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91.
Extension of the phosphorus depletion zone in VA-mycorrhizal white clover in a calcareous soil 总被引:23,自引:2,他引:21
To examine the influence of vesicular-arbuscular (VA) mycorrhizal fungi on phosphorus (P) depletion in the rhizosphere, mycorrhizal
and non-mycorrhizal white clover (Trifolium repens L.) were grown for seven weeks in a sterilized calcareous soil in pots with three compartments, a central one for root growth
and two outer ones for hyphae growth. Compartmentation was accomplished by a 30-μm nylon net. The root compartment received
a uniform level of P (50 mg kg−1 soil) in combination with low or high levels of P (50 or 150 mg kg−1 soil) in the hyphal compartments. Plants were inoculated withGlomus mosseae (Nicol. & Gerd.) Gerd. & Trappe or remained uninfected.
Mycorrhizal inoculation doubled P concentration in shoot and root, and increased dry weight, especially of the shoot, irrespective
of P levels. Mycorrhizal contribution accounted for 76% of total P uptake at the low P level and 79% at the high P level,
and almost all of this P was delivered by the hyphae from the outer compartment. In the non-mycorrhizal plants, the depletion
of NaHCO3-extractable P (Olsen-P) extended about 1 cm into the outer compartment, but in the mycorrhizal plants a uniform P depletion
zone extended up to 11.7 cm (the length of the hyphal compartment) from the root surface. In the outer compartment, the mycorrhizal
hyphae length density was high (2.5–7 m cm−3 soil) at the various distances (0–11.7 cm) from the root surface. Uptake rate of P by mycorrhizal hyphae was in the range
of 3.3–4.3×10−15 mol s−1 cm−1. 相似文献
92.
S. R. Rodriguez de Cianzio 《Plant and Soil》1991,130(1-2):63-68
Iron-chlorosis deficiency may occur when an iron-inefficient genotype is grown on calcareous soil. One way to correct the problem is to modify the genotype by plant breeding. Cultivars have been released for oat (Avena byzantina C. Koch), sorghum [Sorghum bicolor (L.) Moench], dry bean (Phaseoulus vulgaris L.), and soybean [Glycine max (L.) Merr.]. Progress is being made in peanut (Arachis hypogea L.), forage species such as clovers (Trifolium sp.) and bluestems (Botriochloa sp.), and pepper (Capsicum annuum L.). Screening of rootstocks is done on citrus (Citrus sp.), mango (Manguifera indica L.), and avocado (Persea americana Mill.). 相似文献
93.
It has been shown previously (Treeby et al., 1989) that phytosiderophores, released by roots of iron deficient grasses (Gramineae), mobilize from calcareous soils not only iron (Fe) but also zinc (Zn), manganese (Mn) and copper (Cu). Mobilization of Fe may therefore be impaired by other micronutrient cations. This has been studied in both, model experiments with Fe hydroxide and with a calcareous soil (15% CaCO3, pH 8.6) amended with micronutrients as sulfate salts.Mobilization of Fe from Fe hydroxide by phytosiderophores (epi-3-hydroxymugineic acid) was not affected by the addition of CaCl2, MgSO4 and MnSO4, slightly inhibited by ZnSO4 and strongly inhibited by CuSO4. In a calcareous soil amended with increasing levels of ZnSO4, MnSO4 and CuSO4, mobilization of Fe by phytosiderophores remained uneffected by Zn and Mn amendments but was progressively impaired by increasing levels of Cu amendment, correlated with corresponding enhancement of Cu mobilization.High concentrations of ZnSO4 and MnSO4 and relatively high concentrations of CuSO4 were required for inhibition of Fe mobilization by phytosiderophores. It is therefore concluded that in most calcareous soils phytosiderophores efficiently mobilize Fe, and that phytosiderophores play an important role in Fe acquisition by grasses grown on calcareous soils. 相似文献
94.
