摘要:

AbstractSince the fundamental work of the botanist Ernst Munch there has been a clear differentiation between a symplastic and an apoplastic compartment of plants, separated by the plasmalemma. In contrast to the symplast, the apoplast was considered as being dead and hence attracted little interest. It is not before the late seventies of this century that plant scientists realised that processes such as growth and differentiation as well as signal transduction may not be understood without accounting for apoplastic processes. Since then growing evidence has supported the view that apoplastic properties are of significance for such diverse processes as genotypic variation in nutrient efficiency and tolerance against adverse ion relations, for plant/microbe interaction, or for water and nutrient transport.In this contribution we review apoplastic properties and processes in relation to plant mineral nutrition. Examples are taken from work being conducted in the scope of the special research project of the German Research Foundation “The apoplast of higher plants: compartment for storage, transport and reactions” and especially from own w

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610502

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe plant cell wall is essential to almost every aspect of plant life. The cell wall is a dynamic and highly ordered complex of polysaccharides, structural proteins and phenolics. The introduction of new techniques in the study of cell‐wall architecture, namely the availability of antibodies to cell wall components, new methods in electron microscopy, application of physico‐chemical techniques like FTIR and NMR as well as refined biochemical analyses have substantially changed our conception of the cell wall. The extracellular matrix is no longer understood as a static, mainly covalently cross‐linked macromolecular structure but as a flexible, developmentally regulated network that is largely based on non‐covalent interactions. Three principally independent but interacting networks that form local microdomains can be distinguished: The cellulose‐microfibril ‐ xyloglucan network, the network of pectins and the network of structural cell wall proteins. This review summarizes the current ideas about the architecture and biochemical composition of primary

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610503

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractRecent attention has been drawn to plant‐growth‐promoting bacteria which colonize not only the rhizosphere and the surface of roots but also the interior of roots and shoots of higher plants. The bacteria are found in the apoplast i.e. intercellular spaces and xylem vessels. These so‐called endophytic bacteria are considered to be more effective in providing the host plant with nitrogen than associative rhizosphere bacteria on the root surface and appear to play an important role in biological nitrogen fixation (BNF) in nonleguminous plants. This is discussed in detail. Bacteria which have been found in the apoplast of nonleguminous plants includeAzospirillum spp., Pantoea agglomerans, Acetobacter diazotrophicus, Herbaspirillum spp., Azoarcus spp.andRhizobium spp.The significance of the apoplastic colonization of these bacteria for the nitrogen nutrition of tropical non‐legumes is di

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610504

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractNutrient ions entering the plant root from the soil solution, whether directly or through mycorrhizal fungi, first encounter the apoplast, a chemically complex compartment. The movement of ions in unmodified walls occurs in water‐filled channels (diameter about 10 nm) and is influenced by electrical charges. Some positive charges occur in the wall, but the majority are negative. The permeability of the wall is variable, depending on its age and whether or not it has been further modified. Very young walls are less permeable than older walls, and the permeability of mature walls may be reduced by suberin and/or lignin deposits. It is not clear whether or not the other two main wall‐modifying substances, mucilages and condensed tannins, also significantly reduce wall permeability. Casparian bands, which consist of suberin and lignin within radial and transverse walls, occur in the endodermis and exodermis. These layers form continuous cylinders within the root so that ion movement into the entire areas they surround is prevented. An important corollary is that Casparian bands dictate which cells are accessed by the soil solution and thus are in a position to absorb ions. It is postulated that a Casparian band‐like modification also occurs in the walls of cork cells, based on observations of their impermeability to dyes. Suberin can occur in the form of lamellae which are deposited on all walls of endodermal, exodermal and cork cells. Unlike the Casparian bands, these lamellae limit movement between the apoplast and plasmalemma surface of the individual cells in which they occur. Condensed tannins, an addition to the walls of tree roots which results in them becoming brown, appear to function as antimicrobial agents rather than as permeability barriers. Further research is needed to investigate the structure of both unmodified and modified walls in a variety of species and under a variety of growing condi

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610505

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractIt is now well established that calcium has a substantive role in intracellular signalling in stomatal guard cells. Much less attention has, however, been paid to the importance of maintaining an apoplastic calcium concentration which permits this mechanism to operate. Data are presented for the calcicoleLeontodon hispidus, in which the xylem sap may contain over 16 mM free calcium, showing that the concentration of calcium in the guard cell apoplast may be as low as 0.10 mM. This appears to be achieved by the deposition of considerable amounts of calcium oxalate in the mesophyll, particularly in the palisade tissue. Of the calcium delivered directly into the epidermis by the transpiration stream, a large proportion is diverted into the trichomes.It seems unlikely that stomatal regulation over long distances (e.g. from root to shoot) is accomplished via apoplastic calcium, but over shorter distances (the span of a few cells in the epidermis) signalling via calcium in the apoplast is entirely feasible and it is worthy of further investigation.

