排序方式: 共有69条查询结果,搜索用时 0 毫秒
1.
Low-molecular-weight aliphatic carboxylic acids in soil solutions under different vegetations determined by capillary zone electrophoresis 总被引:5,自引:0,他引:5
Concentrations of low-molecular-weight aliphatic carboxylic acids in soil solution were determined by a newly developed capillary
zone electrophoresis method. Soil solution samples were collected by centrifugation of soil from the A horizon of a Danish,
homogeneous, nutrient-rich Hapludalf in adjacent forested and arable plots. The forested plots of 0.5 ha were 33-year old
stands of beech (Fagus sylvatica L.), oak (Quercus robur L.), grand fir (Abies grandis Lindl.), and Norway spruce (Picea abies
(L.) Karst.), while sugar beet (Beta vulgaris L.) and winter wheat (Triticum aestivum L.) were the agricultural crops this
year. High variability in soil solution concentrations of metal cations (Al, Ca, K, Mg, Na), monocarboxylic acids (formic,
acetic, lactic, and valeric acids), and di- and tricarboxylic acids (oxalic, malic, succinic, and citric acids) were found
within each plot. Despite this short-range within-plot variability, higher concentrations of di- and tricarboxylic acids were
found in the forested soils than in the arable soils. The vegetation seemed to favour some monocarboxylic acids, but the total
monocarboxylic acid concentrations showed little relation to the vegetation. Probably due to much less soil water in the Norway
spruce plot, the low-molecular-weight aliphatic carboxylic acid concentrations in the samples from that plot were much higher
than those found in samples from the other plots. Carbon in low-molecular-weight aliphatic carboxylic acids only accounts
for a few percent of dissolved organic carbon, and no general relation was found between carbon in low-molecular-weight aliphatic
carboxylic acids and dissolved organic carbon, although the correlation between carbon in di- and tricarboxylic acids and
dissolved organic carbon was significant.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Composition and reactivity of DOC in forest floor soil solutions in relation to tree species and soil type 总被引:8,自引:0,他引:8
Bjarne W. Strobel Hans Christian Bruun Hansen Ole K. Borggaard Martin K. Andersen Karsten Raulund-Rasmussen 《Biogeochemistry》2001,56(1):1-26
Metal coordinating propertiesof DOC (dissolved organic carbon), and henceits influence on heavy metal release andmineral weathering, depend on the compositionand properties of DOC. Tree species producelitter with different chemical composition anddegradability, and these differences mightinfluence the composition and reactivity of DOCin soil solutions. Accordingly, analysis ofcomposition and reactivity of DOC in soilsolution samples collected by centrifugationfrom 16 forest soil O horizons from the fourtree species beech (Fagus sylvatica L.),oak (Quercus robur L.), grand fir (Abies grandis Lindl.), and Norway spruce (Picea abies (L.) Karst.) on two clayey and twosandy soils were carried out. The compositionand properties of DOC were determined bycapillary zone electrophoresis, acid-basetitration, Cu ion titration, total elementalanalysis, IR and UV spectroscopy, and metalrelease assays. Concentrations of DOC rangedfrom 20 to 163 mM with pH ranging from 4.6 to7.3. Norway spruce produced the highest DOCconcentration, and the lowest pH. Carbon inlow-molecular-weight aliphatic carboxylic acids(LACA) accounted for less than 6% of DOC withformic and acetic acids as the most abundantLACAs. The DOC was cation exchanged and protonsaturated to obtain comparable forms of DOC.Titratable carboxylic acid and phenolic groupswere in the range 51 to 82 and 20 to64 mmol·mol–1 C, respectively, with fewerphenolic groups in grand fir DOC as the onlysignificant difference. Infrared spectra offreeze-dried DOC samples suggest low contentsof aromatic C in the DOC especially from grandfir stands. Stability constants, log K of Cu-DOC complexes, determined by Cu ion titrationof DOC samples with fitting of the data to atwo-site binding model, were in the range 5.63to 6.21 for the strong binding sites and 3.58to 4.10 for the weak sites, but with nosignificant effects of tree species or site.Freeze-dried DOC samples were found to consistof 41 to 45% C, 38 to 49% O, 4.4 to 5.4% Hand 1.2 to 2.0% N and C/N ratios in the range26 to 42. Reactivity of DOC in terms of releaserates of Cd, Cu and Fe cations from a soilsample (flow cell experiments) showed nosignificant differences among DOC samples fromdifferent tree species and soil types.Apparently, only minor differences occur inchemical composition and reactivity ofequivalent concentrations of DOC in forestfloor soil solutions irrespective of origin,i.e. four tree species and two soil types. Soilsolution pH and the concentration of DOCproduced by various tree species are thecritical parameters when distinguishing amongtree species in relation to heavy metal releaseand mineral weathering. 相似文献
3.
