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Though it is also called the "dark reaction", the Calvin cycle does not occur in the dark or during nighttime. This is because the process requires NADPH, which is short-lived and comes from light-dependent reactions. In the dark, plants instead release sucrose into the phloem from their starch reserves to provide energy for the plant.
In the nitrogen cycle, atmospheric nitrogen is converted by plants into usable forms such as ammonia and nitrates through the process of nitrogen fixation. These compounds can be used by other organisms, and nitrogen is returned to the atmosphere through denitrification and other processes.
Cellular respiration happens when a cell takes glucose and oxygen and uses it to produce carbon dioxide, energy, and water. This transaction is important not only for the benefit of the cells, but for the carbon dioxide output provided, which is key in the process of photosynthesis .
Climate change can also be used more broadly to include changes to the climate that have happened throughout Earth's history. [32] Global warming—used as early as 1975 [33] —became the more popular term after NASA climate scientist James Hansen used it in his 1988 testimony in the U.S. Senate. [34] Since the 2000s, climate change has ...
The nitrogen cycle is an important process in the ocean as well. While the overall cycle is similar, there are different players [40] and modes of transfer for nitrogen in the ocean. Nitrogen enters the water through the precipitation, runoff, or as N 2 from the atmosphere. Nitrogen cannot be utilized by phytoplankton as N
Phytoplankton need nitrogen in biologically available forms for the initial synthesis of organic matter. Ammonia and urea are released into the water by excretion from plankton. Nitrogen sources are removed from the euphotic zone by the downward movement of the organic matter. This can occur from sinking of phytoplankton, vertical mixing, or ...
This ability to avoid photorespiration makes these plants more hardy than other plants in dry and hot environments, wherein stomata are closed and internal carbon dioxide levels are low. Under these conditions, photorespiration does occur in C 4 plants, but at a much lower level compared with C 3 plants in the same
The CO 2 compensation point (Γ) is the CO 2 concentration at which the rate of photosynthesis exactly matches the rate of respiration. There is a significant difference in Γ between C 3 plants and C 4 plants: on land, the typical value for Γ in a C 3 plant ranges from 40–100 μmol/mol, while in C 4 plants the values are lower at 3–10 μmol/mol. Plants with a weaker CCM, such as C2 ...