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610506

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractEnvironmental damages like forest decline in Northern Slovakia could be a result of long‐distance transport of pollutants with the dominating north‐west winds. On 10 sites, primarily in the northbound upper slopes of west‐east oriented mountain ranges in Northern Slovakia, the extent of the heavy metal contamination in soils along a north‐south transect was examined. Oi, Oe, Oa, A, and B horizons were sampled and the total concentrations of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined. The ranges of heavy metal concentrations in the forest floor were higher than reported for comparable samples from Bavarian soils except for Zn (Cd: 0.65–1.77; Cr: 12–40; Cu: 19–41; Ni: 8–24; Pb: 70–187; Zn: 31–92 mg kg−1), in the mineral soil the concentrations were lower. The depth distribution of the metal concentrations indicated a contamination with Cd, Cr, Cu, Ni, Pb, and Zn. The concentration differences between forest floor and mineral soil tended to be higher at the northern than at the southern sites for Cu, Ni, Pb, and Zn, indicating a long‐distance transport from the north. Correlation and principal component analyses of the total metal concentrations revealed three groups: Cu, Pb, and Zn inputs mainly seemed to result from long‐distance transport from the north, Cr and Ni inputs additionally from local sources. Cd probably had its origin mainly in local sources. This result was further confirmed by the grouping of

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610507

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe buffering of protons and hydroxyl ions in acid soils was studied by the addition of small amounts of HCl, H2SO4, and NaOH in consecutive batch experiments using surface soils and subsoils from two Cambisols and one Podzol. A chemical equilibrium model was used to study the main buffer processes. The model included inorganic complexation and multiple cation exchange, and also the solubility of jurbanite and Al(OH)3for the subsoils.Buffering of protons was predicted quite well by the model for the surface soil of the Spodi‐Dystric and Spodic Cambisols, suggesting that multiple cation exchange was the main buffer process. For the Podzol surface soil, however, the model overestimated proton buffering by cation exchange considerably. Hydroxyl buffering in acid surface soils could be described well by the model for the Podzol soil only. For the Cambisols, hydroxyl buffer reactions included not only cation exchange, but also solubilization of large amounts of organic matter and presumably deprotonation of dissolved organic carbon (DOC).Modelling proton and hydroxyl buffering in subsoils suggested that equilibrium with AJ(OH)3was not maintained for the Podzol and spodic Cambisol. Sulphate sorption had to be considered to describe titration experiments in all three soils. The assumption of jurbanite being in equilibrium with soil extracts was useful only for the Spodi‐Dystric Cambi

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610508

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractOn a sandy tropical soil, organic materials (prunings ofLeucaena leucocephala, Senna siameaand maize stover) with contrasting C/N ratio (13, 18 and 56, respectively) were applied at the rate of 15 t ha−1a−1in order to increase the amount of soil organic matter. Two light fractions (LF1 = LF>2 mm and LF2 = 0.25 mm

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610509

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractSteppenböden Rußlands sind vielfach reich an organischem C (Corg) und aus relativ homogenem Substrat. Sie eignen sich deshalb gut zur Prüfung der Frage, ob und in welchem Umfang Klimafaktoren C‐ und N‐Pools beeinflussen. Hierzu wurden von 10 zonalen “Steppenböden” Rußlands Ober‐ (0–10 cm) und Unterbodenhorizonte (ca. 50–60 cm) beprobt. Anschließend erfolgte die Bestimmung von Corgund N in den Partikelgrößen‐Fraktionen Ton (Calcic (N/V‐0.34) und Gypsic Kastanozem (N/V=0.32) zunehmend verändert. Die Corg−Gehalte sind dagegen in der Unterboden‐Feinerde des Chernozems und Phaeozems höher als im Greyzem und nehmen mit sinkenden N/V‐Quotienten (d.h. zunehmender Bodenerwärmung und ‐austrocknung) zum Calcic Kastanozem hin ab. Dies wird von einer relativen Anreicherung von Corgin der Schlufffraktion begleitet (r = −0.99 für die K

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610510

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractDas Ausmaß der Nitratauswaschung aus Böden ländlicher Siedlungsflächen ist bislang kaum erforscht. Für das ländliche Siedlungsgebiet Schwaförden bei Nienburg in Niedersachsen, das mit einem Flächenanteil von 7.5% in einem 950 ha großen Trinkwassergewinnungsgebiet liegt, wurde deshalb für eine Winterperiode der Nitrataustrag beispielhaft abgeschätzt. Dazu wurden die Bodennutzung und der nutzungsspezifische Versiegelungsgrad ermittelt und klassifiziert. In jeder Klasse wurden repräsentative Standorte während des Winters wiederholt auf Nmin beprobt. Die Nitratauswaschung wurde mit Hilfe eines Mischzellenmodells abgeschätzt. Stickstoffmineralisierung und N‐Eintrag aus der Atmosphäre wurden mitberücksichtigt. Es wurde festgestellt, daß neben den Grünflächen, die fast die Hälfte des Siedlungsgebietes einnehmen, die in den Hausgärten befindlichen Gemüsebeete einen großen Anteil an der Nitratauswaschung haben. Diese sind mit einem Flächenanteil von nur 3.5% zu circa 27% am Austrag beteiligt. Hohe Kompostgaben verbunden mit übermäßiger Mineraldüngung scheinen zu einem Stickstoffüberangebot und in der Folge zu teilweise erheblichen Reststickstoffmengen im Boden zu führen. Generell erscheint es notwendig, gemüsebaulich genutzte Flächen in Hausgärten von Siedlungen in Trinkwassergewinnungsgebieten bezüglich einer möglichen Nitratbelastung des Grundwassers mit zu berücksich

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610511

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY