and S3 states. These split signals provide new spectral probes to the S state chemistry. We have studied the flash power dependence of the S state turnover in Photosystem II membranes by monitoring the split S0, split S1, split S3 and S2 state multiline EPR signals. We demonstrate that quantification of the S1, S3 and S0 states, using the split EPR signals, is indeed possible in samples with mixed S state composition. The amplitudes of all three split EPR signals are linearly correlated to the concentration of the respective S state. We also show that the S1 → S2 transition proceeds without misses following a saturating flash at 1 °C, whilst substantial misses occur in the S2 → S3 transition following the second flash. 相似文献
98.
Xinzhi Ni Sharron S. Quisenberry Tiffany Heng-Moss John Markwell Leon Higley Frederick Baxendale Gautam Sarath Robert Klucas 《Entomologia Experimentalis et Applicata》2002,105(1):43-53
The concentration of photosynthetic pigments (i.e., chlorophylls a and b, and carotenoids) and chlorophyll degradation enzyme (i.e., chlorophyllase, oxidative bleaching, and Mg-dechelatase) activities on aphid-damaged and non-damaged regions of the infested leaves were determined with two infestation periods (6 and 12 days). Russian wheat aphid [Diuraphis noxia (Mordvilko) (Hemiptera: Aphididae)] feeding caused significant losses of chlorophylls a and b and carotenoids in the damaged regions. However, bird cherry-oat aphid [Rhopalosiphum padi (L.) (Hemiptera: Aphididae)] feeding did not, except a significantly lower level of carotenoids was observed in the damaged regions from the short-infestation (6-day) samples. Interestingly, the non-damaged regions of D. noxia-infested leaves on both sampling dates had a significant increase of chlorophylls a and b and carotenoid concentrations when compared with the uninfested leaves. Although D. noxia feeding did not cause any changes in either chlorophyll a/b or chlorophyll (a+b)/carotenoid ratio between the damaged and non-damaged leaf regions on short-infestation (6-day) samples, a significantly lower chlorophyll a/b ratio was detected in long-infestation (12-day) samples. The assays of chlorophyllase and oxidative bleaching activities showed no significant differences between the damaged and non-damaged regions of the infested leaves on either sampling date. Mg-dechelatase activity, however, was significantly higher in D. noxia-damaged than non-damaged leaf regions from the short-infestation samples, while no differences were detected from the long-infestation samples. Furthermore, the long-infestation samples showed that Mg-dechelatase activity from both D. noxia-damaged and non-damaged regions increased significantly in comparison with the respective regions of either uninfested or R. padi-infested leaves. We infer that non-damaged regions of D. noxia-infested leaves compensate for the pigment losses in the damaged regions, and that Mg-dechelatase activity changed dynamically from a localized response to a systemic response as infestation duration extends. The findings from this study on cereal aphid-elicited chlorosis (or desistance) would help us to elucidate plant resistance mechanisms, in particular plant tolerance to non-defoliating herbivory. 相似文献
99.
Effect of Seawater on Photosynthesis and Dry Matter Accumulation in Developing Rice Grains 总被引:1,自引:0,他引:1
To understand the physiology of rice under seawater salinity, potted rice plants were irrigated with different concentrations of Japan seawater (electrical conductivity 0.9, 5.7, 11.5, or 21.5 mS cm-1) from 10 d after transplanting (DAT) to 35 DAT, and from 75 to 100 DAT. Seawater salinity decreased the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, leaf water and osmotic potentials, and relative water content, and increased leaf temperature. The contents of chlorophylls, carotenoids, and total sugars significantly decreased in the leaves but content of non-reducing sugars decreased only slightly. With increasing salinity the Na+ concentration increased, while Ca2+, Mn2+, and K+ concentrations decreased. Salinity decreased the contents of sugars and proteins, dry mass, and rate of dry mater accumulation in developing grains. 相似文献
100.
Spectroanalysis in native gels (SING): rapid spectral analysis of pigmented thylakoid membrane complexes separated by CN–PAGE 下载免费PDF全文
Ben Lucker Eliezer Schwarz Sebastian Kuhlgert Elisabeth Ostendorf David M. Kramer 《The Plant journal : for cell and molecular biology》2017,92(4):744-756
Photosynthetic organisms rapidly adjust the capture, transfer and utilization of light energy to optimize the efficiency of photosynthesis and avoid photodamage. These adjustments involve fine‐tuning of expression levels and mutual interactions among electron/proton transfer components and their associated light‐harvesting antenna. Detailed studies of these interactions and their dynamics have been hindered by the low throughput and resolution of currently available research tools, which involve laborious isolation, separation and characterization steps. To address these issues, we developed an approach that measured multiple spectroscopic properties of thylakoid preparations directly in native polyacrylamide gel electrophoresis gels, enabling unprecedented resolution of photosynthetic complexes, both in terms of the spectroscopic and functional details, as well as the ability to distinguish separate complexes and thus test their functional connections. As a demonstration, we explore the thylakoid membrane components of Chlamydomonas reinhardtii acclimated to high and low light, using a combination of room temperature absorption and 77K fluorescence emission to generate a multi‐dimensional molecular and spectroscopic map of the photosynthetic apparatus. We show that low‐light‐acclimated cells accumulate a photosystem I‐containing megacomplex that is absent in high‐light‐acclimated cells and contains distinct LhcII proteins that can be distinguished based on their spectral signatures. 相似文献