细粒棘球绦虫原头蚴组织化学的观察 总被引:3,自引:0,他引:3
本文对细粒棘球绦虫原头蚴的组织化学成份进行了较为系统和全面的观察,结果表明,该虫体内存在糖原、RNA、DNA、蛋白质结合的α-氨基、酪氨酸、色氨酸及组氨酸、碱性蛋白质、酸性粘多糖、胶原及网状纤维成分、AKP、ATP酶及ACP等生化物质。并对上述成分的定位,含量及其生理学的意义进行了重点讨论。 相似文献
95.
Erica M Crouch Gerald R Dickens Henk BrinkhuisMarie-Pierre Aubry Christopher J HollisKaryne M Rogers Henk Visscher 《Palaeogeography, Palaeoclimatology, Palaeoecology》2003,194(4):387-403
Manifestations of profound perturbations in biogeochemical systems during the Paleocene-Eocene thermal maximum (PETM) include a prominent global negative δ13C and a pronounced increase in the relative abundance of dinoflagellate cysts (dinocysts) assigned to the genus Apectodinium. While motile representatives of Apectodinium were most likely thermophilic and heterotrophic, the underlying causes of this dinoflagellate response are not well understood. Here we provide new insight by examining the palynology, chemistry and calcareous nannoplankton across the PETM in a continental slope section at Tawanui, New Zealand. Across the PETM, marked changes in the relative abundance of Apectodinium vary antithetically with significant changes in the δ13C of carbonate and organic matter. In general, the high relative abundance of Apectodinium relates to enhanced concentrations of dinocysts, signifying a ‘bloom’ of Apectodinium in surface waters during the PETM. Changes in Apectodinium and δ13C records correspond to variations in many other parameters, including a smaller negative shift in bulk carbonate δ13C than expected, increased terrestrial palynomorphs, elevated TOC and C/N ratios, lower carbonate contents, higher SiO2 and Al2O3 contents, and lower Si/Al ratios. All of these variations can be explained by an increase in delivery of terrigenous material to the continental margin. A peak in the relative abundance of Glaphyrocysta dinocysts at the onset of the PETM may indicate greater down slope transport of neritic material. Changes in calcareous nannoplankton abundances suggest increased nutrient availability in surface waters during the PETM. The combined results show that Apectodinium-dominated assemblages, global perturbations in carbon isotopes and enhanced terrigenous delivery closely correspond in time at Tawanui. A sudden and massive carbon injection to the ocean-atmosphere system may have enhanced weathering and increased terrigenous inputs to continental margins during the PETM. We further suggest that these inputs caused the Apectodinium acme by elevating primary productivity in marginal seas. 相似文献
96.
接种AM真菌对玉米和油菜种间竞争及土壤无机磷组分的影响 总被引:7,自引:0,他引:7
在温室盆栽条件下,分别模拟单作、间作和尼龙网分隔种植,比较接种丛枝菌根(arbuscular mycorrhizal, AM)真菌Glomus intraradices和Glomus mosseae对菌根植物玉米和非菌根植物油菜生长和磷吸收状况的影响,并分析土壤中各无机磷组分的变化。结果发现,接种AM真菌可以促进土壤中难溶性磷(Ca10-P和O-P)向有效态磷转化,并显著降低总无机磷含量 (P<0.05),显著提高菌根植物玉米的生物量和磷吸收量(P<0.05),特别是在间作体系中使玉米的磷营养竞争比率显著提高了45.0%-104.1% (P<0.05),显著降低了油菜的生物量和磷吸收量(P<0.05),从而增强了了菌根植物的竞争优势,降低了非菌根植物与菌根植物的共存能力。揭示了石灰性土壤中AM真菌对植物物种多样性的影响,有助于更加全面地理解AM真菌在农业生态系统中的作用。 相似文献
97.
98.
