Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (835 words), 9 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
A form of chlorophyll that absorbs light in the violet to red spectrum (approximately 400-700 nm wavelength range) and reflects green light (500-570 nm wavelength), which imparts the characteristic green color to land plants. It is essential for oxygenic photosynthesis.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Chlorophyll A2.
Where it fits in the MeSH classification
- Broader topics
- Chlorophyll
Related concepts
- Photosynthesis
Research landscape
PubMed indexes 6,510 records tagged with the MeSH heading “Chlorophyll A” (counts retrieved 2026-10-31). 2,581 of them (39.6%) were published from 2020 onward, and the busiest period so far is 2010-2019 with 2,581 records.
Reviews account for 86 records (1.3%) and meta-analyses for 16. Randomized controlled trials number 2 (0.0%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.
Show the data
| Period | Records |
|---|---|
| through 1999 | 200 |
| 2000-2009 | 1,148 |
| 2010-2019 | 2,581 |
| 2020 onward | 2,581 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 86 | 1.3% |
| Meta-analyses | 16 | 0.2% |
| Randomized controlled trials | 2 | 0.0% |
Method: PubMed query "Chlorophyll A"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in drugs and chemicals
Studies of a chemical or drug can answer very different questions: what it is and how it behaves in cells and animals, how the body handles it, and whether it changes outcomes in people. Laboratory and animal findings often do not carry over to patients, and observational studies of exposures are confounded by who uses a substance and why. Nothing on this page is a recommendation to use, avoid, start or stop any substance or medicine; talk to a qualified clinician or pharmacist about your own situation. Check the dose, the species, the comparison group and whether a patient-relevant outcome was measured.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
Nitrogen Starvation Impacts the Photosynthetic Performance of Porphyridium cruentum as Revealed by Chlorophyll a Fluorescence [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Nitrogen is one of the most important nutrients needed for plants and algae to survive, and the photosynthetic ability of algae is related to nitrogen abundance.
- Closing excerpt
- cruentum was severely impacted by nitrogen deficiency.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (191 words)
Nitrogen is one of the most important nutrients needed for plants and algae to survive, and the photosynthetic ability of algae is related to nitrogen abundance. Red algae are unique photosynthetic eukaryotic organisms in the evolution of algae, as they contain phycobilisomes (PBSs) on their thylakoid membranes. In this report, the in vivo chlorophyll (Chl) a fluorescence kinetics of nitrogen-starved Porphyridium cruentum were analyzed to determine the effects of nitrogen deficiency on photosynthetic performance using a multi-color pulse amplitude modulation (PAM) chlorophyll fluorometer. Due to nitrogen starvation, the photochemical efficiency of PSII and the activity of PSII reaction centers (RCs) decreased, and photoinhibition of PSII occurred. The water-splitting system on the donor side of PSII was seriously impacted by nitrogen deficiency, leading to the inactivation of the oxygen-evolving complex (OEC) and decreased light energy conversion efficiency. In nitrogen-starved cells, a higher proportion of energy was used for photochemical reactions, and thermal dissipation was reduced, as shown by qP and qN. The ability of nitrogen-starved cells to tolerate and resist high photon flux densities was weakened. Our results showed that the photosynthetic performance of P. cruentum was severely impacted by nitrogen deficiency.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 28819147 · DOI · PMC5561210
Metabolome and transcriptome analyses reveal chlorophyll and anthocyanin metabolism pathway associated with cucumber fruit skin color [2]
Abstract reading summary — source excerpts
- Opening excerpt
- BackgroundFruit skin color play important role in commercial value of cucumber, which is mainly determined by the content and composition of chlorophyll and anthocyanins.
