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The refractory periods for action potentials (AP) were investigatedin Lupinus shoots by application of pairs of electrical stimuli(d.c). The response (AP) for the second stimulus is characterized.The second response differs in amplitude, range, and propagationvelocity from the first, depending on the strength of the stimuliand the time interval between them. The absolute refractoryperiod determined on this basis lasts 12 min, and the relativeone from 12 to about 90 min. The character of the refractoryphenomenon is similar in the case of nerves, only the processesin Lupinus are 103 to 105 times slower. The possibility of transmission of excitation from cell to cellis discussed. 相似文献
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Transnodal Transport of 14C in Nitella flexilis: I. TANDEM CELLS WITHOUT APPLIED PRESSURE GRADIENTS 总被引:1,自引:0,他引:1
Using NaH14CO3 (0·01-0·03 mol m3) fed to5·0 mm of Nitella flexilis in artificial pond water at2225°C, we have found that uptake in 5 min or in1 h varies with the streaming rate of the fed cell and is reducedby anoxia over the uptake position. We have also found thatthe %14C transported across the node between two internodalcells in tandem is highly sensitive to the streaming rate ineach cell, to the physiological state of the cells (summer versuswinter), to the method of feeding (5 min versus 1 h) and tocovering the node, particularly with winter cells or summercells preconditioned for 3 h in the dark and run in the dark.Transnodal transport by plasmodesmata is sensitive to anoxiaand seems to be at least partly active. Key words: Node, plasmodesmata, anoxia, active transport, influx 相似文献
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Using carefully standardized test conditions and tandem pairsof cells of Nitella flexilis, the influx of 14C (added as H14CO3and transnodal transport were studied under various pressuregradients applied across the node up to P=± 2·5bar. When mannitol was used as the osmoticum, influx was foundto increase only when the mannitol solution was around the cellproximal to the feed. 14C was transported across the node tothe distal cell, probably as 14C-photosynthate products, evenagainst a pressure gradient of 2 bars or more, as was 36Cland 32P. The % transported in general decreased with increasingP, whether assisted or opposed by added pressure. It was unchangedby the presence of mannitol at the node and was essentiallythe same whether the pressure gradient was produced by directpressure or by use of the osmoticum. Transnodal transport of14C products is almost certainly via plasmodesmata and appearsto be largely by an active mechanism. In absolute amounts itis the same whether the pressure gradient assists or opposesflow. Valving is evident at the node, increasing the resistanceto transport as the pressure gradient increases whether 14C(asHCO3), 42K+ (as KCl), 36Cl (as NaCl) or 32P (asNa3PO4) are used to detect it. The mechanism of movement ofK+ across the node differs from that of photosynthate products. Key words: Node, plasmodesmata, pressure gradients, active transport 相似文献
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In Lupinus shoots an electrical stimulus (d.c.) produces a potentialwave analogous to the action potential wave (AP) in stimulatedsimple plant cells or in nerves. The method used (Paszewskiand Zawadzki, 1973a, b) is similar to those applied in neurophysiologyin research on the excitability of nerves. In the present paper the strength-duration relation (Eqn. (1))of the excitation in Lupinusitalic has been used to calculatethe values of the rheobase, chronaxie, and useful time of pulse.The rheobase, as a threshold value of the stimulus, is examinedin terms of the applicability of the all-or-nothing law. The results suggest that the origin and propagation of AP inplants and in nerves may occur in a similar way. The analogybetween the impulse propagation in nerve trunks and in Lupinusshoots is discussed. 相似文献
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The character of action potentials induced by thermal or electricalstimulation and their blocking by removal of a ring of tissuefrom the shoot as well as the spread of these potentials inthe Lupinus shoot were investigated. The appearance of anothertype of excitation was noted as a graded response occurringlocally. This potential was termed graded potential (GP). Itappears in tissues in which action potentials (AP) are not observed. It is proposed that two interrelated types of reaction to stimulioccur in various types of plant tissue. 相似文献
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ZAWADZKI ZA 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1954,9(8):246-9; contd
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