Elisa Guasti Robert P. Speijer Henk Brinkhuis Jan Smit Etienne Steurbaut 《Marine Micropaleontology》2006,59(3-4):210-229
In the present study, we document paleoenvironmental change across the Danian–Selandian transition (planktic foraminiferal interval P2–P3b; calcareous nannofossil Zone NP4, Subzones NTp6–NTp8A; 61–59 Ma) in NW Tunisia. Diversifications of Paleogene planktic foraminifera with the evolution of the muricate and photosymbiotic lineages Morozovella, Acarinina and Igorina and of the biostratigraphically important nannofossils genus Fasciculithus are recorded within this interval. The present study aims to understand early Paleogene environmental changes in the southern Tethys, by analyzing the evolution of surface-water and–to a lesser extent–seafloor conditions. Three localities were investigated: Ain Settara, Elles and El Kef, all representing outer neritic deposition in the same basin, the Tunisian Trough. Paleoenvironmental changes are explored by combining planktic foraminiferal, organic dinocyst and calcareous nannofossils assemblages and several proxy parameters (planktic/benthic ratio, numbers of planktic foraminifera per gram, peridinioid/gonyaulacoid ratio; terrestrial/marine palynomorph ratio). In addition, also some geochemical parameters (calcite content and stable isotopes) are examined. Our records indicate that the environment evolved from an initially oligotrophic, open marine, deep outer neritic setting in P2–P3a towards a shallower and nutrient-rich setting from the base of Subzone P3b. This change is seen in the foraminiferal assemblages, with the substitution of Praemurica by Morozovella among the planktic foraminifera and an upward decrease in deeper benthic taxa. Also the organic-dinocyst assemblages show a peak of peridinioid cysts (Cerodinium and Lejeunecysta). Associated to these dinocyst assemblages, the lowest occurrence of Apectodinium is recorded, which seem to have evolved in this region, possibly in response to enhanced nutrient levels on the shelf. Additionally, a distinct change in calcareous nannofossil assemblages is also described, marked by the lowest appearance of Chiasmolithus edentulus, the lowest consistent occurrence of Fasciculithus and a slight increase in near-shore taxa (essentially Pontosphaera).This project provides an accurate understanding of paleoenvironmental change across the Danian–Selandian transition in Tunisia. Especially, integrating different proxies demonstrates a paleobathymetric shallowing from the Danian to the Selandian, associated to increase surface paleoproductivity. Furthermore, the results are compared with those from other localities along the Southern Tethyan margin (Egypt and Jordan) and a more regional paleoclimatic/paleoceanographic perturbation in the Southern Tethys is suggested. 相似文献
99.
by GERARD J. M. VERSTEEGH† THOMAS SERVAIS MICHAEL STRENG‡ AXEL MUNNECKE§ DANIEL VACHARD 《Palaeontology》2009,52(2):343-348
Abstract: The terminology and grouping of spherical, calcareous microfossils of unknown biological affinity, usually referred to as calcispheres, are diffuse. The term calcispheres is inconsistently used, the morphological and taxonomical concepts are mostly ill-defined and a formal definition is lacking. To resolve this issue, we propose, in analogy with the erection of the Acritarcha for organic microfossils of unknown origin, a new group called Calcitarcha, including all calcareous microfossils with a central cavity for which the biological affinities remain unknown. 相似文献
100.
V. A. Luchinina 《Paleontological Journal》2009,43(4):463-468
Although the calcareous algae Renalcis and Epiphyton, which were main reef-constructors at the end of the Late Proterozoic, beginning of the Cambrian, and, partially, in the Devonian, long attracted the attention of scientists, their nature long remained enigmatic. Numerous revisions inclined to the opinion that Renalcis only existed and considered Chabakovia, Shuguria, Izhella, and even Epiphyton as synonyms of the former genus. However, convincing proofs for this conclusion were lacking. I propose a new morphological interpretation of the Renalcis group, based on Gemma with its unique preservation of monospores within the colony, which overgrew outside the colony first in Korilophyton and then in Epiphyton. It was concluded that the life cycle of Epiphyton included heteromorphous stages of Renalcis (Izhella), Chabakovia (Shuguria), Gemma, and dendroid Korilophyton. 相似文献