Explanation
When the plant is illuminated the fluorescence intensity increases with a time constant in the microsecond or millisecond range. After a few seconds the intensity falls again and finally reaches a steady-state level. The initial rise of the fluorescence intensity (A) is attributed to the progressive saturation of the reaction centers in the photosynthesis. Therefore the quenching of the fluorescence by the photosynthesis decreases with the time of illumination, with a corresponding increase of the fluorescence intensity. The quenching by the photosynthesis pathway is called photochemical quenching. The slow decrease of the fluorescence intensity at later times (B) is termed non-photochemical quenching. Non-photochemical quenching is most likely due to a protection mechanism the plant has to avoid the adverse effect of an excess of light. Several processes cause non-photochemical quenching, e.g. photoinhibition.
Read more about this topic: Kautsky Effect
Famous quotes containing the word explanation:
“Young children constantly invent new explanations to account for complex processes. And since their inventions change from week to week, furnishing the “correct” explanation is not quite so important as conveying a willingness to discuss the subject. Become an “askable parent.””
—Ruth Formanek (20th century)
“My companion assumes to know my mood and habit of thought, and we go on from explanation to explanation, until all is said that words can, and we leave matters just as they were at first, because of that vicious assumption.”
—Ralph Waldo Emerson (1803–1882)
“Natural selection, the blind, unconscious, automatic process which Darwin discovered, and which we now know is the explanation for the existence and apparently purposeful form of all life, has no purpose in mind. It has no mind and no mind’s eye. It does not plan for the future. It has no vision, no foresight, no sight at all. If it can be said to play the role of the watchmaker in nature, it is the blind watchmaker.”
—Richard Dawkins (b. 1941)