- Closing excerpt
- We lay a foundation to understand molecular regulation mechanism on formation of cucumber skin color, by exploring valuable genes, which is helpful for cucumber breeding and improvement on fruit skin color.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (246 words)
BackgroundFruit skin color play important role in commercial value of cucumber, which is mainly determined by the content and composition of chlorophyll and anthocyanins. Therefore, understanding the related genes and metabolomics involved in composition of fruit skin color is essential for cucumber quality and commodity value.ResultsThe results showed that chlorophyll a, chlorophyll b and carotenoid content in fruit skin were higher in Lv (dark green skin) than Bai (light green skin) on fruit skin. Cytological observation showed more chloroplast existed in fruit skin cells of Lv. A total of 162 significantly different metabolites were found between the fruit skin of the two genotypes by metabolome analysis, including 40 flavones, 9 flavanones, 8 flavonols, 6 anthocyanins, and other compounds. Crucial anthocyanins and flavonols for fruit skin color, were detected significantly decreased in fruit skin of Bai compared with Lv. By RNA-seq assay, 4516 differentially expressed genes (DEGs) were identified between two cultivars. Further analyses suggested that low expression level of chlorophyll biosynthetic genes, such as chlM, por and NOL caused less chlorophylls or chloroplast in fruit skin of Bai. Meanwhile, a predicted regulatory network of anthocyanin biosynthesis was established to illustrate involving many DEGs, especially 4CL, CHS and UFGT.ConclusionsThis study uncovered significant differences between two cucumber genotypes with different fruit color using metabolome and RNA-seq analysis. We lay a foundation to understand molecular regulation mechanism on formation of cucumber skin color, by exploring valuable genes, which is helpful for cucumber breeding and improvement on fruit skin color.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 32831013 · DOI · PMC7444041
Rate-limiting steps in the dark-to-light transition of Photosystem II - revealed by chlorophyll-a fluorescence induction [3]
Abstract reading summary — source excerpts
- Opening excerpt
- Photosystem II (PSII) catalyses the photoinduced oxygen evolution and, by producing reducing equivalents drives, in concert with PSI, the conversion of carbon dioxide to sugars.
- Closing excerpt
- In experiments using double flashes with variable waiting times (∆τ) between them, we found that no rise could be induced with zero or short ∆τ, the value of which depended on the temperature - revealing a previously unknown rate-limiting step in PSII.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (200 words)
Photosystem II (PSII) catalyses the photoinduced oxygen evolution and, by producing reducing equivalents drives, in concert with PSI, the conversion of carbon dioxide to sugars. Our knowledge about the architecture of the reaction centre (RC) complex and the mechanisms of charge separation and stabilisation is well advanced. However, our understanding of the processes associated with the functioning of RC is incomplete: the photochemical activity of PSII is routinely monitored by chlorophyll-a fluorescence induction but the presently available data are not free of controversy. In this work, we examined the nature of gradual fluorescence rise of PSII elicited by trains of single-turnover saturating flashes (STSFs) in the presence of a PSII inhibitor, permitting only one stable charge separation. We show that a substantial part of the fluorescence rise originates from light-induced processes that occur after the stabilisation of charge separation, induced by the first STSF; the temperature-dependent relaxation characteristics suggest the involvement of conformational changes in the additional rise. In experiments using double flashes with variable waiting times (∆τ) between them, we found that no rise could be induced with zero or short ∆τ, the value of which depended on the temperature - revealing a previously unknown rate-limiting step in PSII.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 29426901 · DOI · PMC5807364
Portable Multispectral Fluorometer with Embedded Machine Learning for Chlorophyll-a Estimation in Acetone-Extracted Samples [4]
Abstract reading summary — source excerpts
- Opening excerpt
- Chlorophyll-a (Chl-a) is commonly used as an indicator of phytoplankton biomass and water quality, but its determination usually depends on laboratory-based methods and specialized equipment.
