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The spectral transmittance of isolated 'intact' upper and lower epidermes
as well as the extractable UV-B-absorbing capacity of epidermes and
mesophyll were studied in the leaves of exposed and deeply shaded,
field-grown plants of Urginea maritima (L.) Baker.
Epidermal transmittance in the visible part of the spectrum was high
(>80%) in all cases. Transmittance in the UV-B (280-320 nm) was
comparatively high (c. 14%) in both the upper and
lower epidermes of shaded plants, but more than an order of magnitude lower
in exposed plants, with the lowest values observed on the upper leaf
epidermis. UV-B transmittance was negatively correlated with the methanol
extractable UV-B-absorbing capacity of the epidermes, but was independent
of epidermal thickness. The UV-B-absorbing capacity of the mesophyll, when
expressed on an area basis, was not affected by exposure. However, it was
significantly higher in shaded plants, when expressed on a dry mass basis.
The results indicate that although the concentrations of the UV-B-absorbing
components of the whole leaf or its epidermis fluctuate according to the
site-dependent radiation stress, the opposite is evident for the mesophyll.
Therefore, high irradiance in U. maritima, apart from
inducing an increase in UV-B-absorbing compounds on a whole leaf basis,
also caused a change in the distribution of these compounds between
epidermis and mesophyll. 相似文献
2.
Effects of three endophytic entomopathogens on sweet sorghum and on the larvae of the stalk borer Sesamia nonagrioides 下载免费PDF全文
Spiridon Mantzoukas Christos Chondrogiannis George Grammatikopoulos 《Entomologia Experimentalis et Applicata》2015,154(1):78-87
Various endophytic fungi of native plants and crops are important entomopathogens. The objective of this study was to investigate the entomopathogenic action of Beauveria bassiana (Balsamo) Vuillemin, Metarhizium robertsii (Metchnikoff) Sorokin, and Isaria fumosorosea (Wize) Brown & Smith (all Ascomycota: Hypocreales) against larvae of Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) artificially introduced into Sorghum bicolor L. (Moench) (Poaceae) plants under natural environmental conditions. Sorghum bicolor is an economically important crop cultivated for grain, fiber, forage, and lately for biofuel, and S. nonagrioides is its main pest in Mediterranean areas. Young sorghum plants were inoculated with the entomopathogens by spraying in the field. Plant water status, chlorophyll concentration, photosynthesis, and transpiration were not affected. Thirty days after endophyte establishment, plants were infested with fourth instars of S. nonagrioides. The endophytes prevented 50–70% of larvae from entering stalks. Larval mortality was 70–100% and tunnel lengths were reduced by 60–87%. Larval infestation resulted in reduced electron transport capacity and net photosynthetic rate, which was ameliorated in the presence of I. fumosorosea and reversed by B. bassiana and M. robertsii. The growth of sorghum was unaffected in all treatments during the experimental period. Beauveria bassiana and M. robertsii can protect sweet sorghum from damage induced by S. nonagrioides under natural environmental conditions without affecting plant physiology and growth. 相似文献
3.
Grammatikopoulos George Drilias Periklis Kyparissis Aris Petropoulou Yiola Manetas Yiannis 《Plant Ecology》2001,154(1-2):117-122
The effects of sub-ambient levels of UV-B radiation on the shrub Rosmarinus officinalis L. were investigated in a field filtration experiment in which the ambient UV-B was manipulated by a combination of UV-B transmitting and UV-B absorbing filters. As a result, the plants were receiving near-ambient or drastically reduced UV-B radiation doses. Drastic reduction of UV-B radiation had no effect on mean, total and maximum stem length, number of stems per plant, dry mass of leaves, stems and roots and leaf nitrogen and phenolic contents. However, flowering was more pronounced under reduced UV-B radiation during the winter period which coincides with ascending ambient UV-B radiation. In contrast, during autumn and early winter, a period which coincides with descending ambient UV-B radiation, flowering was unaffected by reduced UV-B radiation. We can conclude that natural UV-B radiation does not affect growth of Rosmarinus officinalis, but its reduction could influence the flowering pattern of the species. 相似文献
4.
Characterization of the vacuolar-type H+-ATPase from guard cell protoplasts of Commelina 总被引:1,自引:0,他引:1
Willmer C.M.; Grammatikopoulos G.; Lascve G.; Vavasseur A. 《Journal of experimental botany》1995,46(4):383-389
Characteristics of the vacuolar-type (V-type) H+-ATPase fromguard cell protoplasts of Commelina communis L. were investigatedusing a linked enzyme assay and nitrate inhibition as a diagnosticindicator of the enzyme activity. ATPase activity was completelyinhibited by about 50 mol m3 nitrate and activity wasoptimal near pH 8.0. The temperature optimum for activity wasabout 37 C and an Arrhenius plot indicated changes in activationenergy for the ATPase at 15C and possibly at about 30 C. Theenzyme was stimulated by Cl while Ca2+ inhibited activity(l50 = 1.5 mol m3). The apparent Km (MgATP) was 0.62mol m3. Incubation of guard cell protoplasts for up to 5 h in 50 µMabscisic acid (ABA) or 25µM fusicoccin (FC) did not affectsubsequent ATPase activity. In vitro assays with FC or ABA alsodid not affect enzyme activity. Activity was not affected bylight or potassium ferricyanide, two factors which are knownto influence stomatal activity. Beticoline was a potent inhibitorof activity (l50 = 50 µM) while DCCD was less effective(l50 = 90µM). On chlorophyll, protein and protoplast bases, V-type ATPaseactivity was greater in guard cell protoplasts than mesophyllcell protoplasts by 66, 13.9 and 1.9, respectively. On atonoplast surface area basis the enzyme activity was 5.6 timeshigher in guard cell protoplasts than in mesophyll cell protoplasts Thus, although the characteristics of the V-type, H +-ATPaseof GCP are very similar to those found in other cell types,rates of activity and probably tonoplast enzyme density aremuch greater in guard cell protoplasts than mesophyll cell protoplastsof C. communis which corresponds with the large and rapid ionfluxes across the tonoplast associated with stomatal movements Key words: Guard cell protoplasts, stomata, V-type H +-ATPase 相似文献
5.
