Photosynthesis At 1000 ppm CO in measuring air, both the C3 and C4 plants had similar leaf photosynthetic rates around 60 μmol CO·m·s indicating the suppression of photorespiration in C3 plants. There are three main factors affecting photosynthesis and several corollary factors. The three main are: Total photosynthesis is limited by a range of environmental factors. These include the amount of light available, the amount of leaf area a plant has to capture light (shading by other plants is a major limitation of photosynthesis), rate at which carbon dioxide can be supplied to the chloroplasts to support photosynthesis, the availability of
Fractionation of carbon isotopes in oxygenic photosynthesis However, growth rate alone does not account for observed fractionation. The flux of CO into and out of a cell is roughly proportional to the cell surface area, and the cell carbon biomass varies as a function of cell volume. Phytoplankton geometry that maximizes surface area to volume should have larger isotopic fractionation from photosynthesis. The biochemical characteristics of phytoplankton are similar to C3 plants, whereas the gas exchange characteristics more closely resemble the C4 strategy. More specifically, phytoplankton improve the efficiency of their primary carbon-fixing enzyme, RuBisCO, with carbon concentrating mechanisms (CCM), just as C4 plants accumulate CO in