Mediation of rapid electrical, metabolic, transpirational, and photosynthetic changes by factors released from wounds. I. Variation potentials and putative action potentials in intact plants

1976 ◽  
Vol 54 (23) ◽  
pp. 2642-2650 ◽  
Author(s):  
Jerome W. Van Sambeek ◽  
Barbara G. Pickard
Keyword(s):  
Action Potentials ◽  
Chemical Substance ◽  
Variation Potential ◽  
Transpiration Stream ◽  
Single Leaf ◽  
Intact Plants

Damaging representative plants from five angiosperm families by heating or crushing a small portion of a single leaf results in an electrical change which may spread throughout the shoot. In Mimosa, similar changes have previously been identified as variation potentials.Except in one of the five plants, a variation potential is often accompanied by brief fluctuations which may propagate either basipetally or acropetally and which have many of the properties of action potentials.The spread of a variation potential as described in Mimosa is due to the concommitant spread of a chemical substance in the transpiration stream. In this paper, it is shown that the spread of the purported variation potential is compatible with movement of material in the transpiration stream. In the next paper causation by a substance or group of substances, at present called Ricca's factor, is demonstrated.

Mediation of rapid electrical, metabolic, transpirational, and photosynthetic changes by factors released from wounds. II. Mediation of the variation potential by Ricca's factor

1976 ◽  
Vol 54 (23) ◽  
pp. 2651-2661 ◽  
Author(s):  
Jerome W. Van Sambeek ◽  
Barbara G. Pickard ◽  
Corinne E. Ulbright
Keyword(s):  
Plant Extract ◽  
Leaf Tissue ◽  
Variation Potential ◽  
Active Factor ◽  
Threshold Response ◽  
Transpiration Stream ◽  
Low Concentrations ◽  
The Given

An extract of Lycopersicon leaf tissue applied to the base of an excised Lycopersicon leaf causes a variation potential to spread through the leaf. This spread of an electrical wave is closely dependent on the spread of the extract via the transpiration stream, and the amplitude of the variation potential depends on the concentration of extract applied. Extract from 5–10 mg fresh leaves diluted to 1 ml elicits threshold response, and saturation is accomplished with a concentration about 40 times greater. Evidently, the active factor or factors are effective at very low concentrations. A variety of substances cause electrical disturbances when applied to the excised leaf, but plant extract is the only tested material which under the given conditions desensitizes the leaf to an application of saturating extract 5 min after the initial application.The active factor or set of factors has been extracted from plants in several families and appears to be closely related to the substance implicated by Ricca in 1916 in trauma-induced closure of Mimosa leaves. In recognition of this early discovery, the material is at present called Ricca's factor.

Mediation of rapid electrical, metabolic, transpirational, and photosynthetic changes by factors released from wounds. III. Measurements of CO2 and H2O flux

1976 ◽  
Vol 54 (23) ◽  
pp. 2662-2671 ◽  
Author(s):  
Jerome W. Van Sambeek ◽  
Barbara G. Pickard
Keyword(s):  
Net Photosynthesis ◽  
Variation Potential ◽  
Initial Burst ◽  
Intact Plants ◽  
Dark Metabolism

By using intact plants from five angiosperm families, shifts in CO2 and H2O exchange have been demonstrated to follow the arrival of a variation potential in unharmed leaves shortly after adjacent leaves are damaged.Whether in the light or dark, the first change is a brief burst of CO2, which may well be due to a sudden breakdown of bicarbonate dissolved in the extracellular solution.In the dark, a rise in metabolic CO2 output becomes evident during the decay of the initial burst, and the output remains elevated for at least several hours.In the light, a biphasic drop in both transpiration and net CO2 uptake is underway before the initial CO2 burst has subsided. Since the decrease in CO2 uptake is larger than the increase in output in the dark, it must be due in part to decreased net photosynthetic CO2 fixation. It is plausible but as yet unproven that the biphasic photosynthetic change is a consequence of the biphasic closure of the stomata. In any case, curtailment of both transpiration and net photosynthesis, like the enhancement of dark metabolism, persists for a number of hours.

Serotonergic activation of tonic-type enteric neurons in guinea pig small bowel

1979 ◽  
Vol 42 (2) ◽  
pp. 582-593 ◽  
Author(s):  
J. D. Wood ◽  
C. J. Mayer
Keyword(s):  
Action Potentials ◽  
Input Resistance ◽  
Chemical Substance ◽  
Enteric Neurons ◽  
Membrane Excitability ◽  
Fiber Tract ◽  
Fiber Tracts ◽  
Transmitter Substance ◽  
Cholinergic Agonists And Antagonists ◽  
Neurotransmitter Substance

1. Electrical stimulation of interganglionic fiber tracts of Auerbach's plexus released a chemical substance, which produced a slow EPSP associated with an increase in input resistance in the postsynaptic neuron. 2. This effect of fiber tract stimulation was mimicked by microiontophoretic application of serotonin (5-HT) to the neurons. Both the endogenous transmitter substance and exogenous 5-HT produced membrane depolarization, both increased the input resistance of the neuron, both reduced or abolished hyperpolarizing afterpotentials of the action potentials, and both augmented membrane excitability. 3. During tachyphylaxis to excess 5-HT (1 micron) in the perfusion solution, the response to fiber tract stimulation was also reversibly blocked. 4. Methysergide (30 micron) blocked both the response to fiber tract stimulation and to exogenous 5-HT. 5. Cholinergic agonists and antagonists did not alter the slow EPSP and the response to exogenous 5-HT. 6. The evidence suggests that 5-HT is the neurotransmitter substance that produces the slow EPSP in myenteric neurons.

Freeze-Fracture Studies of Membranes in Developing Sieve Elements in a Plant Tissue Culture

1980 ◽  
Vol 38 ◽  
pp. 636-637
Author(s):  
R. D. Sjolund ◽  
C. Y. Shih
Keyword(s):  
Plant Tissue ◽  
Cultured Cells ◽  
Freeze Fracture ◽  
Tissue Cultures ◽  
Sieve Elements ◽  
Intact Plants ◽  
Plant Tissue Cultures ◽  
Whole Plants ◽  
Energy Dependent ◽  
Similar Elements

The differentiation of phloem in plant tissue cultures offers a unique opportunity to study the development and structure of sieve elements in a manner that avoids the injury responses associated with the processing of similar elements in intact plants. Short segments of sieve elements formed in tissue cultures can be fixed intact while the longer strands occuring in whole plants must be cut into shorter lengths before processing. While iyuch controversy surrounds the question of phloem function in tissue cultures , sieve elements formed in these cultured cells are structurally similar to those of Intact plants. We are particullarly Interested In the structure of the plasma membrane and the peripheral ER in these cells because of their possible role in the energy-dependent active transport of sucrose into the sieve elements.

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