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451.
JOHN F. RYLEY RONALD W. GORDON J. ROGER STARK 《The Journal of eukaryotic microbiology》1974,21(4):596-598
Polysaccharides have been isolated from Eimeria bovis and E. stiedai by the use of alkali. The purified polysaccharides stain purple with iodine and have been shown by chemical and enzymic means to be amylopectin. The storage amylopectins of these coccidia differ slightly from typical plant amylopectins in their fine structure. 相似文献
452.
Ryle, G. J. A., Powell, C. E. and Gordon, A. J. 1988. Responsesof N2 fixation-linked respiration to host-plant energy statusin white clover acclimated to a controlled environment.J.exp. Bot. 39: 879887. Single plants of white clover, acclimated to a controlled environmentand dependent for nitrogen on N2 fixation in their root nodules,were darkened, defoliated or exposed to enhanced CO2 levelsto establish the quantitative relationships between the photosynthesisof the host plant and the N2 fixation metabolism of root nodules. The nodule respiration associated with N2 fixation (FLR) declinedrapidly to 1015% of its normal rate following plant darkeningearly in the photoperiod. Darkening at progressively later intervalsduring the photoperiod demonstrated a positive, apparently linearrelationship between duration of illumination and total FLRduring the photoperiod and the following night period. Completeor partial defoliation reduced FLR according to the leaf arearemoved: again, there was a strong positive correlation betweencurrent rate of photosynthesis, whether of defoliated or undefoliatedplants and the FLR of root nodules. Doubling the current rateof photosynthesis, by enhancing CO2 levels around the shoots,promoted FLR within 12 h when plants were stressed bylack of light. However, enhanced CO2 levels increased FLR onlyslowly over a period of several hours in plants entrained tothe normal growing conditions. It is concluded that, in these plants acclimated to a uniformand favourable controlled environment, the supply and utilizationof photosynthetic assimilate in N2 fixation was finely balancedand quantitatively linked during a single diurnal period andthat nodule functioning was not depressed by lack of energysubstrate. Key words: White clover, N2 fixation, photosynthesis. 相似文献
453.
GORDON J. LEITCH MARY SCANLON GOVINDA S. VISVESVARA SARA WALLACE 《The Journal of eukaryotic microbiology》1995,42(5):445-451
ABSTRACT. Microsporidia of the genus Encephalitozoon undergo merogony and sporogony in a parasitophorous vacuole within the host cell. Cultured green monkey kidney cells infected with Encephalitozoon hellem were loaded with the fluorescent dyes fura-2 or BCECF in order to measure intracellular concentrations of calcium and hydrogen ions respectively. Both the parasitophorous vacuole calcium concentration and pH values resembled those of the host cell cytoplasm in infected cells. Calcein entered the parasitophorous vacuole but not other host cell vacuoles or parasite stages within the parasitophorous vacuole. The lack of a pH or calcium concentration gradient across the parasitophorous vacuole membrane and the permeability of this membrane to a large anion such as calcein suggest that the vacuole membrane surrounding E. hellem resembles that surrounding some other intracellular parasites such as Toxoplasma gondii. A potential role is discussed for the parasitophorous vacuole calcium concentration in germination in situ. 相似文献
454.
SHERWIN HEATHER W.; PAMMENTER N. W.; FEBRUARY ED; VANDER WILLIGEN CLARE; FARRANT JILL M. 《Annals of botany》1998,81(4):567-575
Myrothamnus flabellifoliusWelw. is a desiccation-tolerant (resurrection)plant with a woody stem. Xylem vessels are narrow (14 µmmean diameter) and perforation plates are reticulate. This leadsto specific and leaf specific hydraulic conductivities thatare amongst the lowest recorded for angiosperms (ks0.87 kg m-1MPa-1s-1;kl3.28x10-5kg m-1MPa-1s-1, stem diameter 3 mm). Hydraulic conductivitiesdecrease with increasing pressure gradient. Transpiration ratesin well watered plants were moderate to low, generating xylemwater potentials of -1 to -2 MPa. Acoustic emissions indicatedextensive cavitation events that were initiated at xylem waterpotentials of -2 to -3 MPa. The desiccation-tolerant natureof the tissue permits this species to survive this interruptionof the water supply. On rewatering the roots pressures thatwere developed were low (2.4 kPa). However capillary forceswere demonstrated to be adequate to account for the refillingof xylem vessels and re-establishment of hydraulic continuityeven when water was under a tension of -8 kPa. During dehydrationand rehydration cycles stems showed considerable shrinking andswelling. Unusual knob-like structures of unknown chemical compositionwere observed on the outer surface of xylem vessels. These maybe related to the ability of the stem to withstand the mechanicalstresses associated with this shrinkage and swelling.Copyright1998 Annals of Botany Company cavitation, desiccation, hydraulic conductivity, refilling, resurrection plant, root pressure, xylem anatomy,Myrothamnus flabellifolius 相似文献
455.
Plasmodesmata, Tropisms, and Auxin Transport 总被引:4,自引:0,他引:4
Attempts were made to disrupt the plasmodesmata between oatcoleoptile cells (Avena saliva L. cv. Victory) by severe plasmolysis.Coleoptiles, allowed to regain turgor after plasmolysis, wereable to execute geotropic and phototropic curvatures and segmentswould grow in response to applied auxin. In coleoptiles similarlytreated, studies with [14C]IAA have shown that longitudinal,basipetal transport of auxin still takes place and, as in controls,IAA is preferentially redistributed laterally within coleoptilesorientated horizontally. Physical continuity of the symplast of oat coleoptile cellsmay not always be disrupted by severe plasmolysis. Nevertheless,functional continuity appears to be interrupted. Despite this,all the processes involved in the execution of tropistic curvaturesremain intact, including transport of hormones. Plasmodesmatalcontinuity between oat coleoptile cells appears not to be anecessary requirement for auxin transport. 相似文献
456.
Recovery of learning responses by honeybees following a sublethal exposure to permethrin 总被引:1,自引:0,他引:1
ABSTRACT A classical conditioned response was used to evaluate the learning behaviour of honeybees ( Apis mellifera L.) which survived a sublethal dose of permethrin. Treated bees had lower learning response levels than untreated bees for 3 days, but regained normal learning ability on the fourth day after exposure. However, bees trained prior to exposure showed no significant effect of permethrin on their conditioned response. 相似文献
457.
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460.
GORDON JJ 《The Biochemical journal》1953,55(5):812-817