Article Abstract:
Around half of plant production occurs in the oceans and the degree of imbalance between biological production and consumption is sustained, in principle, by imported or exported organic material. Deficits in organic matter need to be made up by inputs from terrestrial, freshwater and estuarine ecosystems. Calculations have shown that respiration exceeds photosynthesis in environments where net carbon fixation rates are low. An analysis of depth-integrated measures of production and respiration in five open-ocean regions was used to show that biological production generally exceeds consumption in the upper 100 m of the water column.
User Contributions:
Comment about this article or add new information about this topic:
Article Abstract:
Photosynthetic organisms can harvest sunlight efficiently, safely disposing of the dangerous excess excitation energy. Li and colleagues have used the fact that the rates of thermal energy dissipation can be examined non-intrusively in vivo from changes in chlorophyll fluorescence emission. They have shown that the presence of PsbS is needed for a change in the photosynthetic membrane engaging thermal energy dissipation. Such a change also requires zeaxanthin and a pH gradient over the photosynthetic membrane.
User Contributions:
Comment about this article or add new information about this topic:
Article Abstract:
Photosynthetic light harvesting in plants in controlled by changes in incident light intensity. MUtants of Arabidopsis thaliana that cannot dissipate excess absorbed light energy were isolated to identify certain proteins involved in nonphotochemical quenching. The gene encoding PsbS, a chlorophyll-binding protein of photosystem II, is required for nonphotochemical quenching, although not for efficient light harvesting and photosynthesis.
User Contributions:
Comment about this article or add new information about this topic: