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photosynthesis
ing colonies may form an economically important source of fertilizer.
~nutrients.
photic zonation three depth zones can be discerned in the water column according to light penetration. In the upper euphotic zone (also photic zone or photosynthetic zone) the rate of photosynthesis by algae is sufficient to compensate
for losses due to respiration (both during day and night). The lower boundary is approximately the depth where 1 % of the surface light is found. Below
this zone a dimly lighted disphotic zone is found where no effective photosynthesis occurs (algae cannot grow). In the deepest, lightless, aphotic zone no
photosynthesis is possible.
photoautotrophs ~metabolic diversity.
photochemical reactions the solar energy flux at the equator surface is equal to
about 6 10 21 photons cm- 2 day-l for visible and UV light. Part of it is absorbed
to initiate photochemical reactions through radical formations, resulting in
intramolecular rearrangement, isomerization, ionization, and intramolecular decomposition. The effect is greatest on surface films and in the euphotic zone.
photoheterotrophs ~metabolic diversity.
photoinhibition (syn. light inhibition) the depression in photosynthetic rate of
plants at high light intensities (above the light saturation point), resulting
from longer exposures and increasing with exposure time. Caused by
injury/destruction by UV of chlorophyll under high light intensities in the surface waters. ~Iight.
photolithotrophs ~metabolic diversity.
photoorganotrophs ~metabolic diversity.
photoperiod light period, in natural or artificial (experimental) light regime.
photosynthesis light-dependent assimilation of carbon dioxide into cellular organic compounds. In eukaryotic organisms photosynthesis occurs in cell organelles, i.e., chloroplasts (~chromatophore). In prokaryotes (phototrophic bacteria) photosystems are located on membranes in the cytoplasm. With H 2 0 as
electron donor oxygen is produced (oxygenic photosynthesis). Some photosynthetic bacteria can use hydrogen sulfide as an electron donor. The rate of photosynthesis is affected by many environmental factors such as the quality
and the intensity of light, temperature and the availability of nutrients.
Phytoplankton can adapt its photosynthetic activity to environmental conditions. This adaptation is species-dependent.
photosynthesis
ing colonies may form an economically important source of fertilizer.
~nutrients.
photic zonation three depth zones can be discerned in the water column according to light penetration. In the upper euphotic zone (also photic zone or photosynthetic zone) the rate of photosynthesis by algae is sufficient to compensate
for losses due to respiration (both during day and night). The lower boundary is approximately the depth where 1 % of the surface light is found. Below
this zone a dimly lighted disphotic zone is found where no effective photosynthesis occurs (algae cannot grow). In the deepest, lightless, aphotic zone no
photosynthesis is possible.
photoautotrophs ~metabolic diversity.
photochemical reactions the solar energy flux at the equator surface is equal to
about 6 10 21 photons cm- 2 day-l for visible and UV light. Part of it is absorbed
to initiate photochemical reactions through radical formations, resulting in
intramolecular rearrangement, isomerization, ionization, and intramolecular decomposition. The effect is greatest on surface films and in the euphotic zone.
photoheterotrophs ~metabolic diversity.
photoinhibition (syn. light inhibition) the depression in photosynthetic rate of
plants at high light intensities (above the light saturation point), resulting
from longer exposures and increasing with exposure time. Caused by
injury/destruction by UV of chlorophyll under high light intensities in the surface waters. ~Iight.
photolithotrophs ~metabolic diversity.
photoorganotrophs ~metabolic diversity.
photoperiod light period, in natural or artificial (experimental) light regime.
photosynthesis light-dependent assimilation of carbon dioxide into cellular organic compounds. In eukaryotic organisms photosynthesis occurs in cell organelles, i.e., chloroplasts (~chromatophore). In prokaryotes (phototrophic bacteria) photosystems are located on membranes in the cytoplasm. With H 2 0 as
electron donor oxygen is produced (oxygenic photosynthesis). Some photosynthetic bacteria can use hydrogen sulfide as an electron donor. The rate of photosynthesis is affected by many environmental factors such as the quality
and the intensity of light, temperature and the availability of nutrients.
Phytoplankton can adapt its photosynthetic activity to environmental conditions. This adaptation is species-dependent.