Abstract
The effect of leaf desiccation on the photosynthetic activities in vivo was probed by the photoacoustic method. The aim of this research was: (a) To study the photoacoustic signal per se in varied conditions in order to develop this tool as a probe for stress conditions in vivo. (b) To obtain results pertaining to electron transport activities in vivo, and confirm conclusions based on work with isolated chloroplasts, which could otherwise be the result of nonspecific damage occurring during their isolation. Leaf discs from tobacco (Nicotiana tabacum L.) were routinely used, with other species tested also for comparison. Rapid leaf desiccation caused changes in the low frequency photoacoustic signal, attributed both to the mechanism of signal transduction, influenced by changes in the structural parameters of the leaf, and to the direct (nonstomatal) inhibition of gross photosynthesis. The dependence of the photothermal part of the signal on the frequency indicated the presence of two photothermal components, one of which persisted only at low modulation frequencies (below about 100 Hz) and which largely increased with the desiccation treatment. This component was ascribed to a thermal wave which reaches the leaf surface. The other nonvariable photothermal component was ascribed to a thermal wave propagating from the chloroplasts to the surface of the mesophyll cell. Only this component is considered in the ratio of the O(2) signal to the photothermal signal, which is used to estimate the quantum yield of photosynthesis. The specific dependence of the latter ratio on the frequency yielded a comparative quantum yield parameter from its extrapolation to zero frequency, and also indicated stress induced changes in the diffusion of O(2) through the mesophyll cell, reflected by changes in its characteristic slope. The (zero frequency extrapolated) quantum yield was markedly reduced with the progression of the water stress, indicating the inhibition of (gross) phototosynthetic electron transport in vivo. This result was expressed even more emphatically by the stronger inhibition of the photochemical energy storage, obtained by photoacoustic measurements at a high modulation frequency.
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Claims 8
Claim · model-written summary
Rapid leaf desiccation changed low frequency photoacoustic signals.
- Taxon
- tobacco (Nicotiana tabacum L.)
Nicotiana tabacume1 - Treatment
- Rapid leaf desiccatione0
- Outcome
- low frequency photoacoustic signale0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rapid leaf desiccation caused changes in the low frequency photoacoustic signal”
e1“tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Rapid leaf desiccation directly inhibited gross photosynthesis.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Treatment
- Rapid leaf desiccatione0
- Outcome
- gross photosynthesise0
- Direction
- inhibitione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rapid leaf desiccation caused changes in the low frequency photoacoustic signal, attributed both to the mechanism of signal transduction, influenced by changes in the structural parameters of the leaf, and to the direct (nonstomatal) inhibition of gross photosynthesis”
e1“tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
A low frequency photothermal component increased with desiccation.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Treatment
- desiccation treatmente0
- Outcome
- photothermal componentse2
- Direction
- increasede0
- Qualifier
- below about 100 Hze0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“one of which persisted only at low modulation frequencies (below about 100 Hz) and which largely increased with the desiccation treatment”
e1“tobacco (Nicotiana tabacum L.)”
e2“two photothermal components”
Claim · model-written summary
The other photothermal component was nonvariable.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Outcome
- nonvariable photothermal componente0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The other nonvariable photothermal component was ascribed to a thermal wave propagating from the chloroplasts to the surface of the mesophyll cell”
e1“tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Frequency dependence of the oxygen to photothermal signal ratio provided a comparative quantum yield parameter.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Outcome
- comparative quantum yield parametere0
- Comparator
- zero frequencye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The specific dependence of the latter ratio on the frequency yielded a comparative quantum yield parameter from its extrapolation to zero frequency”
e1“tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Water stress altered oxygen diffusion through mesophyll cells as reflected in the slope of the signal ratio.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Treatment
- stresse0
- Outcome
- diffusion of O(2) through the mesophyll celle0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stress induced changes in the diffusion of O(2) through the mesophyll cell, reflected by changes in its characteristic slope”
e1“tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Quantum yield declined markedly as water stress progressed.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Treatment
- water stresse0
- Outcome
- quantum yielde0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“quantum yield was markedly reduced with the progression of the water stress”
e1“tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Photoacoustic measurements at high modulation frequency showed stronger inhibition of photochemical energy storage.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Outcome
- photochemical energy storagee0
- Direction
- inhibitione0
- Setting
- high modulation frequencye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stronger inhibition of the photochemical energy storage, obtained by photoacoustic measurements at a high modulation frequency”
e1“tobacco (Nicotiana tabacum L.)”
The same questions in other papers
drought · physiology: photosynthesis · Nicotiana tabacum (tobacco)Positive and negative results
24 papers in the same direction as this paper · 1 in the opposite direction
- positive
- negative
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22 papers more in this group
See all 26 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.