Abstract
The chlorophyll fluorescence induction curves from mesophyll and guard cell chloroplasts of Saxifraga cernua, including both the fast (O to P, the transients involved in the rise in variable fluorescence) and slow (P to steady state fluorescence due to quenching) components, were characterized over a range of excitation intensities using microspectrophotometry (with epi-lumination) equipped with apertures designed to eliminate cross contamination of the fluorescence signal between the two chloroplast types. At low excitation intensities, the fast fluorescence kinetics from guard cell plastids showed an extended I to D phase and a more rapid appearance of P while minimal quenching from P to steady state fluorescence was observed compared to the transients from mesophyll chloroplasts suggesting a lower activity of photochemical (electron movement via carriers between donor and acceptor sites) and nonphotochemical (such as membrane conformational changes) events which regulate the fluorescence induction curve kinetics. As the excitation intensity was increased, the quenching rates of guard cells were faster at initiating conditions for photophosphorylation and the fast and slow fluorescence kinetics from guard cells resembled those of the mesophyll cells.Guard cell chloroplasts of S. cernua from intact epidermal peels showed a low temperature (77 K) fluorescence emission spectrum having three major peaks (at 685, 695, and 730 nanometers when excited at 440 nanometers) which were qualitatively similar to those in the spectrum obtained from mesophyll tissue.These data suggest that S. cernua guard cell chloroplast photosystems I and II contribute to light-dependent stomatal activity only at high light intensities.
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Claims 8
Claim · model-written summary
At low excitation intensities, guard cell chloroplasts showed an extended I to D phase in fast fluorescence induction compared with mesophyll chloroplasts.
- Taxon
- Saxifraga cernua
Saxifraga cernuae0 - Organ / stage
- guard cell plastidse1
- Outcome
- I to D phasee1
- Direction
- extendede1
- Qualifier
- At low excitation intensitiese1
- Comparator
- mesophyll chloroplastse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll fluorescence induction curves from mesophyll and guard cell chloroplasts of Saxifraga cernua”
e1“At low excitation intensities, the fast fluorescence kinetics from guard cell plastids showed an extended I to D phase and a more rapid appearance of P while minimal quenching from P to steady state fluorescence was observed compared to the transients from mesophyll chloroplasts”
Claim · model-written summary
At low excitation intensities, guard cell chloroplasts showed a more rapid appearance of P compared with mesophyll chloroplasts.
- Taxon
- Saxifraga cernuaSaxifraga cernuae0
- Organ / stage
- guard cell plastidse1
- Outcome
- appearance of Pe1
- Direction
- more rapide1
- Qualifier
- At low excitation intensitiese1
- Comparator
- mesophyll chloroplastse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll fluorescence induction curves from mesophyll and guard cell chloroplasts of Saxifraga cernua”
e1“At low excitation intensities, the fast fluorescence kinetics from guard cell plastids showed an extended I to D phase and a more rapid appearance of P while minimal quenching from P to steady state fluorescence was observed compared to the transients from mesophyll chloroplasts”
Claim · model-written summary
At low excitation intensities, guard cell chloroplasts showed minimal quenching from P to steady state fluorescence compared with mesophyll chloroplasts.
- Taxon
- Saxifraga cernuaSaxifraga cernuae0
- Organ / stage
- guard cell plastidse1
- Outcome
- quenching from P to steady state fluorescencee1
- Direction
- minimale1
- Qualifier
- At low excitation intensitiese1
- Comparator
- mesophyll chloroplastse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll fluorescence induction curves from mesophyll and guard cell chloroplasts of Saxifraga cernua”
e1“At low excitation intensities, the fast fluorescence kinetics from guard cell plastids showed an extended I to D phase and a more rapid appearance of P while minimal quenching from P to steady state fluorescence was observed compared to the transients from mesophyll chloroplasts”
Claim · model-written summary
As excitation intensity increased, quenching rates of guard cells were faster at initiating conditions for photophosphorylation.
- Taxon
- Saxifraga cernuaSaxifraga cernuae0
- Organ / stage
- guard cellse2
- Treatment
- excitation intensity was increasede2
- Outcome
- quenching ratese2
- Direction
- fastere2
- Qualifier
- at initiating conditions for photophosphorylatione2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll fluorescence induction curves from mesophyll and guard cell chloroplasts of Saxifraga cernua”
e2“As the excitation intensity was increased, the quenching rates of guard cells were faster at initiating conditions for photophosphorylation”
Claim · model-written summary
At increased excitation intensity, fast and slow fluorescence kinetics of guard cells resembled those of mesophyll cells.
- Taxon
- Saxifraga cernuaSaxifraga cernuae0
- Organ / stage
- guard cellse3
- Outcome
- fast and slow fluorescence kineticse3
- Direction
- resemblede3
- Comparator
- mesophyll cellse3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll fluorescence induction curves from mesophyll and guard cell chloroplasts of Saxifraga cernua”
e3“the fast and slow fluorescence kinetics from guard cells resembled those of the mesophyll cells”
Claim · model-written summary
Guard cell chloroplasts of S. cernua showed a 77 K fluorescence emission spectrum with three major peaks at 685, 695 and 730 nm when excited at 440 nm.
- Taxon
- S. cernuaSaxifraga cernuae4
- Organ / stage
- Guard cell chloroplastse4
- Outcome
- low temperature (77 K) fluorescence emission spectrume4
- Value
- 685, 695, and 730 nanometerse4
- Qualifier
- when excited at 440 nanometerse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“Guard cell chloroplasts of S. cernua from intact epidermal peels showed a low temperature (77 K) fluorescence emission spectrum having three major peaks (at 685, 695, and 730 nanometers when excited at 440 nanometers)”
Claim · model-written summary
The 77 K emission spectrum of guard cell chloroplasts was qualitatively similar to that of mesophyll tissue.
- Taxon
- S. cernuaSaxifraga cernuae4
- Organ / stage
- Guard cell chloroplastse4
- Outcome
- fluorescence emission spectrume4
- Direction
- qualitatively similare5
- Comparator
- mesophyll tissuee5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“Guard cell chloroplasts of S. cernua from intact epidermal peels showed a low temperature (77 K) fluorescence emission spectrum having three major peaks (at 685, 695, and 730 nanometers when excited at 440 nanometers)”
e5“which were qualitatively similar to those in the spectrum obtained from mesophyll tissue”
Claim · model-written summary
Photosystems I and II of guard cell chloroplasts contribute to light-dependent stomatal activity only at high light intensities.
- Taxon
- S. cernuaSaxifraga cernuae6
- Organ / stage
- guard cell chloroplast photosystems I and IIe6
- Outcome
- light-dependent stomatal activitye6
- Qualifier
- only at high light intensitiese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e6“S. cernua guard cell chloroplast photosystems I and II contribute to light-dependent stomatal activity only at high light intensities”