4.
Valentina?V.?Grigorjeva Nina?GabarayevaEmail authorView authors OrcID profile
return OK on get 《Protoplasma》2018,255(1):109-128
By a detailed ontogenetic study of Polemonium caeruleum pollen, tracing each stage of development at high TEM resolution, we aim to understand the establishment of the pollen wall and to unravel the mechanisms underlying sporoderm development. The main steps of exine ontogeny in Polemonium caeruleum, observed in the microspore periplasmic space, are spherical units, gradually transforming into columns, then to rod-like units (procolumellae), the appearance of the initial tectum, growth of columellae in height and tectum in thickness and initial sporopollenin accumulation on them, the appearance of the endexine lamellae and of dark-contrasted particles on the tectum, the appearance of a sponge-like layer and of the intine in aperture sites, the appearance of the foot layer on the base of the sponge-like layer and of spinules on the tectum, and massive sporopollenin accumulation. This sequence of developmental events fits well to the sequence of self-assembling micellar mesophases. This gives (together with earlier findings and experimental exine simulations) strong evidence that genome and self-assembly probably share control of exine formation. It is highly probable that self-assembly is an intrinsic instrument of evolution. 相似文献
5.
Mayara?Pereira?Gon?alves Maria?Olívia?Mercadante-Sim?esEmail authorView authors OrcID profile
return OK on get Leonardo?Monteiro?Ribeiro 《Protoplasma》2018,255(6):1713-1724
Latex is a complex plant secretion with both ecological and economic importance. There is little information currently available on the cytological aspects of the ontogenesis of anastomosed laticifers, the ducts originating through the lysis of adjacent cell walls. Hancornia speciosa is a tree typical of the Cerrado (neotropical savanna) biome. Its latex has medicinal value and is also used to produce rubber. The ontogenesis of its laticifers and the process of latex synthesis are described here. Structural, cytochemical, and ultrastructural analyses of the stem apex and phytochemical analyses of the latex were performed. Laticifer ontogenesis begins early in promeristem cells and subsequently extends through the procambial region. The laticifer precursor cells demonstrate intense metabolic activity, evidenced by starch accumulation and the proliferation of mitochondria, dictyosomes, endoplasmic reticulum, and ribosomes—resulting in the thickening of the cell walls and accumulations of oil droplets in the cytoplasm and fibrous materials in the vacuoles. The ontogenetic process culminates with the partial dissolution of adjacent cell walls and the collapse of the cytoplasm, giving rise to anastomosed laticifers distributed throughout the phloem and adjacent regions of the cortex and medulla. The latex itself is composed of terpenes, mucilage, proteins, alkaloids, and organelle residues that form an emulsion. Laticifer development takes place in three phases: (1) the formation of the emulsion in the promeristem, (2) anastomosis and the collapse of the cytoplasm in the distal region of the procambium, and (3) the maturation of laticifers and latex storage in a central vacuole in the proximal region of the procambium. 相似文献
6.
Julia?M.?MininaEmail authorView authors OrcID profile
return OK on get Tatjana?V.?Karamysheva Nicolaj?B.?Rubtsov Natalia?S.?Zhdanova 《Protoplasma》2018,255(5):1477-1486
Previously, we described the unique feature of telomeric regions in Iberian shrew Sorex granarius: its telomeres have two ranges of size, very small (3.8 kb of telomeric repeats on average) and very large discontinuous telomeres (213 kb) interrupted with 18S rDNA. In this study, we have demonstrated extraordinary replication pattern of S. granarius large telomeres that have not been shown before in other studied mammal. Using the ReD-FISH procedure, we observed prolonged, through S period, large telomere replication. Furthermore, revealed ReD-FISH asymmetric signals were probably caused by partial replication of telomeres within an hour of 5-bromodeoxyuridine treatment due to the large size and special organization. We also found that in contrast to the telomeric halo from primary fibroblasts of bovine, mink, and common shrew, telomere halo of S. granarius consists of multiple loops bundled together, some of which contain rDNA. Here, we suggested several replicons firing possibly stochastic in each large telomere. Finally, we performed the TIF assay to reveal DNA damage responses at the telomeres, and along with TIF in nuclei, we found large bodies of telomeric DNA and ?-H2AX in the cytoplasm and on the surface of fibroblasts. We discuss the possibility of additional origin activation together with recombination-dependent replication pathways, mainly homologous recombination including BIR for replication fork stagnation overcoming and further S. granarius large telomere replication. 相似文献
7.
