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101.
102.
Nitrogen assimilation in Lolium perenne colonized by the arbuscular mycorrhizal fungus Glomus fasciculatum 总被引:1,自引:0,他引:1
SANDRINE FAURE JEAN-BERNARD CLIQUET GAELLE THEPHANY & JEAN BOUCAUD 《The New phytologist》1998,138(3):411-417
To investigate nitrogen assimilation in Lolium perenne L. colonized by the arbuscular mycorrhizal (AM) fungus Glomus fasciculatum (Thax. sensu Gerd.), nitrate uptake, key enzyme activities, and 15 N incorporation into free amino acids were measured. After a 4-h labelling period with [15 N]nitrate, 15 N content was higher in roots and shoots of AM-plants than in those of control plants. Glutamine synthetase (GS) and nitrate reductase (NR) activities were increased in shoots of AM-plants, but not in roots. More label was incorporated into amino acids in shoots of AM plants. Glutamine, glutamate, alanine and γ-aminobutyric acid were the major sinks for 15 N in roots and shoots of control and AM plants. Interactions between mycorrhizal colonization, phosphate and nitrate nutrition and NR activity were investigated in plants which received different amounts of phosphate or nitrate. In shoots of control plants, NR activity was not stimulated by high levels of phosphate nutrition but was stimulated by high levels of nitrate. At 4 m M nitrate in the nutrient solution, NR activity was similar in control and AM plants. We concluded that mycorrhizal effects on nitrate assimilation are not mediated via improved phosphate nutrition, but could be due to improved nitrogen uptake and translocation. 相似文献
103.
JEAN GALTIER SHI-JUN WANG CHENG-SEN LI JASON HILTON † 《Botanical journal of the Linnean Society. Linnean Society of London》2001,137(4):429-442
Recent investigation on the Cathaysian flora of the Lower Permian Taiyuan Formation in Hebei Province, North China has led to the discovery of a new type of fern, Rastropteris pingquanensis gen. et sp. nov. Preserved as a permineralization, the stem, with a mantle of petiole bases and roots, shows a unique combination of anatomical characters. The vascular strand consists of a solid protostele with uniformly elongated tracheids and mesarch maturation of the xylem. In transverse section, the configuration of leaf trace xylem changes from reniform endarch to a tangentially elongated strand adaxially recurved at each end with several adaxial ridges. Stem and petiole cortex contains abundant sclerotic tissue with an interstitial tissue developed within the mantle of petiole bases and roots. A reinvestigation of Grammatopteris rigollotii , from the Permian of France, the type species of the genus allows interpretation of the latter as closer to Rastropteris than any other fern. Both taxa are provisionally reported to an incertae sedis group of filicalean ferns possibly involved in the origin of Osmundaceae. 相似文献
104.
VINCENT PERRIER JEAN VANNIER PATRICK R. RACHEBOEUF† SYLVAIN CHARBONNIER DOMINIQUE CHABARD‡ DANIEL SOTTY‡ 《Palaeontology》2006,49(3):647-672
Abstract: Key aspects of the morphology, autecology, systematics and taphonomy of the crustacean syncarids from the Montceau Lagerstätte (Upper Carboniferous, Stephanian B; France) are presented. Palaeocaris secretanae is the most abundant faunal element of the Montceau biota and shows striking morphological similarities with Palaeocaris typus from the Mazon Creek Lagerstätte (Westphalian D; Illinois, USA). Palaeocaris secretanae was a shrimp‐like animal with a short head (no head shield), large mandibles, 14 trunk segments (the first one being reduced) and a fan‐like caudal termination. Both the body and the appendage design indicate abilities for crawling on the substratum (slender endopods) and for escape reaction (uropodal fan, pleonal flexibility), although swimming activities may have been reduced (trunk appendages with small flap‐like exopods). Details of the appendages involved in feeding, e.g. mandibles and maxillipeds, indicate poor ability for predation but point to an omnivorous detritus feeding mode. Poorly developed respiratory organs (small cylindrical epipods) suggest a relatively low level of locomotory activity. The field of vision may have been large and panoramic (stalked eyes). Rows of pores on 12 trunk segments are interpreted as possible sensory organs used for current detection. Females were brooding eggs (clusters of eggs preserved along anteroventral trunk). Microprobe analysis indicates that siderite is the major component of the nodules. Four events played a key‐role in the three‐dimensional preservation of syncarids: (1) rapid burial, (2) minimal decomposition, (3) phosphatic mineralization shortly after the animal's death and (4) nodule formation around the carcass. Palaeocaris secretanae is morphologically close to Recent syncarids such Anaspides tasmaniae (freshwater streams, Australia) in its general body plan and detailed anatomy, e.g. mouth parts, indicating morphological stasis in syncarids over more than 200 million years. 相似文献
105.
