• Tropical plants use alternative forms of photosynthesis to adapt to climate conditions.Scott Gilbert/Stockbyte/Getty Images
  
  Photosynthesis processes enable plants to capture the sun's energy and use it to manufacture the materials that make up plant bodies. Light, water and carbon dioxide are the essential ingredients needed for photosynthesis to take place. When any one of these ingredients is lacking, photosynthesis rates decrease in an attempt to adapt to external conditions. The climate conditions in tropical regions require plants to adapt alternative forms of photosynthesis for growth and survival.
  
  

C4 Photosynthesis

• The chemical pathway plants use to convert light, water and carbon dioxide into glucose, which acts as food for the plants, is described by the number of carbons into which the carbon dioxide is incorporated at the beginning of the process. Over 90 percent of plants use C3 photosynthesis processes. An estimated 1 percent of plant species use C4 photosynthesis processes, according to the Encyclopedia of Earth. C4 processes use a four-carbon compound to synthesize light, water and carbon dioxide as opposed to the three-carbon compound used in C3 photosynthesis. Summer annual plants, corn, millet and tropical and subtropical grasses such as switchgrass and fourwing saltgrass use C4 photosynthesis processes to adapt to extremes in light and heat temperatures. These plant species are physically equipped to use alternative chemical processes, which enable them to capture and use light energy at faster rates than those produced by C3 photosynthesis. In addition, a specialized enzyme known as PEP carboxylase enables small air openings on leaf surfaces called stomata to absorb carbon dioxide gases much faster than during C3 processes. This prevents plants from becoming dehydrated and protects delicate leaf cells from light overexposure.
  
  

CAM Photosynthesis

• CAM processes are an alternative form of photosynthesis used by plants such as cacti, tropical orchids and bromeliads that reside under extremely humid and/or hot climate conditions. CAM stands for Crassulacean Acid Metabolism. Crassulaceans were the first plant family to use this alternate form of photosynthesis, which involves an acid metabolism process that stores carbon dioxide as an acid. The ability to store carbon dioxide as an acid enables these plants to absorb the gas at night when climate conditions are cooler, according to the Encyclopedia of Earth. Plant stomata openings can remain closed during the day, which prevents excess water loss and protects leaf cell structures from extreme light conditions. CAM photosynthesis also enables plants to shift into an idle mode during dry spells and to use carbon dioxide reserves to fuel needed photosynthesis processes.
  
  

Environmental Conditions

• A plant's environmental conditions, such as water availability, temperature and light intensity, determine the rate at which photosynthesis takes place. Photosynthesis mainly takes place along plant leaf surfaces, requiring plants to draw water up from the soil. Carbon dioxide gases enter through stomata. Stomata openings close under extreme light and heat conditions. This process protects plants from dehydration and damage to plant leaf cells. When stomata openings close up, carbon dioxide amounts decrease accordingly, causing photosynthesis rates to decline. This is why tropical plants use alternative methods of photosynthesis while conserving water and protecting leaf cells from overexposure to light.