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The daily light integral (DLI) is the number of photosynthetically active photons (photons in the PAR range) accumulated in a square meter over the course of a day. It is a function of photosynthetic light intensity and duration (day length) and is usually expressed as moles of light (mol photons) per square meter (m −2) per day (d −1), or: mol·m −2 ·d −1.
Light-dependent reactions of photosynthesis at the thylakoid membrane. Light-dependent reactions are certain photochemical reactions involved in photosynthesis, the main process by which plants acquire energy. There are two light dependent reactions: the first occurs at photosystem II (PSII) and the second occurs at photosystem I (PSI).
Cyanobacteria is the only prokaryotic group that performs oxygenic photosynthesis. Anoxygenic photosynthetic bacteria use PSI- and PSII-like photosystems, which are pigment protein complexes for capturing light. [5] Both of these photosystems use bacteriochlorophyll. There are multiple hypotheses for how oxygenic photosynthesis evolved.
The following is a breakdown of the energetics of the photosynthesis process from Photosynthesis by Hall and Rao: [6]. Starting with the solar spectrum falling on a leaf, 47% lost due to photons outside the 400–700 nm active range (chlorophyll uses photons between 400 and 700 nm, extracting the energy of one 700 nm photon from each one)
At the reaction center, there are many polypeptides that are surrounded by pigment proteins. At the center of the reaction center is a special pair of chlorophyll molecules. Each PSII has about 8 LHCII. These contain about 14 chlorophyll a and chlorophyll b molecules, as well as about four carotenoids. In the reaction center of PSII of plants ...
The antenna pigments are predominantly chlorophyll b, xanthophylls, and carotenes. Chlorophyll a is known as the core pigment. Their absorption spectra are non-overlapping and broaden the range of light that can be absorbed in photosynthesis. The carotenoids have another role as an antioxidant to prevent photo-oxidative damage of chlorophyll ...
Photoheterotrophs generate ATP using light, in one of two ways: [6] [7] they use a bacteriochlorophyll-based reaction center, or they use a bacteriorhodopsin.The chlorophyll-based mechanism is similar to that used in photosynthesis, where light excites the molecules in a reaction center and causes a flow of electrons through an electron transport chain (ETS).
The formula provided a reliable method of measuring chlorophyll content from 41 mg m −2 up to 675 mg m −2 with a correlation r 2 value of 0.95. [ 28 ] Also, the chlorophyll concentration can be estimated by measuring the light transmittance through the plant leaves [ 29 ] .