In my Jan 23 post, ‘why is it better to water plants in the morning”, we talked about the first phase of photosynthesis or the light dependent phase. Today, we will talk about the second phase of photosynthesis or the light-independent phase, also known as carbon fixation.
If sunlight and water are needed in the 1st phase, carbon dioxide and the energy produced from the 1st phase are the ones needed in this 2nd phase.
The end result of this carbon fixation phase is the formation of organic molecules especially carbohydrates.
Different plants use different ways of fixing carbon dioxide into organic molecules. The difference is dictated by the surrounding temperature.
Plants found in temperate regions or what are called C3 plants, generally use a 3-Carbon compound as their first molecule in the process. This process is also called Calvin cycle.
Plants in tropical regions on the other hand, use a preliminary 4-Carbon compound before it proceeds to the Calvin cycle. Plants using this process are therefore called C4 plants.
Finally, plants in desert areas cannot open their stomata (passage way for carbon dioxide) during daytime because they will lose too much water this way. They can thus take in carbon dioxide only at night. They store the carbon dioxide in organic acids at night and just transform these acids into carbohydrates during daytime. Plants belonging to this group include various cacti (singular, cactus) and are called CAM plants or Crassulacean Acid Metabolism plants.
Anyway, whichever process is used by plants to fix carbon dioxide, they still end up making organic compounds especially carbohydrates. These compounds are what we use as food.
So this gives us more reasons to thank green plants. Don’t you agree?