Abstract
Sunflower plants ( Helianthus annuus L.) were given an electrical stimulus to the stem or a heat (flame)‐wound to a single leaf or a cotyledon. The resulting electrical activity was monitored with extracellular electrodes. An electrical stimulus applied to the stem frequently evoked an action potential (AP), but never a variation potential (VP). In contrast, a heat‐wound applied to a leaf virtually always elicited a VP, which was often accompanied by one or more superimposed spikes (putative APs). The kinetic parameters of the AP and the VP were investigated. The AP appears to propagate without decrement in velocity or magnitude, whereas the VP parameters decrease significantly with distance. The heat stimulus triggered rapid alterations in stem elongation/contraction, which preceded changes in electrical potential, indicating the transmission of a hydraulic signal. Light‐off and light‐on stimuli evoked negative‐ and positive‐going changes in extracellular electrical potential, respectively, corresponding to de‐ and hyper‐polarization of the plasma membrane. Membrane depolarization (extracellularly manifested as a VP) evoked by both the light‐off and heat‐wounding stimuli was able to trigger one or more APs. We interpret these results to suggest that APs are “genuine” electrical signals involving voltage‐gated ion channels or pumps, which can be evoked directly by electrical stimulation or indirectly by changes in membrane potential occurring during the VP or after the light‐off stimulus. In contrast, VPs appear to be a local (non‐transmissible) electrical consequence of the passage of a rapidly transmitted hydraulic signal in the xylem, presumably acting on mechanosensitive ion channels or pumps in adjacent living cells.
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Claims 13
Claim · model-written summary
Electrical stimulation of the stem frequently evoked action potentials.
- Taxon
- sunflower
Helianthus annuust0 - Treatment
- An electrical stimulus applied to the steme0
- Outcome
- an action potential (AP)e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“An electrical stimulus applied to the stem frequently evoked an action potential (AP), but never a variation potential (VP).”
t0“sunflower”
Claim · model-written summary
Electrical stimulation of the stem never evoked variation potentials.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- An electrical stimulus applied to the steme0
- Outcome
- never a variation potential (VP)e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“An electrical stimulus applied to the stem frequently evoked an action potential (AP), but never a variation potential (VP).”
t0“sunflower”
Claim · model-written summary
Heat wounding a leaf virtually always elicited a variation potential.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- a heat‐wound applied to a leafe0
- Outcome
- a VPe0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a heat‐wound applied to a leaf virtually always elicited a VP, which was often accompanied by one or more superimposed spikes (putative APs).”
t0“sunflower”
Claim · model-written summary
Heat-wound variation potentials were often accompanied by spikes.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- a heat‐wound applied to a leafe0
- Outcome
- one or more superimposed spikes (putative APs)e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a heat‐wound applied to a leaf virtually always elicited a VP, which was often accompanied by one or more superimposed spikes (putative APs).”
t0“sunflower”
Claim · model-written summary
Action potentials appeared to propagate without decrement in velocity or magnitude.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- velocity or magnitudee0
- Direction
- without decremente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The AP appears to propagate without decrement in velocity or magnitude, whereas the VP parameters decrease significantly with distance.”
t0“sunflower”
Claim · model-written summary
Variation potential parameters decreased significantly with distance.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- VP parameterse0
- Direction
- decreasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The AP appears to propagate without decrement in velocity or magnitude, whereas the VP parameters decrease significantly with distance.”
t0“sunflower”
Claim · model-written summary
Heat stimulus rapidly altered stem elongation or contraction before electrical potential changed.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- The heat stimuluse0
- Outcome
- rapid alterations in stem elongation/contractione0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The heat stimulus triggered rapid alterations in stem elongation/contraction, which preceded changes in electrical potential, indicating the transmission of a hydraulic signal.”
t0“sunflower”
Claim · model-written summary
Light-off evoked negative-going extracellular potential changes.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- Light‐offe0
- Outcome
- negative‐ and positive‐going changes in extracellular electrical potentiale0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Light‐off and light‐on stimuli evoked negative‐ and positive‐going changes in extracellular electrical potential, respectively, corresponding to de‐ and hyper‐polarization of the plasma membrane.”
t0“sunflower”
Claim · model-written summary
Light-on evoked positive-going extracellular potential changes.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- light‐one0
- Outcome
- negative‐ and positive‐going changes in extracellular electrical potentiale0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Light‐off and light‐on stimuli evoked negative‐ and positive‐going changes in extracellular electrical potential, respectively, corresponding to de‐ and hyper‐polarization of the plasma membrane.”
t0“sunflower”
Claim · model-written summary
Light-off-induced membrane depolarization triggered action potentials.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- light‐offe0
- Outcome
- one or more APse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Membrane depolarization (extracellularly manifested as a VP) evoked by both the light‐off and heat‐wounding stimuli was able to trigger one or more APs.”
t0“sunflower”
Claim · model-written summary
Heat-wound-induced membrane depolarization triggered action potentials.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- heat‐woundinge0
- Outcome
- one or more APse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Membrane depolarization (extracellularly manifested as a VP) evoked by both the light‐off and heat‐wounding stimuli was able to trigger one or more APs.”
t0“sunflower”
Claim · model-written summary
The authors interpret action potentials as electrical signals involving voltage-gated channels or pumps.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- electrical signals involving voltage‐gated ion channels or pumpse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“APs are “genuine” electrical signals involving voltage‐gated ion channels or pumps”
t0“sunflower”
Claim · model-written summary
The authors interpret variation potentials as local consequences of a transmitted xylem hydraulic signal.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- a local (non‐transmissible) electrical consequence of the passage of a rapidly transmitted hydraulic signal in the xyleme0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“VPs appear to be a local (non‐transmissible) electrical consequence of the passage of a rapidly transmitted hydraulic signal in the xylem”
t0“sunflower”