Jind?i?ka?AngeliniEmail authorView authors OrcID profile
return OK on get Stanislav?Vosolsobě Petr?Sk?pa Angela?Yeuan?Yen?Ho Erica?Bellinvia Olga?Valentová Jan?Marc 《Protoplasma》2018,255(4):1195-1204
The dynamic microtubule cytoskeleton plays fundamental roles in the growth and development of plants including regulation of their responses to environmental stress. Plants exposed to hyper-osmotic stress commonly acclimate, acquiring tolerance to variable stress levels. The underlying cellular mechanisms are largely unknown. Here, we show, for the first time, by in vivo imaging approach that linear patterns of phospholipase Dδ match the localization of microtubules in various biological systems, validating previously predicted connection between phospholipase Dδ and microtubules. Both the microtubule and linear phospholipase Dδ structures were disintegrated in a few minutes after treatment with oryzalin or salt. Moreover, by using immunofluorescence confocal microscopy of the cells in the root elongation zone of Arabidopsis, we have shown that the cortical microtubules rapidly depolymerized within 30 min of treatment with 150 or 200 mM NaCl. Within 5 h of treatment, the density of microtubule arrays was partially restored. A T-DNA insertional mutant lacking phospholipase Dδ showed poor recovery of microtubule arrays following salt exposition. The restoration of microtubules was significantly retarded as well as the rate of root growth, but roots of overexpressor GFP-PLDδ prepared in our lab, have grown slightly better compared to wild-type plants. Our results indicate that phospholipase Dδ is involved in salt stress tolerance, possibly by direct anchoring and stabilization of de novo emerging microtubules to the plasma membrane, providing novel insight into common molecular mechanism during various stress events. 相似文献
8.
Lu?Liu Bao-Zhen?HuaEmail authorView authors OrcID profile
return OK on get 《Protoplasma》2018,255(4):1121-1128
The larvae of Bittacidae, a cosmopolitan family in Mecoptera, have an interesting habit of spraying the body surface with soil through the anus after hatching, and each molts. The fine structure of Malpighian tubules, however, remains largely unknown in the larvae of Bittacidae to date. Here, we studied the ultrastructure of the larval Malpighian tubules in the hangingfly Terrobittacus implicatus (Huang & Hua) using scanning and transmission electron microscopy. The larvae of T. implicatus have six elongate Malpighian tubules at the junction of the midgut and hindgut. The tubule comprises a basal lamina, a single-layered epithelium, and a central lumen. The basal plasma membranes of the epithelial cells are conspicuously infolded and generate a labyrinth. The epithelium consists of two types of cells: large principal cells and scattered stellate cells. Mitochondria and cisterns of rough endoplasmic reticulum are numerous in the principal cells but are sparsely distributed in the stellate cells, indicating that the principal cells are active in transport. On the other hand, spherites are only abundant in the principal cells and are likely associated with the soil-spraying habit of the larvae. 相似文献
9.
Thomas?B?rnerEmail authorView authors OrcID profile
return OK on get 《Protoplasma》2017,254(5):1845-1855
DNA and machinery for gene expression have been discovered in chloroplasts during the 1960s. It was soon evident that the chloroplast genome is relatively small, that most genes for chloroplast-localized proteins reside in the nucleus and that chloroplast membranes, ribosomes, and protein complexes are composed of proteins encoded in both the chloroplast and the nuclear genome. This situation has made the existence of mechanisms highly probable that coordinate the gene expression in plastids and nucleus. In the 1970s, the first evidence for plastid signals controlling nuclear gene expression was provided by studies on plastid ribosome deficient mutants with reduced amounts and/or activities of nuclear-encoded chloroplast proteins including the small subunit of Rubisco, ferredoxin NADP+ reductase, and enzymes of the Calvin cycle. This review describes first models of plastid-to-nucleus signaling and their discovery. Today, many plastid signals are known. They do not only balance gene expression in chloroplasts and nucleus during developmental processes but are also generated in response to environmental changes sensed by the organelles. 相似文献
10.
Priyanka?Varun S.?A.?Ranade Sangeeta?SaxenaEmail authorView authors OrcID profile
return OK on get 《Protoplasma》2017,254(6):2055-2070
Papaya leaf curl disease (PaLCuD) caused by papaya leaf curl virus (PaLCuV) not only affects yield but also plant growth and fruit size and quality of papaya and is one of the most damaging and economically important disease. Management of PaLCuV is a challenging task due to diversity of viral strains, the alternate hosts, and the genomic complexities of the viruses. Several management strategies currently used by plant virologists to broadly control or eliminate the viruses have been discussed. In the absence of such strategies in the case of PaLCuV at present, the few available options to control the disease include methods like removal of affected plants from the field, insecticide treatments against the insect vector (Bemisia tabaci), and gene-specific control through transgenic constructs. This review presents the current understanding of papaya leaf curl disease, genomic components including satellite DNA associated with the virus, wide host and vector range, and management of the disease and suggests possible generic resistance strategies. 相似文献