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Photosynthesis evaluation technology by photon detection

We are working on the development and application of technology to evaluate photosynthesis using optical devices. This technology is expected to be applied to ecosystem conservation, agricultural chemical development, water purification, tree planting, aquaculture, and atmospheric evaluation.
As a foundation for a sustainable society, photosynthesis supplies food and biomass to our lives and industries, and plays an important role in environmental purification and ecosystem conservation.

Photosynthesis evaluation technology by photon detection

What is plant photon (delayed fluorescence)?

Plant photon is very weak luminescence detected from "photosynthetic organisms" such as algae and plants. It can be detected by a photon detector such as a photomultiplier tube or MPPC, or a high-sensitivity camera with a multiplication function.
By measuring plant photons, you can directly see the movement of photosynthesis. In photosynthesis, chlorophyll uses light energy to decompose water and extract electrons. Electrons are stored in the carrier molecule, most of which is used as energy for photosynthesis. A small part of the stored electrons are converted back to “plant photons”. Plant photons slowly shine in the dark after the external light is extinguished and can be detected with a high sensitivity camera with a photomultiplier tube.

Photosynthesis evaluation technology by photon detection

■Related products

Photomultiplier tubes (PMTs)


Image intensifiers (IIs)

■Comparison of visible image and photon counting image

Visible image


Photon counting image



■Measurement of plant photons

Application : Rapid assessment of biological effects of water pollution with plant photons

It seems that 100,000 kinds of chemical substances are used all over the world. Hazard to humans and organisms (environmental risk) when released into the environment can be determined by chemical analysis and bioassay. Chemical analysis measures the amount of substances, and instruments such as GC / MS and LC / MS are used. Bioassay is a technique that uses living organisms to examine the relationship between the amount of substances and their toxicity. Fish, daphnia, algae, plants, etc. are used. The relationship between the two can be used to judge the hazard risk of chemical substances and to develop safe chemical substances.

Photosynthesis evaluation technology by photon detection

Plant photons are expected to be useful in bioassays to assess water pollution. Algae grow through biomass production by photosynthesis. If the algae metabolism is inhibited by chemical substances, biomass production will decrease and the growth rate will decrease. In conventional bioassays, growth inhibition is evaluated by counting the number of cells. We have developed a technique to estimate growth inhibition in a short time by evaluating the luminescence inhibition of plant photons that reflect photosynthesis. This technique is called algal luminescence toxicity test.

Photosynthesis evaluation technology by photon detection

Examples of organisms expected to utilize photosynthesis evaluation technology using photons

Aquaculture feeds, Chaetoceros

For the sustainable use of fishery resources, further development of aquaculture is expected. Algae has been cultivated in large quantities as aquaculture feeds.
Chaetoceros is one of the feed algae for shellfish and crustaceans.


Waterside ecosystem, Macrophytes

Macrophytes (aquatic plants) growing on the waterside and its surrounding ecosystems play a role as a place of water purification by absorption of nutrients and breeding of aquatic animals.
Duckweed is a familiar aquatic plant that grows in paddy fields.


Ocean biodiversity, Reef corals

Reef corals are animal, but It can do photosynthesis by symbiotic algae.
Although coral reefs are an important place for ocean biodiversity, it is said that 20% of coral reefs are destroyed and 50% are in danger. The cause is considered climate change and marine pollution.


Indicator of air pollution, Lichens

Lichens are composites of a fungus and an algae. It does photosynthesis with absorbing rain and minerals. Lichens population is decreased by air pollution, like a sulfur dioxide.
Parmotrema is a Lichen that proposed as indicator of air pollution in Japan.


Protein production, Spirulina

Proteins supplied from grain, animal husbandry and fishery products are concerned about supply shortage due to population increase and climate change. Algae is attracting attention as a new production source.
Spirulina is a protein-rich alga that can be provide in large scale, commercially.




  1. Masakazu Katsumata, Yuko Ikushima, Keith Bennett, Yukiko Sato, Ayano Takeuchi, Norihisa Tatarazako, Tomoyuki Hakamata,
    “Validation of rapid algal bioassay using delayed fluorescence in an interlaboratory ring study,”
    Science of The Total Environment, Volumes 605–606, 2017, Pages 842-851, ISSN 0048-9697,
  2. Ayano TAKEUCHI, Masakazu KATSUMATA, Takashi KOIKE, Yuri TAKATA, Yasuyuki ITATSU, Takashi KUSUI,
    “Comparison of the Conventional Algal Growth Inhibition Tests Using Cell Counting and Algal Bioassay Using Delayed Fluorescence: Application to Industrial Effluents, Journal of Water and Environment Technology,”
    2014, Volume 12, Issue 4, Pages 367-377, Released August 10, 2014, Online ISSN 1348-2165,
  3. Masakazu Katsumata, Ichiro Takeuchi,
    “Delayed fluorescence as an indicator of the influence of the herbicides Irgarol 1051 and Diuron on hard coral Acropora digitifera,”
    Marine Pollution Bulletin, Volume 124, Issue 2, 30 November 2017, Pages 687-693

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