Calluses and cell suspension cultures were initiated from young and fully developed fruits and from stem and petiole tissues of ‘Passe Crassane’ pears. On a dry weight basis, proliferation is significantly higher in tissues from full-grown fruits and petioles. Cullus tissues grown in vitro have a protein content up to 25 times higher than the initial quiescent organ. Three amylase fractions (2 β amylases E, and E2: 1 α amylase E3) were isolated by gel filtration on Sephadcx G-100 and isoenzymes revealed in these fractions after polyacrylamide gel electrophoresis. Comparison of amylase activity in actively growing cells and in auxin-starved cell suspensions shows that β-amylase activity is mainly a function of cell growth, while α-amylase activity is more related to the age of the cells. The presence of two isoenzymes in the β-amylase E2 fraction was found to be highly characteristic of young fruits. The same polymorphism was found in all the strain of tissues thus indicating that tissues grown in vitro retain or revert to a juvenile biochemistry. The growth hormone. 2,4-dichlorophenoxyacetic acid, used to support cell division, is demonstrated to be responsible for the reversion of the β-amylase polymorphism from a mature to a juvenile phenotype in mature fruit explants incubated in vitro. The interest of fruit tissue and cell culture for the study of fruit physiology is questioned and discussed. 相似文献
106.
Leaves of Phaseolus vulgaris L. contained malate dehydrogenase activity dependent on NADP (E. C. 1.1.1.82); it could be detected in extracts only when a dithiol such as dithiothreitol was present. After the addition of dithiothreitol, the activity increased with time, passed through a maximum and then diminished. The activation rate and/or the maximum level of activity were essentially dependent on dithiothreitol concentration, pH, and temperature. The presence of bovine serum albumine or glycerol in the medium decreased the inactivation rate; equivalent results were obtained at low temperatures. A mathematical model was established showing an apparent first-order rate for activation and inactivation only under conditions of alkaline pH near 8.3. These data allowed us to demonstrate that compounds other than dithiothreitol were necessary for the activation process. Evidence suggested that these compounds were protein factors of low molecular weights which increased the activation rate and the maximum level of activity when added to the incubation medium at pH 7.3. Their efficiency in the enzyme activation was higher at alkaline pH than at acid or neutral pH. 相似文献
107.
BY ALEXANDER H. PURCELL JEAN RICHARDSON ALLAN FINLAY 《The Annals of applied biology》1981,99(3):283-289
The relative titre of the causal agent of X-disease of stone fruits in the non-vector leafhopper Macrosteles fascifrons was tested by injecting dilutions of M. fascifrons extracts into non-infective Colladonus montanus leafhopper vectors. The recipient C. montanus were fed on celery test plants which were then observed for X-disease symptoms. M. fascifrons were assayed at various intervals for up to 37 days after they were fed on X-diseased celery or injected with infectious extracts of the X-agent. Infectivity was detected in M. fascifrons only after 25 or 37 days in separate trials. Whole body extracts but not extracts from detached heads of M. fascifrons that had fed on X-diseased celery were infectious, whereas extracts prepared from the heads of M. fascifrons previously injected with X-agent extracts were infectious. This infectivity was retained for up to four serial passages in M. fascifrons. Electron microscopy of M. fascifrons that had been injected with extracts of the X-disease agent revealed mycoplasma-like organisms (MLO) only intercellularly and appressed to various organs in the haemocoele. No MLO were observed in uninjected M. fascifrons or those injected with extracts from non-infectious C. montanus. These results suggest that, despite multiplication of the X-agent in vivo. barriers in the gut and salivary glands prevent its transmission to plants by M. fascifrons. 相似文献
108.
