Abstract
The effect of rapid dehydration of detached tobacco leaves (Nicotiana tabacum L.) on the photochemical apparatus of photosynthesis was studied in vivo by a combination of methods: photoacoustics, chlorophyll a fluorescence, and cytochrome f difference spectroscopy. It was shown that the inhibition of gross O(2) evolution was mainly caused by inactivation of PSII: (a) The saturation curve of cytochrome-f photooxidation by farred (>710 nanometers) light was resistant to the stress, leading to the conclusion that photosystem I (PSI) was largely unaffected by the stress. (b) The extent of the chlorophyll a variable fluorescence arising from photosystem II (PSII) decreased with the progression of the stress, but was largely unaffected when the leaf was preincubated with electron donors to PSII, such as hydroxylamine. It is concluded that the drought damage to PSII occurred on the photooxidative side. Despite the extensive inhibition of PSII and the relative preservation of PSI, the apparent PSII/PSI activity balance was somewhat larger in stressed leaves than in the control, as indicated by photoacoustic measurements of Emerson enhancement. These measurements were performed continuously under conditions which favor transitions to either state 1 or 2, showing that the transition to state 2 was considerably inhibited. Simultaneous measurements of chlorophyll fluorescence induction at 680 and 730 mm at room temperature were also used to probe changes in energy distribution between PSII and PSI and indicated that the transition from a dark adapted state to state 2 was also affected in water-stressed leaves. The saturation curve of the far-red light effect in Emerson enhancement was not changed by the stress, giving another independent evidence for the drought resistance of PSI activity. This apparent preservation of the imbalance in photochemical activities in favor of PSII, despite the fact that PSII is strongly inhibited, and PSI is not, supports a previous suggestion that the electron transfer between the two photosystems is not random but that a large extent of PSII and PSI units are specifically linked.
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Claims 10
Claim · model-written summary
Rapid dehydration inhibited gross oxygen evolution mainly through PSII inactivation.
- Taxon
- tobacco
Nicotiana tabacume1 - Treatment
- rapid dehydratione2
- Outcome
- gross O(2) evolutione0
- Qualifier
- inactivation of PSIIe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the inhibition of gross O(2) evolution was mainly caused by inactivation of PSII”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
e2“rapid dehydration”
Claim · model-written summary
The far-red cytochrome-f photooxidation saturation curve resisted dehydration, indicating PSI was largely unaffected.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- rapid dehydratione2
- Outcome
- saturation curve of cytochrome-f photooxidatione0
- Direction
- resistante0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The saturation curve of cytochrome-f photooxidation by farred (>710 nanometers) light was resistant to the stress”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
e2“rapid dehydration”
Claim · model-written summary
PSII variable chlorophyll fluorescence declined as dehydration progressed.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- progression of the stresse0
- Outcome
- chlorophyll a variable fluorescencee0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The extent of the chlorophyll a variable fluorescence arising from photosystem II (PSII) decreased with the progression of the stress”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
Claim · model-written summary
PSII electron donors largely prevented the stress associated decrease in variable fluorescence.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- preincubated with electron donors to PSII, such as hydroxylaminee0
- Outcome
- chlorophyll a variable fluorescencee2
- Direction
- largely unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“was largely unaffected when the leaf was preincubated with electron donors to PSII, such as hydroxylamine”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
e2“chlorophyll a variable fluorescence arising from photosystem II (PSII)”
Claim · model-written summary
Drought damage to PSII occurred on its photooxidative side.
- Taxon
- tobaccoNicotiana tabacume1
- Outcome
- drought damage to PSIIe0
- Qualifier
- photooxidative sidee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“drought damage to PSII occurred on the photooxidative side”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
Claim · model-written summary
Apparent PSII/PSI activity balance was somewhat larger in stressed leaves than controls.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- stressed leavese0
- Outcome
- apparent PSII/PSI activity balancee0
- Direction
- largere0
- Comparator
- controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the apparent PSII/PSI activity balance was somewhat larger in stressed leaves than in the control”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
Claim · model-written summary
Transition to state 2 was considerably inhibited in stressed tobacco leaves.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- stressed leavese2
- Outcome
- transition to state 2e0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the transition to state 2 was considerably inhibited”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
e2“somewhat larger in stressed leaves”
Claim · model-written summary
Transition from dark adaptation to state 2 was affected by water stress.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- water-stressed leavese0
- Outcome
- transition from a dark adapted state to state 2e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the transition from a dark adapted state to state 2 was also affected in water-stressed leaves”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
Claim · model-written summary
Far-red light saturation effect in Emerson enhancement was unchanged by stress.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- stresse0
- Outcome
- saturation curve of the far-red light effect in Emerson enhancemente0
- Direction
- not changede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The saturation curve of the far-red light effect in Emerson enhancement was not changed by the stress”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
Claim · model-written summary
The photochemical activity imbalance supports specific links between PSII and PSI units.
- Taxon
- tobaccoNicotiana tabacume1
- Outcome
- electron transfer between the two photosystemse2
- Qualifier
- PSII and PSI units are specifically linkede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a large extent of PSII and PSI units are specifically linked”
e1“detached tobacco leaves (Nicotiana tabacum L.)”
e2“the electron transfer between the two photosystems is not random”
The same questions in other papers
drought · molecular: metabolites · Nicotiana tabacum (tobacco)Positive and negative results
7 papers in the same direction as this paper · 6 in the opposite direction
- positive
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See all 14 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.