Abstract
Abstract Studies have shown that the rapid turnover of the photosystem II reaction centre D1 protein is linked to the photosynthetic rate in higher plant leaves. Initially this research involved analysing the techniques that are used to assess photosynthetic activity. Leaf photosynthetic and electron transport rates and photosystem II protein turnover were measured in a series of experiments. From the rates determined, the underlying mechanisms that determine the actual rate of photosynthesis and the maximum photosynthetic capacity in leaves of higher plants were explored. In Phaseolus vulgaris, maximum photosynthetic capacity determined from CO2 fixation rates was compared with maximum electron transport rates measured via chlorophyll fluorescence. These experiments showed that the PSII electron transport rates did not reflect the maximum electron transport capacity unless light and other conditions were optimal. From the maximum ETRs and the maximum CO2 fixation rates a relationship between the two rates was derived. It was also concluded that combined gas exchange analysis and chlorophyll fluorescence derived ETRs may allow determination of non-linear electron flow. In Triticum aestivum plants under water, temperature and nitrogen stress D1 turnover and photosynthetic rates were measured. The results of these experiments suggest that D1 metabolism plays a significant role in the stress response in higher plants and that it does not limit/inhibit or restrict O2 evolution, PSII electron transport activity or PSII efficiency. D1 synthesis rates were examined in vivo from leaves that had been exposed to different concentrations of the glutamine synthetase inhibitor methionine sulfoximine. In these experiments D1 synthesis was significantly linearly related with maximum ETRs as well as O2 evolution rates and PSII efficiency. It was evident that high light and photoinhibition are not the sole triggers for changes in D1 synthesis rate. D1 turnover may be a constitutive activity, its rate related to the functional state of PSII, i.e. whether it is electron transport active or dissipative. A regulation link between D1 synthesis and photosynthetic activity is suggested. Different forms of the D1 protein generated under varying light regimes were examined in Pisum sativum. It was found that the D1 protein undergoes conformational changes or post-translational modifications in response to irradiance. Different D1 specific antibodies did not detect all the forms of D1, thus showing that Western blotting is not always a reliable technique for measuring net D1 content. Preliminary evidence suggested that the different forms of D1 may have different functional roles and may be associated with functionally distinct PSIIs. A model relating D1 structural differences and D1 metabolism is proposed. Finally, it is suggested that D1 protein metabolism, synthesis in particular, is linked to PSII electron transport activity and to feedback from various metabolic pathways. This research provides further evidence that D1 turnover plays a key role in photosynthetic regulation.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher.
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 12
Claim · model-written summary
PSII electron transport rates did not reflect maximum capacity unless light and other conditions were optimal in Phaseolus vulgaris.
- Taxon
- Phaseolus vulgaris
Phaseolus vulgarise0 - Outcome
- PSII electron transport ratese0
- Qualifier
- unless light and other conditions were optimale0
- Comparator
- maximum electron transport capacitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In Phaseolus vulgaris, maximum photosynthetic capacity determined from CO2 fixation rates was compared with maximum electron transport rates measured via chlorophyll fluorescence. These experiments showed that the PSII electron transport rates did not reflect the maximum electron transport capacity unless light and other conditions were optimal.”
Claim · model-written summary
Maximum ETR and CO2 fixation rates yielded a relationship between the two rates.
- Taxon
- higher plantsEmbryophytat0
- Outcome
- a relationship between the two ratese0
- Comparator
- maximum CO2 fixation ratese0
Not reportedDirection
Verbatim
e0“From the maximum ETRs and the maximum CO2 fixation rates a relationship between the two rates was derived.”
t0“leaves of higher plants”
Claim · model-written summary
Combined gas exchange and chlorophyll fluorescence ETR may enable determination of nonlinear electron flow.
- Taxon
- higher plantsEmbryophytat0
- Outcome
- determination of non-linear electron flowe0
- Comparator
- combined gas exchange analysis and chlorophyll fluorescence derived ETRse0
Verbatim
e0“combined gas exchange analysis and chlorophyll fluorescence derived ETRs may allow determination of non-linear electron flow.”
t0“leaves of higher plants”
Claim · model-written summary
D1 metabolism was implicated in the stress response of Triticum aestivum.