JEAN BOUCAUD 《Physiologia plantarum》1972,27(1):37-42
The nitrate reductase activity of Suaeda maritima var. macrocarpa and var. flexilis grown on nitrate-rich substrates with 1 to 23 g/1 NaCl is maximum after 30 days of culturing. Compared to the substrate with the lowest salt content, the activity increase obtained with 7.5 g/1 of NaCl is greater in the more halophilous variety (var. macrocarpa). Even though the NaCl docs not operate directly on the induction and activity of nitrate reductase, it is responsible for this increase by modifying the CO2 assimilation and protein synthesis. 相似文献
109.
During the ponding of Sitka spruce in lake water there was a change from a diverse, aerobic flora (16 species) to a restricted, facultatively anaerobic flora (1 or 2 species). This change corresponded with a marked increase in the degradation of pectin and a concomitant increase in the permeability of the wood to preservatives. A strain of Enterobacter cloacae (NCPPB 2909) isolated during ponding, synthesized an extracellular and intracellular polygalacturonase (PG) and an intracellular polygalacturonate trans-eliminase (PGTE). Both PG and PGTE were growth–linked; extracellular PG was produced initially and then replaced by intracellular PG and PGTE. A change in the pH value of the medium did not alter the relative synthesis of enzyme. Reduced oxygen tension retarded growth but had no effect on enzyme activities. PG and PGTE of E. cloacae were shown to have specific ion requirements and when tap-water was used in the preparation of a medium growth did not occur. The results are discussed in relation to an artificial system of sprinkling water, seeded with known species of bacteria, on to spruce wood in order to control the rate of pectin degradation and thus the permeability of the wood to preservatives. 相似文献
110.
RAMBAUD CAROLINE; BLERVACQ ANNE-SOPHIE; DEVAUX PIERRE; DUBOIS THERESE; DUBOIS JEAN; LAMMIN FRANCOIS; VASSEUR JACQUES 《Annals of botany》1996,78(2):223-232
Several papers dealing with carrot cell cultures describe meiosis-likedivisions and haploid cells prior to somatic embryogenesis.We have studied the first division in embryogenic mesophyllcells of a diploidCichorium intybus L. and of a tetraploid hybridC.intybus L.xC. endivia L. which undergo direct somatic embryogenesisfrom single cells when leaf fragments are placed in a liquidagitated inductive medium (modified MS with 1x10-7M NAA and2.5x10-6M 2-iP), in darkness, at 35°C. MicrosporogenesisinC. intybus provided aspects of meiosis for comparison. Inleaves incubated in inductive conditions, DAPI staining of nucleishowed normal mitosis on days 36; about 0.6% cells inprophase had undergone spontaneous endoreduplication leadingto a tetraploid somatic embryo. Immunocytochemistry of tubulinrevealed the constant presence of a preprophase band, as ina normal mitosis. The first pluricellular somatic embryos becamevisible on day 5 of culture. Flow cytometric determination ofnuclear DNA on days 4, 5 and 6 did not show any peak correspondingto the 1C DNA level for the diploid plant or to the 2C DNA levelfor the tetraploid. Instead there was a weak but constant peakat the 4C and 8C levels. We conclude that inCichorium leaves,the first division of somatic embryogenesis is a normal mitosis,with a small shift to endoreduplication. In our opinion, somaticmeiosis is not a prerequisite during direct somatic embryogenesis. Cichorium ; chicory; somatic embryogenesis; cell division; flow cytometry; tubulin 相似文献