The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
Find out more about space activities in our 23 Member States, and understand how ESA works together with their national agencies, institutions and organisations.
Exploring our Solar System and unlocking the secrets of the Universe
Go to topicProtecting life and infrastructure on Earth and in orbit
Go to topicUsing space to benefit citizens and meet future challenges on Earth
Go to topicMaking space accessible and developing the technologies for the future
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When plants convert atmospheric carbon dioxide and sunlight into energy-rich carbohydrates through the process of photosynthesis, not all of the energy produced during this ‘light reaction’ can be consumed. Plants have evolved a mechanism to rid themselves of this extra energy by emitting fluorescence, which is light at a longer wavelength than that absorbed. In optimal conditions, plants use about 82% of the light they absorb for growth, with the remainder lost as heat and emitted as fluorescence.
The emission of chlorophyll fluorescence emanates from two photosystems involved in the light reaction: PS II and PS I. Chlorophyll fluorescence produced from the initial reactions in PS II occurs at wavelengths between 650–780 nm with a peak at around 685 nm. In the case of PS I, fluorescence occurs almost exclusively in the far-red/near-infrared spectrum (>700 nm, with a peak at about 740 nm). The full chlorophyll emission spectrum covers a wavelength range in the visible to near-infrared spectrum of 640–800 nm. Both photosystems operate in a reaction chain and are commonly measured as a two-peak signal.