- Taxon
- Triticum aestivum
Triticum aestivume0 - Treatment
- water, temperature and nitrogen stresse0
- Gene
- D1e0
- Outcome
- stress responsee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In Triticum aestivum plants under water, temperature and nitrogen stress D1 turnover and photosynthetic rates were measured. The results of these experiments suggest that D1 metabolism plays a significant role in the stress response in higher plants”
Claim · model-written summary
D1 metabolism did not limit O2 evolution, PSII electron transport activity, or PSII efficiency under stress.
- Taxon
- Triticum aestivumTriticum aestivumt0
- Gene
- D1e0
- Outcome
- O2 evolution, PSII electron transport activity or PSII efficiencye0
- Direction
- does not limit/inhibit or restricte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“D1 metabolism plays a significant role in the stress response in higher plants and that it does not limit/inhibit or restrict O2 evolution, PSII electron transport activity or PSII efficiency.”
t0“In Triticum aestivum plants under water”
Claim · model-written summary
D1 synthesis was significantly linearly related to maximum ETR, O2 evolution, and PSII efficiency.
- Taxon
- Triticum aestivumTriticum aestivumt0
- Treatment
- methionine sulfoximinee0
- Gene
- D1e0
- Outcome
- maximum ETRs as well as O2 evolution rates and PSII efficiencye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“D1 synthesis rates were examined in vivo from leaves that had been exposed to different concentrations of the glutamine synthetase inhibitor methionine sulfoximine. In these experiments D1 synthesis was significantly linearly related with maximum ETRs as well as O2 evolution rates and PSII efficiency.”
t0“In Triticum aestivum plants under water”
Claim · model-written summary
High light and photoinhibition were not the sole triggers of D1 synthesis changes.
- Taxon
- Triticum aestivumTriticum aestivumt0
- Gene
- D1e0
- Outcome
- changes in D1 synthesis ratee0
- Qualifier
- high light and photoinhibitione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high light and photoinhibition are not the sole triggers for changes in D1 synthesis rate.”
t0“In Triticum aestivum plants under water”
Claim · model-written summary
D1 turnover may be constitutive and related to PSII functional state.
- Taxon
- Triticum aestivumTriticum aestivumt0
- Gene
- D1e0
- Outcome
- D1 turnovere0
- Qualifier
- functional state of PSIIe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“D1 turnover may be a constitutive activity, its rate related to the functional state of PSII, i.e. whether it is electron transport active or dissipative.”
t0“In Triticum aestivum plants under water”
Claim · model-written summary
D1 protein forms changed conformation or modification in response to irradiance in Pisum sativum.
- Taxon
- Pisum sativum
Lathyrus oleraceuse0 - Treatment
- varying light regimese0
- Gene
- D1 proteine0
- Outcome
- conformational changes or post-translational modificationse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Different forms of the D1 protein generated under varying light regimes were examined in Pisum sativum. It was found that the D1 protein undergoes conformational changes or post-translational modifications in response to irradiance.”
Claim · model-written summary
D1 antibodies did not detect all D1 forms, limiting Western blot measurement of net content.
- Taxon
- Pisum sativumLathyrus oleraceust0
- Gene
- D1e0
- Outcome
- measuring net D1 contente0
- Comparator
- Different D1 specific antibodiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Different D1 specific antibodies did not detect all the forms of D1, thus showing that Western blotting is not always a reliable technique for measuring net D1 content.”
t0“in Pisum sativum”
Claim · model-written summary
Different D1 forms may have distinct functions associated with distinct PSIIs.
- Taxon
- Pisum sativumLathyrus oleraceust0
- Gene
- D1e0
- Outcome
- different functional rolese0
- Qualifier
- functionally distinct PSIIse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Preliminary evidence suggested that the different forms of D1 may have different functional roles and may be associated with functionally distinct PSIIs.”
t0“in Pisum sativum”
Claim · model-written summary
The authors propose that D1 synthesis links to PSII electron transport and metabolic feedback.
- Taxon
- Pisum sativumLathyrus oleraceust0
- Gene
- D1 proteine0
- Outcome
- PSII electron transport activitye0
- Qualifier
- feedback from various metabolic pathwayse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“D1 protein metabolism, synthesis in particular, is linked to PSII electron transport activity and to feedback from various metabolic pathways.”
t0“in Pisum sativum”