- Closing excerpt
- These results suggest that the system is a promising portable alternative for Chl-a estimation in prepared acetone extracts under the evaluated conditions.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (198 words)
Chlorophyll-a (Chl-a) is commonly used as an indicator of phytoplankton biomass and water quality, but its determination usually depends on laboratory-based methods and specialized equipment. In this work, a portable multispectral fluorometer was developed and evaluated for Chl-a estimation in 90% acetone extracts prepared from water samples. The system integrates a nominal 420-425 nm fluorescence excitation source, 90° detection geometry, two multispectral sensors (AS7341 and AS7343), an ESP32-S3 microcontroller, and an Android application for device control and result visualization. A dataset of 76 samples was used for model development, including regression-model benchmarking, model selection, and internal testing. A Random Forest model selected for embedded implementation was exported to C++ for on-device inference. Validation using 15 independent samples yielded R2 = 0.979, root mean square error (RMSE) = 35.41 µg/L, mean absolute error (MAE) = 28.91 µg/L, and mean absolute percentage error (MAPE) = 6.14%. Agreement analysis showed a positive bias of 22.00 µg/L, while repeatability tests showed a maximum coefficient of variation (CV) of 3.29%. Embedded inference was highly consistent with Python predictions (R2 = 0.997). These results suggest that the system is a promising portable alternative for Chl-a estimation in prepared acetone extracts under the evaluated conditions.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42451328 · DOI · PMC13364246
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Photosynthesis: basics, history and modelling [5]
- Research article Chlorophyll a fluorescence illuminates a path connecting plant molecular biology to Earth-system science [6]
- Research article Silver Island Film for Enhancing Light Harvesting in Natural Photosynthetic Proteins [7]
- Research article Recent advances in plant stress analysis using chlorophyll a fluorescence [8]
- Research article Current and emerging techniques for oceanic and lake chlorophyll-a estimation and monitoring: a global perspective [9]
References
- Zhao LS, Li K, Wang QM, Song XY, Su HN, Xie BB, et al.. Nitrogen Starvation Impacts the Photosynthetic Performance of Porphyridium cruentum as Revealed by Chlorophyll a Fluorescence. . 2017. PMID 28819147 · DOI · PMC5561210
- Wang M, Chen L, Liang Z, He X, Liu W, Jiang B, et al.. Metabolome and transcriptome analyses reveal chlorophyll and anthocyanin metabolism pathway associated with cucumber fruit skin color. . 2020. PMID 32831013 · DOI · PMC7444041
- Magyar M, Sipka G, Kovács L, Ughy B, Zhu Q, Han G, et al.. Rate-limiting steps in the dark-to-light transition of Photosystem II - revealed by chlorophyll-a fluorescence induction. . 2018. PMID 29426901 · DOI · PMC5807364
- Blanco-Jáquez AD, Alarcón-Herrera MT, Valenzuela-García LI, Marín-Celestino AE, Villarreal-Rodríguez S, Ayala-García VM, et al.. Portable Multispectral Fluorometer with Embedded Machine Learning for Chlorophyll-a Estimation in Acetone-Extracted Samples. . 2026. PMID 42451328 · DOI · PMC13364246
- Stirbet A, Stirbet A, Lazár D, Guo Y, Govindjee G. Photosynthesis: basics, history and modelling. Ann Bot. 2020. PMID 31641747 · DOI · PMC7489092
- Porcar-Castell A, Malenovský Z, Magney T, Van Wittenberghe S, Fernández-Marín B, Maignan F, et al.. Chlorophyll a fluorescence illuminates a path connecting plant molecular biology to Earth-system science. Nat Plants. 2021. PMID 34373605 · DOI
- Kowalska D, Szalkowski M, Sulowska K, Buczynska D, Niedziolka-Jonsson J, Jonsson-Niedziolka M, et al.. Silver Island Film for Enhancing Light Harvesting in Natural Photosynthetic Proteins. Int J Mol Sci. 2020. PMID 32244795 · DOI · PMC7177865
- Chang KW, Tang H, Fu LJ, Xia Q, Pan ZY, Tan JL, et al.. Recent advances in plant stress analysis using chlorophyll a fluorescence. Photosynthetica. 2025. PMID 41551680 · DOI · PMC12805462
- Jena R, Shanableh A, Al-Ruzouq R, Gibril MBA, Hammouri NA, Farweh FH, et al.. Current and emerging techniques for oceanic and lake chlorophyll-a estimation and monitoring: a global perspective. Environ Monit Assess. 2026. PMID 41787006 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.