E. Levizou P. Karageorgou Y. Petropoulou G. Grammatikopoulos Y. Manetas 《Biologia Plantarum》2004,48(2):305-307
Thirteen flavonoid aglycons, contained in the strongly allelopathic epicuticular exudates of Dittrichia viscosa, were investigated for their effects on lettuce seedling radicle growth. Concerning radicle length and mass, variable results
were obtained, with most of the substances having no effect, some being inhibitory and some even promotive. Shoot mass was
slightly reduced in four cases. Seed germination rates, root hair and lateral root formation were not affected either. Three
of the compounds (namely quercetin 3,3-dimethylether, naringenin and eriodictyol) induced a strong ageotropic response in
radicle growth.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
7.
Phlomis fruticosa is one of the main species of post-fire Mediterranean communities, occupying areas with post-fire grazing or altered precipitation
pattern and consequently water stress imposed on seedlings of co-occurring species. Seedlings of woody perennials often differ
from their mature individuals regarding their resistance of photosynthetic performance to environmental stresses. Such differences
have been reported for tree species but there is a lack of information regarding shrub species. In the present study, we tried
to detect changes in (PSII) activity imposed by water stress in P. fruticosa seedlings as well as its capability for recovery after rehydration. Maximum PSII photochemical efficiency decreased only
under severe water stress exactly as in mature plants in the field. However, leaf chlorophyll (Chl) content was almost stable
regardless of leaf relative water content (RWC). We assume that the photoprotective chlorophyll loss process, reported for
many mature Mediterranean species (including P. fruticosa), has not yet been developed at the seedling stage. On the other hand, photoprotection through an increase of the relative
amount of non-QB-reducing centers was found during dehydration. Non-photochemical quenching (NPQ) contributed to protection from photodamage
until moderate water stress but was significantly suppressed under severe water stress. Both processes were reversed after
rehydration. The above characteristics enabled seedlings not only to survive during aggravating drought but also to maintain
a considerable part of their effective quantum yield and perform significant electron transport even at extremely low relative
water content (RWC). This was confirmed with measurements in a semi-natural environment (pots) and under real steady state
conditions regarding adaptation of the photosynthetic machinery to prevailing light intensities. 相似文献
8.
Sushant Kumar Theodore Pavloudis Vidyadhar Singh Hoa Nguyen Stephan Steinhauer Christopher Pursell Bruce Clemens Joseph Kioseoglou Panagiotis Grammatikopoulos Mukhles Sowwan 《Liver Transplantation》2018,8(4)
The application of Mg for hydrogen storage is hindered due to the slow absorption of hydrogen in Mg films. Herein, the hydrogenation process is explored theoretically using density functional theory calculations, and energy barriers are compared for hydrogen diffusion through Pd nanoparticle/Mg film interfaces and their variations, i.e., Pd(H)/Mg(O). Decomposing the mechanism into basic steps, it is shown that Pd undergoes a strain‐induced crystallographic phase transformation near the interface, and indicated that hydrogen saturation of Pd nanoparticles enhances their efficiency as nanoportals. Using energetic arguments, it is explained why hydrogen diffusion is practically prohibited through native Mg oxide and seriously suppressed through existing hydride domains. Hydrogen flux is experimentally investigated through the nanoportals in Pd‐nanoparticle decorated Mg films by pressure‐composition isotherm measurements. An r ≈ t1/3 relationship is theoretically calculated for the radial growth of hemispherical hydride domains, and this relationship is confirmed by atomic force microscopy. The diffusion constant of hydrogen in Mg films is estimated as DHfilm ≈ 8 × 10?18 m2 s?1, based on transmission electron microscopy characterization. The unique nanoportal configuration allows direct measurement of hydride domain sizes, thus forming a model system for the experimental investigation of hydrogenation in any material. 相似文献
9.
Hydrogen Storage: Hydrogen Flux through Size Selected Pd Nanoparticles into Underlying Mg Nanofilms (Adv. Energy Mater. 4/2018) 下载免费PDF全文
10.
Kyparissis Aris Drilias Periklis Petropoulou Yiola Grammatikopoulos George Manetas Yiannis 《Plant Ecology》2001,154(1-2):187-193
Seedlings of Ceratonia siliqua L. were grown for 1 year in the field under ambient or ambient plus supplemental UV-B radiation (corresponding to 15% ozone depletion over Patras) and received two levels of additional irrigation during the summer dry period. The experiment was started during February 1998 and two major samplings were performed, the first at the end of the dry period (September 1998) and the second at the end of the experiment (January 1999). Plants receiving additional irrigation showed significantly higher leaf number, plant height and chlorophyll content at the end of the summer, but these differences were abolished at the final harvest. Plants growing under enhanced UV-B radiation had significantly fewer leaves and less nitrogen content at the end of the dry period, but these effects were also abolished at the final harvest, during which significant UV-B induced increases in stem dry mass were observed. None of the other measured parameters (mean leaf area, leaf dry mass, leaf thickness, UV-B absorbing compounds, phenolics, tannins and photochemical efficiency of PSII) were affected by either treatment. Combined UV-B / water effects were not significant. We may conclude that although some minor responses to enhanced UV-B radiation were evident, C. siliqua is resistant against UV-B radiation damage at the level applied. 相似文献
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