the energy to drive photosynthesis comes from chemical energy.
where does the energy to drive photosynthesis come from?
chemical energy
in general, photoacoustic measurements of energy storage require a reference sample for comparison. it is a sample with exactly the same light absorption (at the given excitation wavelength) but which completely degrades all the absorbed light into heat within the time resolution of the measurement. it is lucky that photosynthetic systems are self-calibrating, providing such a reference in one sample, as follows: one compares two signals: one, which is obtained with the probing modulated/pulsed light alone and the other when a steady non-modulated light (referred to as "background light"), which is strong enough to drive photosynthesis into saturation, is added. the added steady light does not produce any photoacoustic effect by itself, but changes the photoacoustic response due to the modulated/pulsed probing light. the resulting signal serves as a reference to all other measurements in absence of the background light. the photothermal part of the reference signal is maximal, since at photosynthetic saturation no energy is stored. at the same time the contribution of the other mechanisms tends to zero at saturation. thus the reference signal is proportional to the total absorbed light energy.
photoacoustic effect
other photosynthetic bacterioplankton, including purple and green bacteria, undergo anoxygenic photosynthesis in anaerobic conditions. the pigments synthesized in these organisms are sensitive to oxygen. in purple bacteria the major pigments include bacteriochlorophyll a and b and carotenoids. green bacteria have different light harvesting pigments consisting of bacteriochlorophyll c, d and e. these organisms do not produce oxygen through photosynthesis or use water as a reducing agent. many of these organisms use sulfur, hydrogen or other compounds as an energy source to drive photosynthesis. most of these bacterioplankton are found in anoxic waters, including stagnant and hypersaline environments.





























section::::major groups.:heterotrophic bacterioplankton.
bacterioplankton